Merge branch 'master' into feature/dto-extensions

Co-authored-by: robin.bygrave <robin.bygrave@eroad.com>

docs/LIBRARY.md

@@ -54,7 +54,8 @@ Ebean is an ORM library for Java and Kotlin focused on relational data access, t
 | `exists()` | Efficient existence checks | `new QCustomer().email.equalTo(email).exists();` |
 | `findOne()` | Unique/single-row retrieval | `new QCustomer().id.equalTo(id).findOne();` |
 | `findList()` | List retrieval | `new QCustomer().findList();` |
-| `asDto(...).findList()` | DTO projection reads | `new QOrder().asDto(OrderSummary.class).findList();` |
+| `asDto(...).findList()` | Flat DTO projection reads | `new QOrder().asDto(OrderSummary.class).findList();` |
+| `mapTo(...).findList()` | Nested DTO graph projection reads | `new QCustomer().mapTo(CustomerDto.class).findList();` |
 
 ### Entity mapping and lifecycle annotations
 
@@ -188,6 +189,7 @@ database.save(customer);
 | Model entity beans correctly | [entity-bean-creation.md](guides/entity-bean-creation.md) |
 | Use Lombok safely with entities | [lombok-with-ebean-entity-beans.md](guides/lombok-with-ebean-entity-beans.md) |
 | Write type-safe query bean queries | [writing-ebean-query-beans.md](guides/writing-ebean-query-beans.md) |
+| Map nested entity graphs to DTO graphs | [mapping-entity-graphs-to-dtos.md](guides/mapping-entity-graphs-to-dtos.md) |
 | Persist changes and manage transactions | [persisting-and-transactions-with-ebean.md](guides/persisting-and-transactions-with-ebean.md) |
 | Build test entities quickly | [testing-with-testentitybuilder.md](guides/testing-with-testentitybuilder.md) |
 

docs/dto-mapping-design.md

@@ -0,0 +1,709 @@
+# Nested DTO Mapping — API Design
+
+Design spike for the accepted requirements in [dto-mapping-requirements.md](./dto-mapping-requirements.md),
+covering issue #2540. This captures the concrete API shape, annotations, and open-question decisions made
+during design review — before implementation begins.
+
+## Two source-vs-target mapping pipelines
+
+Ebean now has (or will have) two distinct DTO pipelines. It's important callers can tell which one they're
+using:
+
+1. **`asDto(Dto.class)`** (existing) — a `DtoQuery`, executed directly against a flat SQL `ResultSet`.
+   One row -> one DTO, via constructor/setter matching. No nested ToOne/ToMany support, no entity graph
+   involved.
+2. **`mapTo(Dto.class)`** (new) — runs the normal ORM entity query (joins/fetches as usual), producing an
+   *unmodifiable entity graph*, then maps that Java object graph into a DTO graph. Supports nested
+   ToOne/ToMany, identity-aware de-duplication, and derives its own fetch spec from the DTO shape.
+
+## Proposed API
+
+```java
+// Existing flat DtoQuery pipeline — unchanged
+new QUser().valid.eq(true)
+    .select(firstName, lastName)
+    .asDto(UserInfo.class)
+    .findList();
+```
+
+```java
+// NEW: nested DTO graph pipeline
+public class CustomerDto {
+  Long id;
+  String name;
+  AddressDto billingAddress;      // ToOne -> nested DTO, matched by property name "billingAddress"
+  List<ContactDto> contacts;      // ToMany -> nested DTO list, matched by property name "contacts"
+
+  @DtoPath("billingAddress.line1")
+  String billingLine1;            // renamed / flattened path
+}
+
+public class ContactDto {
+  Long id;
+  String firstName;
+  String lastName;
+
+  @DtoRef
+  Long customerId;                // id-only back-reference, avoids re-embedding CustomerDto (cycle)
+}
+
+List<CustomerDto> dtos = new QCustomer()
+    .status.eq(Status.ACTIVE)
+    .mapTo(CustomerDto.class)
+    .findList();
+```
+
+Computed values (e.g. `cityOrUnknown` derived from `coalesce(billingAddress.city, 'Unknown')`) are
+**not** modeled with a `@Formula2` annotation directly on the DTO - that was explored and rejected
+(see "Formula2-on-DTO scope" below). Instead they're modeled as a plain matching field on the DTO,
+sourced from an `@Entity @View` entity that itself carries the `@Formula2` - see "Computed/aggregate
+properties" below for the worked example.
+
+`mapTo(CustomerDto.class)`:
+- Introspects `CustomerDto` (recursively, at codegen time) to derive the `select(...)`/`.fetch(...)` spec
+  automatically from the DTO's declared shape.
+- Forces `setUnmodifiable(true)` under the hood — gives fail-fast + a cheap, non-mutable source graph
+  (satisfies the fail-fast requirement without a separate flag).
+- Runs the query, then runs a mapper over the resulting entity graph, de-duplicating DTO instances by id
+  for repeated nested references (identity-aware, mirrors the source entity graph's own de-duplication).
+
+## Decisions made
+
+### Fetch spec: auto-derived from DTO shape
+
+The DTO's declared structure (fields, nested DTO types, `@DtoPath` overrides) is the single source of truth
+for what gets selected/fetched from the database. Callers do not need to separately maintain a `.fetch(...)`
+spec in parallel with the DTO — this directly addresses the original issue's pain point (DTO and query
+projection drifting out of sync).
+
+### Entry point naming: `mapTo(Dto.class)`
+
+Chosen over `asGraph(...)` / `into(...)` / overloading `findList(Class)`. Reads clearly as "map the
+resulting entity graph to this DTO type" and is unambiguous against the existing `asDto(...)` (flat,
+SQL-row-based) mechanism.
+
+### Cycle handling: codegen-time DAG check + `@DtoRef` escape hatch
+
+Because the fetch spec and mapper are both derived from the *static* DTO type graph (not live object
+traversal), cycle detection is a compile-time/codegen-time concern, not a runtime one. This is stronger
+than the common approach in the ecosystem:
+
+- **MapStruct** does not auto-detect cycles. It offers an opt-in `@Context` "cycle guard" pattern (an
+  identity map of already-mapped source -> target objects) that the developer must wire up manually to
+  avoid infinite recursion mapping bidirectional object graphs.
+- **Blaze-Persistence / QueryDSL / JOOQ record mapping** avoid the problem architecturally: view/projection
+  types are required to be a strict tree; a back-reference is modeled as an id or a much shallower type,
+  never the same full view type again.
+
+Ebean's approach: fail the build at annotation-processing time if a DTO's declared type graph is not a DAG,
+with a clear error message. Provide `@DtoRef` as an explicit escape hatch for intentional back-references
+(e.g. `Contact.customer`) — it maps only the id, not the full nested DTO, breaking the cycle by design
+rather than by runtime guard.
+
+### `@DtoPath` / `@DtoRef`: parallels for readers coming from MapStruct or Blaze-Persistence
+
+Neither annotation is a novel concept - both map onto things MapStruct and Blaze-Persistence users will
+already recognise, which is worth spelling out explicitly so it's easy to "grok fast":
+
+- **`@DtoPath("billingAddress.line1")` is Ebean's equivalent of MapStruct's dot-path `source` flattening**
+  — e.g. `@Mapping(target = "line1", source = "billingAddress.line1")`. MapStruct auto-generates a
+  null-safe chain of getter calls for a dotted `source`; `@DtoPath` does exactly the same thing, just
+  declared on the DTO field itself rather than on a mapper method parameter list. It is also close to
+  Blaze-Persistence's `@Mapping("billingAddress.line1")` on an `@EntityView` attribute, which is a JPQL
+  path expression evaluated the same way — Blaze's placement (directly on the target view property) is
+  actually the closer analogue of the two, since Ebean's `@DtoPath` is likewise placed on the DTO field.
+  The difference from Blaze: `@DtoPath` is restricted to plain getter-chain navigation (no arbitrary JPQL/
+  SQL expression) - see "Formula2-on-DTO scope" below for the boundary and why full expression support is
+  deliberately deferred.
+- **`@DtoRef` has no dedicated equivalent in either tool** - both MapStruct and Blaze would express the
+  same "just the id" mapping as a plain dot-path to `.id` (`@Mapping(source = "customer.id")` / Blaze
+  `@Mapping("customer.id")`), with no special marker for it. What `@DtoRef` adds beyond that shorthand is
+  *intent*: it tells the codegen this property is a deliberate cycle-breaking reference, so (a) it adds
+  just the association's own name (not a dotted `.id` path) to the generated fetch spec's root
+  `select(...)` - reading the FK column directly with no join, and skipped entirely if that same
+  association is already fully fetched by a `NESTED_ONE`/`NESTED_MANY` property elsewhere on the same DTO
+  (see `DtoMapperWriter.fetchGroupChainCalls()`'s `case REF` branch) - and (b) it participates in the
+  codegen-time DAG cycle check above as an explicit "this is fine, don't flag it" signal, rather than
+  requiring a suppression escape hatch bolted on afterwards.
+
+  **Bug found and fixed while building the aggregation worked example below:** the original implementation
+  excluded `REF` properties from the fetch spec *entirely*, on the assumption the id is "already available
+  off an unfetched reference without triggering a fetch/lazy load". That assumption is only true when some
+  *other* property on the same DTO happens to also fetch that association (as was always the case in the
+  existing hand-built examples). Tested directly against a bare `@ManyToOne` with no other fetch of it:
+  accessing `.getCustomer().getId()` in that case triggers a full lazy-reload of the owning row (extra SQL,
+  not free) - and for an aggregation query it's worse, since the property being grouped by must be selected
+  or the query can't group correctly at all. Fixed so `REF` always contributes its association name to the
+  root `select(...)` (deduped against any existing `NESTED_ONE`/`NESTED_MANY` fetch of the same path).
+
+### Read-only entity memory overhead: `InterceptReadOnly`
+
+`setUnmodifiable(true)` isn't just a behavioural fail-fast flag - it also swaps the per-bean intercept
+implementation to `InterceptReadOnly`, which is deliberately minimal: just a `boolean[] loaded` (one flag
+per property) and a `boolean frozen`, plus the inherited owner reference and `fullyLoadedBean` flag. Compare
+to `InterceptReadWrite` (the mutable/updatable variant), which additionally carries a `ReentrantLock`, four
+transient collaborator references (`NodeUsageCollector`, `PersistenceContext`, `BeanLoader`,
+`PreGetterCallback`), a `byte[] flags` array (per-property loaded+changed+dirty+orig-value-set state),
+`Object[] origValues`, `Exception[] loadErrors`, `MutableValueInfo[]`/`MutableValueNext[]`, and several more
+scalar bookkeeping fields. None of that is needed for a bean that will only ever be read, so
+`setUnmodifiable(true)` graphs carry meaningfully less per-instance overhead than normal fetched entities -
+relevant here because `mapTo(Dto.class)` forces `setUnmodifiable(true)` on its underlying query, making the
+*source* graph for a DTO mapping cheaper than the equivalent normal (writable) entity graph would be.
+
+### Ad-hoc computed/formula properties: model as `@Entity @View`/`@Sql`, not ad-hoc SQL-on-DTO
+
+The "fully ad-hoc SQL-on-DTO" stretch goal above (closer to Blaze's arbitrary `@Mapping` expressions) doesn't
+need to be built as a bespoke DTO-annotation-processing feature. Ebean already supports modelling read-only,
+computed, or view-backed data as ordinary entities via `@Entity` + `@View` (backed by a SQL view, e.g. one
+with aggregates/computed columns) or `@Entity` + `@Sql` (backed by arbitrary `RawSql`, no base table). Given
+that, the Blaze-Persistence-style "an entity view attribute backed by an arbitrary SQL expression" need can
+usually be satisfied by:
+
+1. Modelling the computed/derived shape as its own `@Entity @View` (or `@Sql`) "read entity" - the SQL
+   expression/aggregation lives in the view definition, not in a new annotation-processed DTO mechanism.
+   `@View`'s `name()` doesn't have to point at a genuinely separate database view - it can just point at
+   an *existing* table (e.g. `@View(name = "contact")` on a second entity class reading the same table as
+   `Contact`) purely to mark the entity as view-like/read-only, in which case Ebean's DDL generator emits
+   **no new table or view at all** for it - it's just a second lens onto the same physical data.
+2. Mapping *that* entity into a plain DTO using the existing, already-implemented `@DtoMapping` machinery -
+   no ad-hoc-SQL-on-DTO support required, since there's no computed expression left to resolve at the DTO
+   layer at all; it's just another entity-to-DTO mapping.
+3. This read entity benefits from the same `setUnmodifiable(true)`/`InterceptReadOnly` memory efficiency
+   above when used purely as `mapTo(...)` input, so there's no meaningful cost to preferring this over a
+   hypothetical native ad-hoc-SQL-on-DTO feature.
+
+This significantly narrows (and may eliminate) the case for a dedicated ad-hoc-SQL-on-DTO mechanism - it
+remains listed as an open stretch goal below primarily for the case where a computed value's SQL is genuinely
+one-off/DTO-specific and not worth promoting to a standalone `@View`/`@Sql` entity.
+
+**Worked example** (`tests/test-dto-mapping`): `ContactSummary` is `@Entity @View(name = "contact")` (no new
+DDL - reads the same table as `Contact`) with `@Formula2("concat(firstName, ' ', lastName)")` computing
+`fullName`; `ContactSummaryDto` is a plain two-field DTO; `@DtoMapping(source = ContactSummary.class, target
+= ContactSummaryDto.class)` generates `ContactSummaryDtoMapper` exactly like any other entity→DTO pair - the
+formula property is just selected like any other field (`select("id,fullName")` in the generated
+`fetchGroup()`). See `TestContactSummaryDtoMapping`.
+
+### Aggregate/group-by computed properties: `@Sum`/`@Aggregation` as `@Entity @View`, same pattern
+
+Ebean's `@Sum` (shorthand for `@Aggregation("sum($1)")`) and `@Aggregation("count(...)"/"sum(...)"/"avg(...)"/
+"min(...)"/"max(...)")` are the group-by parallel to the formula pattern above - the same `@Entity @View`
+approach applies, just with an implicit `GROUP BY` instead of a per-row computed column. Ebean auto-derives
+the `GROUP BY` clause from whichever non-aggregate properties end up in the query's `select()`/`fetch()` - so
+a second `@Entity @View(name = <same base table>)` entity with one or more `@Sum`/`@Aggregation` properties
+plus a `@ManyToOne` grouping key becomes a per-parent rollup, with **no new table/view and no explicit
+`.groupBy()` call required**. This is Ebean's parallel to Blaze-Persistence entity view correlated aggregate
+mappings, e.g. `@Mapping("SIZE(contacts)")` / `@Mapping("SUM(contacts.engagementScore)")` on an `@EntityView`.
+
+**Nuance found while building the worked example, and since fixed: `@DtoRef` originally didn't fit the
+grouping key.** `@DtoRef` was originally excluded from the generated `select()`/`fetch()` spec entirely, on
+the premise that the id is already available off an unfetched reference for an ordinary entity graph. That
+premise doesn't hold for an aggregation query: the `@ManyToOne` *is* the property being grouped by, so if
+it's never selected, the query has nothing to group by. It turned out the premise didn't fully hold for
+ordinary entity graphs either - see the `@DtoRef` bug writeup above. Fixed so `@DtoRef` now adds the
+association's own name to the root `select(...)` (reading the FK column directly, no join) - which both
+supplies the grouping key here and fixes the general-case gap.
+
+**Worked example** (`tests/test-dto-mapping`): `ContactStats` is `@Entity @View(name = "contact")` (no new
+DDL - reads the same table as `Contact`/`ContactSummary`) with `@Aggregation("count(id)") contactCount` and
+`@Sum Integer engagementScore` (a new nullable field added to `Contact` purely to have something to sum),
+grouped by its `@ManyToOne customer`. `ContactStatsDto` is a flat 3-field DTO (`customerId`, `contactCount`,
+`engagementScore`), with `customerId` mapped via plain `@DtoRef`. The generated `ContactStatsDtoMapper`:
+
+```java
+this.fetchGroup = FetchGroup.of(ContactStats.class)
+  .select("customer,contactCount,engagementScore")
+  .build();
+...
+// skip DtoMapContext, only ever a top-level mapping
+return new ContactStatsDto(
+  (source.getCustomer() == null ? null : source.getCustomer().getId()),
+  source.getContactCount(),
+  source.getEngagementScore());
+```
+
+confirmed (via `LoggedSql`) to produce `select t0.customer_id, count(t0.id), sum(t0.engagement_score) from
+contact t0 ... group by t0.customer_id` - **no join**, one row per customer, correctly summed and counted.
+See `TestContactStatsDtoMapping`.
+
+### Formula2-on-DTO scope (v1): existing entity formulas only
+
+`@Formula2` on a DTO property in v1 only pulls in a formula **already declared on the source entity** (or
+a reachable associated entity) — it does not support fully ad-hoc SQL declared directly on the DTO with no
+matching entity property. Fully ad-hoc SQL-on-DTO (closer to Blaze's arbitrary `@Mapping` expressions) is a
+separate, larger stretch goal to revisit once the core graph-mapping mechanism is proven.
+
+**Attempted and rejected for v1.** A narrower version was implemented (`@Formula2(value)` resolved exactly
+like `@DtoPath` - a dot-path getter chain - plus a codegen-time validation that the resolved entity property
+is itself `@Formula2`/`@Formula`-annotated) but was rejected: for the common case (a DTO field with the same
+name as the entity's formula property) it generated **identical code to a plain unannotated field** - the
+only difference was the validation, which wasn't judged enough distinct value to justify a new annotation
+surface. Not implemented. The only way `@Formula2`-on-DTO would add real value is the full ad-hoc-SQL
+capability described above, which remains an open stretch goal.
+
+### Mapper implementation strategy: codegen, not reflection (native-image constraint)
+
+Native-image support is a core Ebean requirement, so the entity-graph -> DTO-graph mapper must not rely on
+runtime reflection or `MethodHandles`. This ruled out an initial reflection-based spike:
+
+- Ebean's existing flat `DtoQuery` (`DtoMetaConstructor`) already uses `MethodHandles` via
+  `Lookups.getLookup()`, but there is no `reflect-config.json` / native-image reachability metadata shipped
+  for it anywhere in the repo. That existing approach is not a clean precedent to copy for a bigger,
+  native-image-first feature.
+- Instead, the approach mirrors `querybean-generator`, which already generates real `.java` source for
+  `Q*` query bean types (not reflection) — consistent with the wider avaje-ecosystem convention
+  (avaje-inject / avaje-jsonb are explicitly reflection-free via compile-time codegen).
+
+**Implementation sequencing:** hand-write the mapper in the exact shape the annotation processor will
+eventually generate (plain Java, direct getter/constructor/setter calls, zero reflection) for one concrete
+example first, to validate the mapping algorithm and API shape quickly without ever introducing throwaway
+reflective code. That hand-written mapper then becomes the target/acceptance-test shape for the
+`querybean-generator` annotation processor that automates producing it.
+
+### Codegen target: Java first
+
+The mapper generation (requirement r2) targets `querybean-generator` (the existing APT module that already
+generates `Q*` query beans, reusing its `PropertyMeta` / `ProcessingContext` machinery). Kotlin parity via
+`kotlin-querybean-generator` is deferred to a later phase — not blocking initial delivery.
+
+### Mapper composition: one mapper per entity/DTO pair, generic `DtoMapper<SOURCE, TARGET>` interface
+
+Rather than one large mapper inlining every nested DTO type, each entity/DTO pair gets its own small
+mapper class - mirroring MapStruct's per-type mapper generation. All mappers implement a shared generic
+interface (prototyped as `org.tests.dtomapping.DtoMapper<SOURCE, TARGET>` in the spike, expected to move to
+`io.ebean` as a public type once solidified):
+
+```java
+public interface DtoMapper<SOURCE, TARGET> {
+  TARGET map(SOURCE source);
+  default List<TARGET> mapList(List<SOURCE> source) { ... }
+}
+```
+
+A parent mapper composes nested mappers via **constructor injection**, not a static singleton:
+
+```java
+public final class CustomerDtoMapper implements DtoMapper<Customer, CustomerDto> {
+  private final DtoMapper<Address, AddressDto> addressMapper;
+
+  public CustomerDtoMapper() {
+    this(new AddressDtoMapper());
+  }
+
+  public CustomerDtoMapper(DtoMapper<Address, AddressDto> addressMapper) {
+    this.addressMapper = addressMapper;
+  }
+
+  @Override
+  public CustomerDto map(Customer source) {
+    if (source == null) return null;
+    return new CustomerDto(source.getId(), source.getName(), addressMapper.map(source.getBillingAddress()));
+  }
+}
+```
+
+Rationale:
+- **Composability & reuse** - the same nested DTO type (e.g. `AddressDto`) used from multiple parent DTOs
+  reuses one generated mapper class rather than duplicating inline mapping logic.
+- **Constructor injection over static state** - avoids a global mutable singleton; a no-arg constructor
+  gives the common case (default nested mapper), while an overload accepting the nested mapper explicitly
+  allows substitution (tests, customization) without touching global state.
+- **Codegen-friendly** - this shape generates naturally: one top-level mapper class per DTO type, each
+  constructor-injecting the mappers for any nested DTO types it references.
+
+## ToMany collections and identity de-duplication (dto-spike-tomany-identity)
+
+Extending the spike (`ebean-test/src/test/java/org/tests/dtomapping/`) to a `Customer` with a
+`List<Contact> contacts` ToMany, where each `Contact` has a `customer` back-reference, surfaced
+two things worth recording.
+
+### The `DtoMapper` interface threads a shared context
+
+`DtoMapper<SOURCE, TARGET>` was extended so that mapping is always done against a `DtoMapContext`:
+
+```java
+public interface DtoMapper<SOURCE, TARGET> {
+  TARGET map(SOURCE source, DtoMapContext context);
+
+  default TARGET map(SOURCE source) {
+    return map(source, new DtoMapContext());
+  }
+
+  default List<TARGET> mapList(List<SOURCE> source, DtoMapContext context) { ... }
+
+  default List<TARGET> mapList(List<SOURCE> source) {
+    return mapList(source, new DtoMapContext());
+  }
+}
+```
+
+`DtoMapContext` is an identity-keyed cache of already-mapped source -> target instances, created
+once per top-level `mapList(...)`/`map(...)` call and threaded through every nested `map(...)`
+call. This lets repeated references to the *same* source entity instance - which Ebean's own
+persistence context already de-duplicates within one query (`contact.getCustomer() == customer`
+for the enclosing `Customer`, confirmed by an existing test) - map to the *same* target DTO
+instance, rather than each producing an equal-but-distinct copy. This is what makes the mapped
+DTO output "graph shaped" rather than "tree of copies shaped", and is required for r1/r3.
+
+### Bug found and fixed: the cache must be partitioned by target type, not just source identity
+
+The first cut of `DtoMapContext` was a single `IdentityHashMap<Object, Object>` keyed only by the
+source instance. This breaks as soon as the *same* source instance legitimately needs to map to
+*two different target types* within one graph - which happens immediately with a back-reference:
+
+- The top-level `CustomerDtoMapper` maps a `Customer` -> full `CustomerDto`.
+- The nested `ContactDtoMapper`, mapping `contact.getCustomer()` (the *same* `Customer` instance,
+  by identity), maps it -> shallow `CustomerRefDto` (the `@DtoRef`-style escape hatch that avoids
+  the `Customer -> Contact -> Customer` cycle).
+
+With a single un-partitioned identity map, whichever mapper runs first "wins" the cache slot for
+that `Customer` instance, and the other mapper incorrectly receives the wrong-typed cached result
+(a `ClassCastException` at best, silently wrong data at worst). This was caught by a failing test
+during the spike and fixed by partitioning the cache per target type:
+
+```java
+public final class DtoMapContext {
+  private final Map<Class<?>, Map<Object, Object>> mappedByType = new HashMap<>();
+
+  public <S, T> T computeIfAbsent(Class<T> targetType, S source, Function<S, T> mappingFunction) {
+    Map<Object, Object> mapped = mappedByType.computeIfAbsent(targetType, t -> new IdentityHashMap<>());
+    // ... existing/create/put ...
+  }
+}
+```
+
+Each generated mapper passes its own target DTO `Class` as the first argument, so `Customer ->
+CustomerDto` and `Customer -> CustomerRefDto` are cached independently even though the key
+(`Customer` instance) is identical. **This is an implementation detail the codegen must get
+right** - worth flagging explicitly when `dto-codegen-mapper` starts, since it's easy to
+regress if the generator is written from scratch without this test coverage in front of it.
+
+### Codegen optimization: skip the `DtoMapContext` cache for types that are never nested elsewhere
+
+`DtoMapContext.computeIfAbsent` only ever produces a cache *hit* when the exact same source
+instance is presented to `map()` more than once within one top-level call - which can only happen
+when the target type is reachable via more than one path in the graph, i.e. it's used as a
+`NESTED_ONE`/`NESTED_MANY` property by some *other* `@DtoMapping` pair (e.g. `CustomerRefDto`
+reached from many `Contact`s via a shared `Customer`, or `AddressDto` shared as `billingAddress`
+across customers). A type that's only ever a top-level `mapTo(...)`/`mapList(...)` entry point can
+never receive the same source instance twice within one call - Ebean's own query engine already
+de-duplicates root entity instances - so the cache lookup/insert there is pure overhead with a
+guaranteed-never-hit `IdentityHashMap`.
+
+Since all `@DtoMapping` pairs are resolved together at codegen time (`DtoMappingReader.
+resolveAndValidate()`), it's straightforward to compute this: after cycle exclusion, walk every
+surviving `DtoBeanMeta`'s properties and mark any `nested()` target as `nestedElsewhere()`. The
+generated `map()` method then branches per mapper:
+
+```java
+// CustomerDto - never nested by another mapper, only a mapTo()/mapList() entry point
+public CustomerDto map(Customer source, DtoMapContext context) {
+  if (source == null) return null;
+  // DtoMapContext for nested mappers only
+  return new CustomerDto(source.getId(), source.getName(),
+    billingAddressMapper.map(source.getBillingAddress(), context),
+    contactsMapper.mapList(source.getContacts(), context));
+}
+
+// AddressDto - nested under CustomerDto.billingAddress, so may be shared across customers
+public AddressDto map(Address source, DtoMapContext context) {
+  if (source == null) return null;
+  // dedup using DtoMapContext, same Address instance can be reached via more than one path in the graph
+  return context.computeIfAbsent(AddressDto.class, source, s -> new AddressDto(
+    s.getId(), s.getLine1(), s.getCity()));
+}
+
+// ContactSummaryDto - flat, top-level only, no nested children at all
+public ContactSummaryDto map(ContactSummary source, DtoMapContext context) {
+  if (source == null) return null;
+  // skip DtoMapContext, only ever a top-level mapping
+  return new ContactSummaryDto(source.getId(), source.getFullName());
+}
+```
+
+Deliberately terse, single-line comments - just enough for a developer skimming generated code (e.g.
+per the earlier `@Formula2`-on-DTO worked example) to know at a glance *why* a given mapper does or
+doesn't use the cache, without spelling out the full reachability argument inline every time (that
+lives here in the design doc instead). Note `CustomerDto`'s own construction skips the cache even
+though it *has* nested children - `context` is still threaded down to `billingAddressMapper`/
+`contactsMapper` since those target types (`AddressDto`, `ContactDto`) *are* nested elsewhere and
+still need the identity cache for themselves - hence the distinct "for nested mappers only" wording
+from the "only ever a top-level mapping" case (`ContactSummaryDto`), which has no children to thread
+a context to at all.
+
+### Fetching a ToOne back-reference used only for its FK/id needs the FK property fetched too
+
+Confirmed (via a first-cut test failure) that if a ToMany's element type has a ToOne back to its
+parent (e.g. `Contact.customer`), that FK property must itself be included in the fetch
+(`.fetch("contacts", "id,firstName,lastName,customer")`) even when the mapper only reads the id
+off the reference. Omitting it throws `LazyInitialisationException: Property not loaded:
+customer` on the `getCustomer()` call itself (not merely on a property access on the returned
+reference) - i.e. the earlier "ToOne reference access alone doesn't lazy load" finding
+(dto-validate-fetch-pagination) only holds once the ToOne/FK property is itself part of the
+fetch/select spec. This reinforces r6 (auto-deriving the fetch spec from DTO shape): the codegen
+must include a ToOne property in the fetch spec whenever a DTO needing it (even just its id) is
+reachable through a ToMany, not just at the top level.
+
+### Test coverage added
+
+- `TestCustomerDtoGraphMapping` extended to cover `contacts` ToMany mapping and to assert that
+  sibling `ContactDto`s under the same customer share the identical `CustomerRefDto` instance.
+- `TestContactDtoGraphMapping` (new) - standalone `ContactDtoMapper` test focused specifically on
+  the identity de-dup guarantee and null-source handling.
+
+## Codegen foundation: avaje-prisms adopted in querybean-generator (dto-codegen-mapper, step 1)
+
+Before writing the DTO-mapper annotation-processing logic itself, adopted `avaje-prisms`
+(`io.avaje:avaje-prisms`) in `querybean-generator` as the mechanism for reading the new
+`@DtoPath`/`@DtoRef` annotations at APT time, replacing what would otherwise be more hand-rolled
+`AnnotationMirror` walking (the existing pattern in `FindDbName.java`/`ReadModuleInfo.java`,
+left as-is/unmigrated - only the *new* annotations use prisms).
+
+This mirrors the proven pattern already used in two sibling projects in the same ecosystem -
+`avaje-inject`'s `inject-generator` and `avaje-jsonb`'s `jsonb-generator` - both declare
+`@GeneratePrism(SomeAnnotation.class)` once and get a generated `SomeAnnotationPrism` with
+`isPresent(element)` / `getInstanceOn(element)` / `getOptionalOn(element)` and typed accessors
+for every annotation member (correctly handling `Class`-valued members, avoiding the classic
+`MirroredTypeException` dance).
+
+Key property preserved: `querybean-generator` has **zero runtime/compile dependencies today**
+(confirmed via `mvn dependency:list` returning "none"), matching annotations by FQN string
+constants (`Constants.java`) rather than importing the actual annotation classes - deliberately
+keeping the processor free of any dependency footprint for consumers. Adding `avaje-prisms` (to
+generate the prism wrapper) and `ebean-annotation` (to reference `@DtoPath`/`@DtoRef` as literal
+`Class` values in `@GeneratePrism(...)`) as `optional` dependencies preserves this: `mvn
+dependency:list -DincludeScope=runtime` confirms every one of these (plus their own transitive
+deps: `avaje-prism-core`, `avaje-spi-service`, `avaje-spi-core`) is marked `(optional)`, so none
+of it propagates to a project that depends on `querybean-generator` (whether as a normal
+dependency or via `annotationProcessorPaths`).
+
+New annotations were added to the separate `ebean-annotation` repo (`io.ebean.annotation`
+package, alongside `@Formula2`), not this repo:
+
+```java
+@DtoPath("billingAddress.line1")
+String billingLine1;   // rename/flatten a DTO property from a nested source path
+
+@DtoRef
+Integer customerId;    // id-only back-reference, breaks what would otherwise be a graph cycle
+```
+
+Both use `@Target({FIELD, METHOD})` and `RetentionPolicy.CLASS` - visible to the annotation
+processor (including across module boundaries, since `CLASS` retention survives in the compiled
+`.class` file) but absent from runtime reflection, consistent with DTOs remaining plain,
+framework-free types with no runtime footprint.
+
+Wiring changes in `querybean-generator`:
+- `pom.xml`: added `avaje-prisms` (`optional`, plus `annotationProcessorPaths` entry) and
+  `ebean-annotation` (`optional`) dependencies; removed the previous `-proc:none` compiler arg
+  (which would have suppressed `avaje-prisms`' own processor from running to generate the prism
+  source) - annotation processing is now scoped to exactly `avaje-prisms` via the explicit
+  `annotationProcessorPaths` list, so no other processor is auto-discovered.
+- `module-info.java`: added `requires static io.avaje.prism;` and `requires static
+  io.ebean.annotation;` (`static` = compile-time only, matching the `optional` Maven scope).
+- New `package-info.java` declaring `@GeneratePrism(DtoPath.class)` and
+  `@GeneratePrism(DtoRef.class)`, generating `DtoPathPrism`/`DtoRefPrism` into
+  `target/generated-sources/annotations`.
+
+Verified: full `querybean-generator` build + existing test suite pass unchanged, and a downstream
+full rebuild (`ebean-test` with `-am`) - which exercises the existing Q-bean codegen - also
+passes with no regressions.
+
+### Trigger mechanism: `@DtoMapping(source, target)` on a neutral package-info.java
+
+Considered and rejected: putting a `source`/entity-referencing annotation directly on the DTO
+class itself (e.g. `@Dto(Customer.class)` on `CustomerDto`). Rejected because DTO types are
+often owned/generated elsewhere (e.g. from an OpenAPI spec) and must not be forced to reference
+an internal persistence/entity type - that would leak internal domain types into a
+public-facing/generated DTO module.
+
+Instead, adopted the same pattern `avaje-jsonb` uses for external/foreign types it doesn't own
+(`@Json.Import`): a repeatable annotation declared on a *neutral* holder - a `package-info.java`
+- naming the `source` entity and `target` DTO as a pair:
+
+```java
+@DtoMapping(source = Customer.class, target = CustomerDto.class)
+@DtoMapping(source = Contact.class, target = ContactDto.class)
+package org.example.dto;
+```
+
+`@DtoMapping` (new, in `ebean-annotation`) is `@Target({PACKAGE, MODULE})`,
+`@Retention(SOURCE)` (pure codegen trigger, never needed at runtime - unlike `@DtoPath`/
+`@DtoRef` which need `CLASS` retention to remain visible to the DTO field itself),
+`@Repeatable(DtoMapping.List.class)` following Java's own repeatable-annotation idiom. Neither
+the entity nor the DTO needs any annotation of its own.
+
+**Generated mapper package placement** - also modeled directly on `avaje-jsonb`'s handling of
+`@Json.Import` for external types (`AdapterName`/`ProcessingContext.isImported`): defaults to the
+target DTO's own package, *unless* the source or target type belongs to a different Java module
+than the one being processed, in which case the generated mapper is placed in a package derived
+from the processing module's own name instead - avoiding a JPMS "split package" violation that
+would occur from generating source into a package owned by another module. An explicit
+`mapperPackage` attribute is available to override this for edge cases. Same-module (or
+non-modular/unnamed-module) projects are unaffected and just get the mapper alongside the DTO.
+
+### mapTo(Class) dispatch: Class-token API + generated compile-time-safe registry
+
+The original API sketch above (`mapTo(CustomerDto.class)`) predates the native-image/no-reflection
+decision. Rather than switching to an instance-based API (`mapTo(new CustomerDtoMapper())`),
+decided to keep the `Class`-token shape and generate a compile-time-safe registry to resolve it -
+no reflection, no `Class.forName`, just literal `Class` comparisons generated at build time, e.g.:
+
+```java
+<S, D> DtoMapper<S, D> mapperFor(Class<S> sourceType, Class<D> targetType) {
+  if (sourceType == Customer.class && targetType == CustomerDto.class) {
+    return (DtoMapper<S, D>) new CustomerDtoMapper();
+  }
+  if (sourceType == Contact.class && targetType == ContactDto.class) {
+    return (DtoMapper<S, D>) new ContactDtoMapper();
+  }
+  return null;
+}
+```
+
+Dispatch is keyed on the **(source, target) pair**, not target alone - this matches how
+`@DtoMapping(source, target)` pairs are declared, allows the same DTO type to be mapped from more
+than one source entity without ambiguity, and lets `query.mapTo(dtoType)` fail fast with a clear
+`PersistenceException` (rather than an incorrect match) when `query.getBeanType()` doesn't pair
+with the requested DTO.
+
+This mirrors the existing, already-proven `EbeanEntityRegister`/`EntityClassRegister` mechanism
+(`SimpleModuleInfoWriter.java`) that `querybean-generator` already generates per module for entity
+classes - a `List<Class<?>>` built from literal `SomeEntity.class` references, registered via
+`META-INF/services` (`ServiceLoader`, itself native-image-friendly with no extra reflection
+config needed for simple no-arg-constructor implementations). The DTO mapper registry follows the
+same per-module aggregation + `META-INF/services` registration shape, giving `mapTo(Class)` a
+concrete generated implementation to dispatch through at runtime without reflection anywhere in
+the chain.
+
+### mapTo(Dto.class) runtime wiring (implemented)
+
+`query.mapTo(dtoType)` returns a `MappedQuery<D>` (`findList()`/`findOne()`/`findOneOrEmpty()`/
+`findStream()`/`findPagedList()`/`usingMaster(boolean)`/`usingTransaction(Transaction)`/`usingConnection(Connection)`).
+On first use it resolves the generated `DtoMapper<S, D>` for the query's `(getBeanType(), dtoType)`
+pair via a `DtoMapperManager` (a `ServiceLoader`-backed aggregator over all generated
+`DtoMapperRegister`s, analogous to `DtoBeanManager`), then:
+
+- applies `mapper.fetchGroup()` to the query via `query.select(fetchGroup)` - the fetch/select spec
+  is entirely derived from the DTO's declared shape, no manual `.select()`/`.fetch()` needed;
+- forces `query.setUnmodifiable(true)` - the resulting entity graph is read-only input to the
+  mapper, and any DTO property whose source wasn't actually fetched fails fast with
+  `LazyInitialisationException` rather than silently lazy loading or returning `null`;
+- executes the query and maps the result(s) via `mapper.map(...)`/`mapper.mapList(...)`.
+
+An unregistered `(source, dtoType)` pair throws a `PersistenceException` with a suggested
+`@DtoMapping` fix, at first use (i.e. `findList()`/`findOne()`), not at `mapTo(dtoType)` call time.
+
+`MappedQuery<D>.usingMaster(boolean)`, `.usingTransaction(Transaction)`, and `.usingConnection(Connection)`
+all delegate directly to the underlying entity query, mirroring `Query`/`QueryBuilder`. This lets a
+caller retry against the master data source after a read-replica failure by calling
+`usingMaster(true)` on the *same* `MappedQuery` instance and re-invoking a find method - there's no
+need to rebuild the query and call `.mapTo(...)` again.
+
+`MappedQuery<D>.findStream()` mirrors `QueryBuilder#findStream()` - the underlying entity query is
+streamed (supporting very large result sets, potentially using multiple persistence contexts
+internally) and each entity is mapped to its target DTO lazily as the stream is consumed. One
+`DtoMapContext` is shared across the whole stream (not per-element), so identity de-duplication of
+nested DTOs (e.g. several `Contact`s sharing the same `Customer`) still holds even when the source
+entities are never materialized into one `List` at all. As with the entity-level `findStream()`,
+callers must consume it via try-with-resources to ensure the underlying resources are closed.
+
+
+## Still open / to revisit during implementation
+
+- Whether `.fetch(...)` calls can still be layered on top of a `mapTo(Dto.class)` query for explicit
+  overrides. Currently the mapper's `fetchGroup()` is the *only* source of the fetch spec - any
+  `.select()`/`.fetch()` calls made before `.mapTo(...)` are overwritten by it.
+- Whether `@DtoPath`/`@DtoRef` need additional attributes beyond a bare path/marker (e.g. an explicit
+  target type on `@DtoRef` for disambiguation) once real DTOs with more complex shapes are codegen'd.
+- Behavior when a DTO property has no matching entity property and no `@DtoPath`/`@Formula2` override
+  (fail at codegen time, most likely, consistent with the "fail fast" philosophy).
+- `@Formula2`-on-DTO mapping to Blaze-Persistence/QueryDSL-style computed properties - not yet
+  implemented (see requirements doc); a narrower validation-only variant was attempted and rejected
+  as not distinct enough from `@DtoPath` (see "Formula2-on-DTO scope" above). The broader ad-hoc-SQL
+  case likely doesn't need a dedicated DTO feature at all - see "Ad-hoc computed/formula properties"
+  above for the `@Entity @View`/`@Sql` alternative.
+- **Fetch-path collision between a `NESTED_ONE`/`NESTED_MANY` property and a `@DtoPath` property -
+  found and fixed**: `DtoMapperWriter.fetchGroupChainCalls()` builds one `.fetch(path, ...)`
+  chain-call per distinct fetch path, but the underlying `OrmQueryDetail.fetch(...)` unconditionally
+  **overwrites** (rather than merges) any existing entry for the same path key. If a DTO declared a
+  `NESTED_ONE`/`NESTED_MANY` property AND a `@DtoPath` property whose fetch-path prefix is the *exact
+  same* path (e.g. a nested `AddressDto billingAddress` alongside `@DtoPath("billingAddress.line1")`
+  on the same DTO - both resolve to fetch path `"billingAddress"`), the generator would emit two
+  `.fetch("billingAddress", ...)` calls and the second would silently discard the first's selected
+  properties. Merging wasn't practical - the nested property's `.fetch(path, mapper.fetchGroup())`
+  call passes another mapper's own pre-built, immutable, shared `FetchGroup`, so there's no clean way
+  to splice an extra scalar property into it at the call site. Fixed instead with a **fail-fast
+  compile-time error**: `DtoMapperWriter` now detects the collision and raises a clear
+  `ctx.logError(...)` (annotation-processor `ERROR` diagnostic, fails the compile) naming the
+  colliding property and fetch path, and suggesting the two ways out - move the property onto the
+  nested DTO type instead, or pick a `@DtoPath` that reaches a different, non-colliding path (as
+  `ContactDto.customerCity` already does deliberately, per its own comment, using a 3-segment path).
+  Verified empirically by compiling a small reproduction with a colliding `@DtoPath` and confirming
+  the expected error fires; a permanent regression test
+  (`DtoMapperFetchPathCollisionTest` in `querybean-generator`) now runs this same repro directly
+  through `javax.tools.JavaCompiler` with the `Processor` registered, asserting the compile fails with
+  the expected diagnostic message.
+- **Compile-time verification of `select(...).asDto(...)` (r6, aspirational) - explored and closed as
+  rejected**: raw SQL is an opaque `String` at compile time, and even the typed query-bean
+  `.select(...)` form only type-checks against the *entity* - the match to the target DTO's constructor
+  still happens at runtime via reflection (`DtoQueryPlanConstructor`), and the `.asDto(...)` call site
+  can be arbitrarily distant from the `.select(...)` call, so there's no fixed AST shape an annotation
+  processor could reliably verify (unlike QueryDSL, whose compile-time safety actually comes from typed
+  `Projections.constructor(...)`/generated Q-type constructor calls, not from checking a select-list
+  against a DTO). `mapTo(Dto.class)` already closes the underlying gap in the tractable direction - it
+  derives the select/fetch spec *from* the DTO's declared shape at APT time, so it is compile-time safe
+  by construction. Recommend `mapTo()` whenever compile-time-checked DTO projection matters, and treat
+  `asDto()`/`findDto()` as the flexible, runtime-checked escape hatch for raw/dynamic SQL. See
+  `dto-mapping-requirements.md` requirement r6.
+- **Custom property conversion (`@DtoConvert`/`@DtoMixin`, r13/r14) - implemented**: motivated by a
+  real hand-written mapper (`DriverMapper`, central-access) needing both a dependency-free scalar
+  coercion (`short` -> `boolean`) and a dependency-backed conversion (AES decryption via an injected
+  cipher). Final design (see `dto-mapping-requirements.md` section E), as built:
+  - `@DtoConvert(value = ConverterType.class, method = "name")` on a DTO property (combinable with
+    `@DtoPath`); the generator dispatches on whether the referenced method is `static` - static means a
+    direct inlined static call (no registration, covers common reusable coercions), instance means
+    dispatch via a new `DtoConverterManager.get(ConverterType.class).method(...)` call, with the
+    resolved instance wired as a real constructor parameter/field on the generated mapper (same shape
+    as existing nested-mapper constructor injection). Multiple properties on the same mapper sharing
+    the same converter type are deduplicated to a single constructor parameter/field
+    (`DtoBeanMeta.converterDeps()`).
+  - `DtoConverterManager` (`ebean-api`, `io.ebean` package) is a small, narrowly-scoped static put/get
+    bridge - the app registers an already-DI-constructed converter singleton (e.g. built by
+    avaje-inject) *before* building the `Database`. This is a deliberate, narrow exception to the
+    general no-static-mutable-state convention: `ServiceLoader`-discovered, no-arg-constructed
+    generated code (`EbeanDtoMapperRegister`) has no other way to reach an already-DI-constructed
+    singleton. `DtoConverterManager.get(type)` throws immediately if nothing was registered for that
+    type, so a missing converter fails fast at Database-startup time (an eager field initializer on
+    `EbeanDtoMapperRegister`, and equally on each mapper's own no-arg constructor, which resolves the
+    same way via `DtoConverterManager.get(...)` for standalone/test construction), not lazily on first
+    use - `DtoMapperRegister`'s `mapperFor(...)` signature and `DtoMapperManager` are otherwise
+    completely unchanged, as originally planned.
+  - Two alternatives were explored and rejected first: (a) a `DtoMapContext.service(Class)` lookup -
+    wrong lifetime, `DtoMapContext` is a short-lived per-call identity-cache only; (b) a
+    `ServiceLoader`-discovered `DtoConverterSource` SPI mirroring `DtoMapperRegister` itself - can't
+    bridge to an *already* DI-constructed dependency without reconstructing/duplicating it.
+  - `@DtoMixin(Target.class)` - a companion type overlaying `@DtoPath`/`@DtoConvert`/`@DtoRef`
+    annotations onto a DTO that can't be annotated directly (e.g. OpenAPI-generated). Discovered via
+    `roundEnv.getElementsAnnotatedWith(...)` (added to `Processor.getSupportedAnnotationTypes()`,
+    since - unlike `@DtoPath`/`@DtoRef`/`@DtoConvert` - a mixin doesn't annotate an already-iterated
+    field of a known `@DtoMapping` target, so it can't be found lazily). `DtoMappingReader` resolves
+    each target property's annotations from the field itself first, falling back to a same-named
+    method on the registered mixin (`DtoMappingReader.prismOn(...)`) - directly mirrors avaje-jsonb's
+    proven `@Json.MixIn` mechanism.
+  - Implemented in `ebean-annotation` (`DtoConvert`, `DtoMixin`), `ebean-api` (`DtoConverterManager`),
+    and `querybean-generator` (`DtoConverterMeta`, `DtoBeanMeta.converterDeps()`,
+    `DtoMappingReader`/`DtoMapperWriter`/`DtoMapperRegisterWriter` changes). Test coverage:
+    `tests/test-dto-mapping` `TestDtoConvert` (static + instance dispatch, fail-fast unregistered-type
+    check) and `TestDtoMixin` (mixin overlay, including instance-dispatch conversion resolved purely
+    from mixin-declared annotations). The instance-dispatch converter is registered via a
+    `DatabaseConfigProvider` (ServiceLoader hook run before the `Database` is built) rather than a test
+    `@BeforeAll`, since `EbeanDtoMapperRegister`'s mapper fields (including any needing
+    `DtoConverterManager`) are all constructed eagerly during `Database` startup, which can be
+    triggered by whichever test class in the module happens to run first.
+
+
+## References
+
+- Requirements: [dto-mapping-requirements.md](./dto-mapping-requirements.md)
+- Issue: https://github.com/ebean-orm/ebean/issues/2540
+- MapStruct cycle mapping: https://mapstruct.org/documentation/stable/reference/html/#mapping-object-cycles

docs/dto-mapping-requirements.md

@@ -0,0 +1,270 @@
+# Nested DTO Mapping — Requirements
+
+Design requirements distilled from [issue #2540 "Support nested DTO mapping"](https://github.com/ebean-orm/ebean/issues/2540),
+reviewed against comparable features in QueryDSL (`@QueryProjection`) and Blaze-Persistence (`@EntityView`).
+
+## Context
+
+Ebean already supports:
+
+- Partial/flat DTO queries via `DB.findDto(...)` and `query.select(...).asDto(Dto.class)`.
+- `@Formula` / `@Formula2` — path-based, auto-joined computed SQL expressions, but only on managed entities.
+- `query.setUnmodifiable(true)` — builds a read-only, non-lazy-loading entity graph (`InterceptReadOnly`,
+  see PR #2626). Accessing an unloaded property throws `LazyInitializationException`; mutating throws
+  `UnmodifiableEntityException`.
+
+Unlike Hibernate, Ebean does dirty-detection on the bean itself (no dynamic proxies), so there is very little
+extra cost to an entity-graph query versus a DTO query. This makes an **unmodifiable entity graph** a cheap,
+natural intermediate representation to map *from* when producing a DTO graph — we don't need Blaze/Hibernate's
+proxy-based `EntityView` mechanism to get the performance benefit they are chasing.
+
+The goal is nested DTO graph support (DTOs containing ToOne/ToMany child DTOs), not just today's flat DTOs,
+while keeping DTOs as plain, framework-unattached classes.
+
+## Accepted Requirements
+
+### A. Nested DTO graphs
+
+- **Support nested DTO graphs (ToOne/ToMany)**
+  Allow mapping a query result into a DTO graph where DTO fields are themselves DTOs (ToOne) or
+  `List`/`Set<Dto>` (ToMany), not just flat DTOs. Use the existing `setUnmodifiable(true)` entity graph as
+  the intermediate, de-duplicated, identity-consistent source to map from.
+  *Inspiration: Blaze `@EntityView` subviews/subview collections; Jimmer fetcher DTOs.*
+
+- **Auto-generated entity → DTO graph mapper**
+  Given an unmodifiable entity graph plus a target nested DTO type, generate (via annotation processing,
+  reflection-free) a mapper that walks the graph and populates the DTO graph, matching properties by
+  name/type with override annotations for renames, computed values, and collection element types.
+  *Inspiration: Blaze `@EntityView` + subview mapping; conceptually similar to MapStruct but Ebean-generated
+  and graph/identity aware.*
+
+- **Identity-aware de-duplication in nested collections**
+  When mapping nested collections referencing the same underlying entity instance multiple times, reuse the
+  same DTO instance (mirrors Blaze/Jimmer identity semantics) rather than producing independent copies.
+  *Inspiration: Blaze/Jimmer identity handling.*
+
+### B. Formula-style DTO annotations
+
+- **`@Formula2`-like annotations on DTO fields**
+  Bring the existing `@Formula` / `@Formula2` concept (auto-joined, path-based computed SQL expressions) to
+  DTO classes so a DTO field can request a computed/aggregated value with the join auto-derived, instead of
+  only being available on managed entities.
+  *Inspiration: User suggestion; Ebean `@Formula2`; Blaze `@Mapping` computed expressions.*
+  *Status: a narrower version (pulling in an existing entity-level `@Formula2` by path) was implemented and
+  then rejected - for the common same-name case it generated code identical to a plain unannotated field, so
+  the annotation added no real value beyond a codegen-time validation. See `docs/dto-mapping-design.md`
+  ("Formula2-on-DTO scope" and "Ad-hoc computed/formula properties" sections). The broader goal - arbitrary
+  ad-hoc computed SQL on a DTO field - is better served by modelling the computed value as its own
+  `@Entity @View`/`@Sql` read entity and mapping *that* into a plain DTO, reusing the existing (already
+  accepted) nested-DTO mapping machinery rather than a new DTO-level annotation.
+
+- **Path-based property mapping annotation on DTO**
+  Allow a DTO field or constructor param to be annotated with a source path expression (e.g. `parent.name`)
+  so Ebean can auto-derive the select clause plus joins for nested/renamed properties, reducing manual
+  constructor wiring for non-trivial mappings.
+  *Inspiration: Blaze `@Mapping`; QueryDSL constructor expressions.*
+
+### C. Compile-time safety
+
+- **Compile-time verification of `select(...).asDto(...)` mapping** *(explored, rejected as impractical -
+  `mapTo()` accepted as the alternative)*
+  Today `select(props).asDto(Dto.class)` is only checked at runtime. Explored an annotation-processor
+  based mechanism to verify at compile time that selected properties match the DTO constructor or setters,
+  mirroring QueryDSL's `@QueryProjection` compile-time Q-type generation. Rejected as impractical: raw SQL
+  is an opaque `String` at compile time, and even the typed query-bean `.select(...)` form only
+  type-checks against the *entity* - the match to the target DTO still happens at runtime via reflection
+  (`DtoQueryPlanConstructor`), and the `.asDto(...)` call site can be arbitrarily distant from the
+  `.select(...)` call, so there's no fixed AST shape an annotation processor could reliably verify.
+  QueryDSL's actual compile-time safety comes from a different mechanism entirely - typed
+  `Projections.constructor(...)`/generated Q-type constructor calls, not from checking an
+  independently-built select-list against a DTO. `mapTo(Dto.class)` (see section A) already closes the
+  underlying gap in the opposite, tractable direction: it derives the select/fetch spec *from* the DTO's
+  declared shape at APT time, so it is compile-time safe by construction, with no separate select-list to
+  drift out of sync. Recommendation: document `mapTo()` as the compile-time-safe answer for DTO
+  projections, and treat `asDto()`/`findDto()` explicitly as the flexible, runtime-checked escape hatch
+  for raw/dynamic SQL.
+  *Inspiration: QueryDSL `@QueryProjection` compile-time Q-type generation.*
+
+- **Fail-fast on unmapped or lazy property access**
+  Ensure a clear, documented, minimal-ceremony way to fail fast if code touches a property not included in
+  the query projection, instead of silently lazy loading or returning null. `query.setUnmodifiable(true)`
+  already satisfies this (throws `LazyInitializationException`) — document/promote it as the answer, and
+  evaluate whether a lighter-weight flag decoupled from full unmodifiable/read-only semantics is needed.
+  *Inspiration: Original issue ask; already solved via `setUnmodifiable()` (PR #2626 `InterceptReadOnly`).*
+
+### D. Fetch strategy and performance
+
+- **Fetch strategy control for DTO graph relationships**
+  Existing entity query fetch hints (join vs. select/subselect secondary query, `+query`/`+lazy`) should
+  transparently carry over when the target of the query is a DTO graph rather than an entity graph.
+  `query.mapTo(Dto.class)` applies the DTO-derived `FetchGroup` only when the query has no
+  `select()`/`fetch()` already set - a manually tuned fetch spec always takes precedence and is never
+  overridden, allowing manual query optimisation when needed (at the cost of falling back to the
+  existing fail-fast-on-unmapped-property behaviour if the manual spec doesn't cover what the DTO needs).
+  *Inspiration: Blaze FETCH/SELECT/SUBSELECT fetch strategies.*
+
+- **Pagination support for DTO graph queries**
+  Confirm existing pagination works unchanged when projecting into nested DTO graphs.
+  *Inspiration: Blaze pagination and keyset pagination support.*
+
+### E. Custom property conversion
+
+- **Per-property custom scalar conversion (`@DtoConvert`)**
+  Motivated by real hand-written mapper code (`DriverMapper`, central-access) doing per-property scalar
+  coercion (`short` -> `boolean`) and dependency-backed conversion (AES decryption via an injected cipher).
+  Introduce a `@DtoConvert(value = ConverterType.class, method = "name")` annotation (combinable with
+  `@DtoPath` for source-getter override) on a DTO property. The generator dispatches based on whether the
+  referenced method is `static`:
+  - **Static method** -> a direct static call is inlined (`ConverterType.method(source.getX())`), zero
+    ceremony, no registration - covers common, reusable, dependency-free scalar coercions (e.g.
+    `short`/`boolean`, enum <-> `String`) that could apply across many unrelated entity/DTO pairs.
+  - **Instance method** -> dispatched via `DtoConverterManager.get(ConverterType.class).method(source.getX())`
+    and wired as a real constructor parameter/field on the generated mapper (same shape as existing
+    nested-mapper constructor injection) - covers conversions needing a real dependency (e.g. a cipher).
+  `DtoConverterManager` is a small, deliberately-scoped static put/get bridge: the app registers an
+  already-DI-constructed converter singleton (e.g. built by avaje-inject) *before* building the `Database`.
+  This is a narrow, accepted exception to the general no-static-mutable-state convention - it exists solely
+  to bridge an already-DI-constructed singleton into `ServiceLoader`-discovered, no-arg-constructed generated
+  code, which cannot otherwise reach a DI container. `DtoConverterManager.get(type)` throws immediately if
+  nothing was registered, so a missing converter fails fast at Database-startup time (an eager field
+  initializer on the generated `EbeanDtoMapperRegister`), not lazily on first use.
+  *Design exploration considered and rejected two alternatives first: (a) a `DtoMapContext.service(Class)`
+  lookup - rejected because `DtoMapContext` is a short-lived per-call identity-cache only, wrong lifetime for
+  a real singleton dependency; (b) a `ServiceLoader`-discovered `DtoConverterSource` SPI mirroring
+  `DtoMapperRegister` itself - rejected because a `ServiceLoader`-instantiated (no-arg) source cannot bridge
+  to an *already* DI-constructed dependency (e.g. a cipher needing config/secrets) without reconstructing it
+  itself, duplicating/bypassing the app's own DI-managed instance.*
+  *Inspiration: `DriverMapper` (central-access) hand-written pattern; MapStruct qualified converter methods.*
+  *Status: implemented - `@DtoConvert` (ebean-annotation), `io.ebean.DtoConverterManager` (ebean-api), and
+  querybean-generator codegen support (static/instance dispatch, constructor wiring deduplicated by converter
+  type). Test coverage: `tests/test-dto-mapping` `TestDtoConvert`.*
+
+- **`@DtoMixin` for DTOs that cannot be annotated directly**
+  Some DTOs are generated (e.g. from an OpenAPI spec) and not editable/annotatable, so `@DtoPath`/
+  `@DtoConvert`/`@DtoRef` cannot always be placed directly on the DTO. Introduce a `@DtoMixin(Target.class)`
+  companion interface/type, discovered by scanning the compilation round and overlaying its per-property
+  annotations onto the real target's properties by name-match - directly mirrors avaje-jsonb's
+  `@Json.MixIn` mechanism (`KingfisherMixin`/`CrewMateMixIn` pattern), a proven prior-art solution to the
+  exact same "can't annotate a generated/unowned type" problem.
+  *Inspiration: avaje-jsonb `@Json.MixIn`.*
+  *Status: implemented - `@DtoMixin` (ebean-annotation) and querybean-generator round-scanning/overlay
+  support (matches mixin methods to target properties by name, applying whichever of `@DtoPath`/`@DtoRef`/
+  `@DtoConvert` is present as if declared on the target field itself). Test coverage: `tests/test-dto-mapping`
+  `TestDtoMixin`.*
+
+### F. DI-friendly manual mapper usage
+
+- **Public `DtoMapperManager` with `get(Class<T> mapperType)` for DI**
+  Motivated by `DriverMapper`/`DriverService` (central-access): `DriverMapper` is a hand-written
+  `@Component` constructor-injected into `DriverService`. Moved `DtoMapperManager` from internal
+  (`io.ebeaninternal.server.dto`) to public `io.ebean` - unchanged `mapperFor(source, dto)`, plus a new
+  `get(Class<T> mapperType)` keyed by the generated mapper's own concrete class (e.g.
+  `manager.get(CustomerDtoMapper.class)`), for direct/concrete-typed DI injection. `DtoMapperRegister`
+  gained a default `mapperOfType(Class<T>)` method (non-breaking); the generator emits the real if-chain
+  body (mirrors `mapperFor`'s if-chain). `DtoMapperManager` has zero `Database` dependency (constructor
+  only does `ServiceLoader.load(DtoMapperRegister.class)`), so it can be constructed standalone,
+  independent of/before a `Database` - e.g. as an avaje-inject bean.
+  *Inspiration: `DriverMapper`/`DriverService` (central-access).*
+  *Status: implemented.*
+
+- **`DtoMapperManager` sharing via `DatabaseBuilder.putServiceObject`**
+  So `query.mapTo()` and application-injected mappers share the exact same `DtoMapperManager` instance
+  (and hence the same underlying generated mapper singletons) rather than each independently constructing
+  its own, `InternalConfiguration` checks `config.getServiceObject(DtoMapperManager.class)` first (mirrors
+  the existing `AutoMigrationRunner`/`GeoTypeProvider` `putServiceObject`/`getServiceObject` pattern),
+  falling back to constructing a default `new DtoMapperManager()` if none was supplied.
+  *Inspiration: user proposal following `DriverMapper`/`DriverService` review.*
+  *Status: implemented.*
+
+*Rejected: generator-emitted `builder(source)` method* - `DriverMapper` exposes `builder(cDriver)`
+returning a partially-populated `DriverBuilder` so callers can add extra caller-supplied fields (e.g.
+fleets) before `build()`. Rejected as a generator feature - `Driver`/`DriverSummary` already use
+avaje-recordbuilder's `@RecordBuilder`, which generates `Target.builder(existingInstance)`
+(seed-from-instance). The same effect is already achievable with zero ebean changes:
+`mapper.map(source)` then `Builder.builder(mapped).extraField(x).build()`. Documented as a recipe
+instead (see "Recipe: adding extra caller-supplied fields after mapping" in
+`docs/guides/mapping-entity-graphs-to-dtos.md`).
+
+### G. Large-target construction and shape variants
+
+- **Builder-based target construction for large DTOs**
+  Motivated by `UserService`/`User` (central-access): `User` is a 24-field OpenAPI-generated record with
+  a `@RecordBuilder`-generated `UserBuilder`, hand-mapped via a long fluent builder chain rather than a
+  positional constructor to stay readable/refactor-safe. The generator auto-detects a RecordBuilder-style
+  builder on the target (static `Target.builder()` + fluent per-property setters + `build()`) and uses
+  `Target.builder().prop(x)....build()` instead of `new Target(a, b, c, ...)` whenever (a) a builder is
+  detected and (b) the target has more than a threshold number of properties (default 5), falling back to
+  the positional constructor otherwise. An explicit `@DtoMapping` attribute (`builder = AUTO | ALWAYS |
+  NEVER`) overrides the heuristic in either direction. Applies regardless of whether the target class is
+  hand-authored or foreign/generated (e.g. an OpenAPI record) - `@DtoMapping` is already declared
+  externally via `package-info.java`, not on the target class, so this was already compatible with
+  foreign target types.
+  *Inspiration: `UserService`/`User` (central-access).*
+  *Status: implemented.*
+
+- **Named mapper variants excluding nested paths, sharing one generated class**
+  Motivated by `UserService`/`User` (central-access): `CUser` -> `User` is mapped in two shapes - with
+  nested `fleets` (`findUserByGid`) and without (`findAll`, bulk listing) - to avoid an unnecessary
+  join/fetch on the common bulk-listing path. Keeps the existing "shape always derived from declaration,
+  fetch spec always wins" philosophy (rejected relaxing that rule / rejected a runtime
+  is-property-loaded auto-skip check as less deterministic). The same `(source, target)` pair can be
+  declared more than once in `package-info.java` via a named variant, e.g.
+  `@DtoMapping(source = CUser.class, target = User.class)` (base/full) plus
+  `@DtoMapping(source = CUser.class, target = User.class, name = "noFleets", exclude = "fleets")`
+  (variant). Both variants are generated into the **same** mapper class (one class per target, not one
+  per variant) and share a single private `build(source, context, boolean includeXxx, ...)` method
+  containing the common field population written once; each excluded nested path becomes a `boolean
+  includeXxx` parameter of that shared method rather than a precomputed value, so `build()` still
+  evaluates every property - included or excluded - inline, at its own declared field position (a
+  `includeFleets ? fleetsMapper.mapList(...) : List.of()` ternary in place, not hoisted out as a
+  pre-evaluated call argument). This preserves the DTO's declared property order as the true evaluation
+  order regardless of which properties a variant happens to exclude. The base `map()` passes `true` for
+  every flag; each named variant (exposed as a same-named accessor, e.g. `noFleets()`, returning a single
+  shared/cached instance of its own small `DtoMapper<SOURCE, TARGET>`-implementing inner class - not
+  reconstructed per call) passes `false` for the paths it excludes and omits that path from its own
+  `fetchGroup`. Selected via a new `query.mapTo(Class<D> dtoType, DtoMapper<T, D> mapper)` overload
+  taking an already-resolved mapper instance directly (e.g. `query.mapTo(User.class,
+  userMapper.noFleets())`) - no string-based variant lookup, and no changes needed to
+  `DtoMapperRegister`/`DtoMapperManager`.
+  *Inspiration: `UserService`/`User` (central-access).*
+  *Status: implemented.*
+
+### H. Record entity sources
+
+- **Record-style (bare/fluent) accessors on the source (entity) side**
+  Ebean supports entity beans declared as Java `record`s (e.g. `public record CourseRecordEntity(@Id long id,
+  String name, String notes) {}` - see `test-java16`), whose only accessor shape is the bare component name
+  (`active()`, `name()`, `id()`) - never `getXxx()`/`isXxx()`. This bare-accessor convention isn't limited to
+  an actual `record` type though - an ordinary class can just as easily expose bare/fluent-style accessors
+  with no `get`/`is` prefix at all. The generator resolves the real accessor for each source type (the direct
+  source, or an intermediate `@DtoPath`/`@DtoRef` association type) by checking which shape actually exists as
+  a method, in order: (1) `isXxx()` returning `boolean` (JavaBean boolean convention), (2) `getXxx()` (JavaBean
+  convention), (3) the bare `propertyName()` itself - falling back to a guessed `getXxx()` only if none of the
+  three are found. Resolution is entirely name/existence-based (no dependency on whether the type is actually
+  a `record`). The Ebean bean-property name used in generated `FetchGroup.select(...)`/`.fetch(...)` calls is
+  tracked directly from the original property/segment name (not reverse-parsed from the resolved accessor's
+  method name), so it's correct regardless of which of the three accessor shapes was used.
+  *Inspiration: Ebean's own record-entity support (`test-java16`); user-reported gap during review.*
+  *Status: implemented.*
+
+## Rejected Requirements
+
+These were considered and explicitly rejected as out of scope:
+
+- **DTO as interface / dynamic proxy views** — Blaze `@EntityView` defines views as interfaces backed by
+  runtime proxies. This conflicts with Ebean's preference for plain, framework-unattached DTO classes.
+- **Updatable or creatable entity views (persist through DTO)** — Blaze's `@UpdatableEntityView` /
+  `@CreatableEntityView` cascade persist/update through the view. This would duplicate Ebean's existing
+  entity persistence model and introduce a second, ambiguous dirty-checking/cascade model.
+- **New predicate/filter DSL for subview collections** — Blaze allows filter expressions directly in
+  `@Mapping` (e.g. filtering a collection by an attribute value). Ebean already has typed query bean
+  predicates and `.filterMany()` for filtering child collections in queries; no new embedded filter
+  expression language is needed on the DTO itself.
+
+## References
+
+- Issue: https://github.com/ebean-orm/ebean/issues/2540
+- PR #2626: `InterceptReadOnly` / `InterceptReadWrite` split enabling the unmodifiable entity graph fast path
+- Ebean docs: https://ebean.io/docs/query/option#unmodifiable
+- QueryDSL: `@QueryProjection` (constructor-based, compile-time-checked projections)
+- Blaze-Persistence Entity Views: https://persistence.blazebit.com/documentation/1.6/entity-view/manual/en_US/

docs/guides/AGENTS.md

@@ -14,6 +14,7 @@ Key guides (fetch and follow when performing the relevant task):
 - Migrate to `Database.builder()`: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/migrating-to-database-builder.md
 - Migrate JSON APIs from Jackson core to avaje-json-core: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/migrating-json-jackson-core-to-avaje-json-core.md
 - Write queries with query beans: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/writing-ebean-query-beans.md
+- Mapping entity graphs to DTOs (`mapTo`): https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/mapping-entity-graphs-to-dtos.md
 - Derived / formula properties (`@Formula`, `@Formula2`): https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/derived-formula-properties.md
 - Persisting and transactions: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/persisting-and-transactions-with-ebean.md
 - Query metrics and naming: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/ebean-query-metrics.md

docs/guides/README.md

@@ -47,6 +47,7 @@ existing Maven project. Complete the steps in order.
 | Guide | Description |
 |-------|-------------|
 | [Write Ebean queries with query beans](writing-ebean-query-beans.md) | Step-by-step guidance for AI agents to write type-safe Ebean queries; choose the right terminal method; tune `select()` / `fetch()` / `fetchQuery()`; and project to DTOs when entity beans are not the right output |
+| [Mapping entity graphs to DTOs (`mapTo`)](mapping-entity-graphs-to-dtos.md) | Map a nested entity graph query result to a nested DTO graph via `query.mapTo(Dto.class)`; `@DtoPath`/`@DtoRef` for renamed/flattened/id-only properties; identity-aware de-dup via `DtoMapContext`; computed/aggregate DTO values via `@Entity @View` + `@Formula2`/`@Sum`/`@Aggregation`; comparison with the flat `asDto()` pipeline |
 | [Immutable bean cache for read-only references](immutable-bean-cache.md) | Use `ImmutableBeanCache` and `ImmutableBeanCaches.loading(...)` to resolve assoc-one references in read-only/unmodifiable queries, including secondary `fetchQuery`/`fetchLazy` loads |
 | [Using `RawSql` with Ebean](using-rawsql-with-ebean.md) | Choose between `RawSqlBuilder.parse()`, `unparsed()`, and `withPlaceholders()`; the `${where}`/`${andWhere}`/`${having}`/`${andHaving}` placeholder reference for CTEs, window functions, and subqueries; column mapping; and using `RawSql` with query beans |
 
@@ -153,6 +154,7 @@ Key guides (fetch and follow these when performing the relevant task):
 - Database configuration: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/add-ebean-postgres-database-config.md
 - Migrate to `Database.builder()`: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/migrating-to-database-builder.md
 - Write queries with query beans: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/writing-ebean-query-beans.md
+- Mapping entity graphs to DTOs (`mapTo`): https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/mapping-entity-graphs-to-dtos.md
 - Immutable bean cache for read-only references: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/immutable-bean-cache.md
 - Ebean OpenTelemetry tracing: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/add-ebean-opentelemetry.md
 - Query metrics and naming: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/ebean-query-metrics.md
@@ -182,6 +184,7 @@ Key guides (fetch and follow these when performing the relevant task):
 - Database configuration: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/add-ebean-postgres-database-config.md
 - Migrate to `Database.builder()`: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/migrating-to-database-builder.md
 - Write queries with query beans: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/writing-ebean-query-beans.md
+- Mapping entity graphs to DTOs (`mapTo`): https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/mapping-entity-graphs-to-dtos.md
 - Persisting and transactions: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/persisting-and-transactions-with-ebean.md
 - Test container setup: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/add-ebean-postgres-test-container.md
 - DB migration generation: https://raw.githubusercontent.com/ebean-orm/ebean/HEAD/docs/guides/add-ebean-db-migration-generation.md

docs/guides/mapping-entity-graphs-to-dtos.md

@@ -0,0 +1,785 @@
+# Guide: Mapping entity graphs to DTOs — `query.mapTo(Dto.class)`
+
+## Purpose
+
+`query.mapTo(SomeDto.class)` maps an entity query result to a **nested DTO graph** —
+DTO fields can themselves be DTOs (`ToOne`) or `List<Dto>`/`Set<Dto>` (`ToMany`), not
+just flat scalar columns. Ebean generates the mapper (reflection-free), automatically
+derives the query's `select()`/`fetch()` spec from the target DTO's declared shape, and
+forces `setUnmodifiable(true)` so any property the mapper needs but wasn't fetched fails
+fast with `LazyInitialisationException` instead of silently lazy loading.
+
+This is distinct from the existing flat `asDto(Dto.class)` — see
+[Quick comparison](#quick-comparison-mapto-vs-asdto-vs-plain-entity-query) below.
+
+```java
+Optional<CustomerDto> dto = new QCustomer()
+  .id.eq(customerId)
+  .mapTo(CustomerDto.class)
+  .findOneOrEmpty();
+```
+
+```java
+List<CustomerDto> dtos = DB.find(Customer.class)
+  .where().eq("status", Status.ACTIVE)
+  .mapTo(CustomerDto.class)   // no .select()/.fetch() needed - derived from CustomerDto's shape
+  .findList();
+```
+
+---
+
+## Quick comparison: `mapTo()` vs `asDto()` vs plain entity query
+
+| | `mapTo(Dto.class)` | `asDto(Dto.class)` | Plain entity query |
+|---|---|---|---|
+| Shape | Nested DTO **graph** (ToOne/ToMany) | Flat, single-row DTO | Entity graph |
+| Fetch spec | Auto-derived from the DTO's declared shape | Whatever `select()`/SQL you write | Whatever `select()`/`fetch()` you write |
+| Mismatch caught | At compile time (unregistered pair fails fast at first use; codegen fails fast on structural problems) | At runtime (reflection-based constructor/setter matching) | N/A (real entity properties) |
+| Identity/de-dup | Yes - repeated source instances map to the same DTO instance (`DtoMapContext`) | N/A (one row in, one DTO out) | Yes (entity/persistence-context identity) |
+| Backing pipeline | Executes the entity ORM query, `setUnmodifiable(true)`, maps the resulting graph | Executes SQL directly against a flat `ResultSet` | Executes the entity ORM query |
+| Best for | API/read-model responses that mirror a **nested** entity shape | Flat summary rows, reports, native/vendor SQL | Data you intend to mutate and save back |
+
+See also [writing-ebean-query-beans.md](writing-ebean-query-beans.md) (Step 8/9) for
+`asDto()` and the general query-shape decision guide.
+
+---
+
+## Basic usage
+
+### 1. Declare a plain DTO
+
+DTOs are plain classes with **no framework attachment** — no annotations required for
+the common case (properties matched to the source entity by name):
+
+```java
+public class CustomerDto {
+  private final Long id;
+  private final String name;
+  private final AddressDto billingAddress;   // nested ToOne
+  private final List<ContactDto> contacts;   // nested ToMany
+
+  public CustomerDto(Long id, String name, AddressDto billingAddress, List<ContactDto> contacts) {
+    this.id = id;
+    this.name = name;
+    this.billingAddress = billingAddress;
+    this.contacts = contacts;
+  }
+
+  public Long getId() { return id; }
+  public String getName() { return name; }
+  public AddressDto getBillingAddress() { return billingAddress; }
+  public List<ContactDto> getContacts() { return contacts; }
+}
+```
+
+A constructor whose parameters match (by name) a source entity/DTO property is used
+for mapping — same shape convention as the existing `DtoQuery`. Getters are used to
+read the source's properties — a bare/fluent accessor like `active()` is resolved
+automatically too, not just `getActive()`/`isActive()` (useful both for Ebean's own
+record entity beans and for ordinary classes that just expose bare-name accessors).
+
+### 2. Register the (source, target) pair
+
+Declare each entity → DTO pair with `@DtoMapping` on a `package-info.java` (a neutral
+holder — see [Why `package-info.java`?](#why-package-infojava)):
+
+```java
+@DtoMapping(source = Customer.class, target = CustomerDto.class)
+@DtoMapping(source = Address.class, target = AddressDto.class)
+@DtoMapping(source = Contact.class, target = ContactDto.class)
+package org.example.dto;
+
+import io.ebean.annotation.DtoMapping;
+```
+
+This triggers `querybean-generator` (the existing annotation processor) to generate a
+`CustomerDtoMapper implements DtoMapper<Customer, CustomerDto>` for each pair — no new
+Maven/Gradle setup beyond what query beans already require.
+
+### 3. Query with `mapTo(...)`
+
+```java
+List<CustomerDto> dtos = DB.find(Customer.class)
+  .where().eq("status", Status.ACTIVE)
+  .mapTo(CustomerDto.class)
+  .findList();
+
+CustomerDto one = new QCustomer().id.eq(id).mapTo(CustomerDto.class).findOne();
+
+Optional<CustomerDto> maybe = new QCustomer().id.eq(id).mapTo(CustomerDto.class).findOneOrEmpty();
+```
+
+`mapTo(...)` works the same from a query bean (`QCustomer`) or a plain `DB.find(...)`/
+`ExpressionList` query.
+
+### Paging - `findPagedList()`
+
+`findPagedList()` mirrors `Query#findPagedList()` — the underlying entity query is paged
+as normal and each page's result is mapped to the target DTO list:
+
+```java
+PagedList<CustomerDto> paged = DB.find(Customer.class)
+  .where().eq("status", Status.ACTIVE)
+  .orderBy().asc("name")
+  .setFirstRow(0)
+  .setMaxRows(50)
+  .mapTo(CustomerDto.class)
+  .findPagedList();
+
+int totalRowCount = paged.getTotalCount();      // page metadata - unaffected by DTO mapping
+List<CustomerDto> page1 = paged.getList();       // mapped DTOs for this page
+```
+
+Page metadata (`getTotalCount()`, `getTotalPageCount()`, `hasNext()`, `hasPrev()`,
+`loadCount()`, ...) reflects the underlying entity query directly; only `getList()`
+is mapped (once, cached) to the DTO type.
+
+### An unregistered pair fails fast
+
+If `(Customer.class, SomeDto.class)` was never declared via `@DtoMapping`, the first
+`mapTo(SomeDto.class)` call throws immediately:
+
+```
+PersistenceException: No DtoMapper registered mapping Customer -> SomeDto
+  - check @DtoMapping(source = Customer.class, target = SomeDto.class) is declared
+    on a package-info.java processed by querybean-generator
+```
+
+---
+
+## Auto-derived fetch spec
+
+You never write `.select()`/`.fetch()` for a `mapTo(...)` query — the generated mapper
+exposes a `fetchGroup()` built directly from the DTO's declared shape, and `mapTo(...)`
+applies it automatically:
+
+```java
+public CustomerDtoMapper() {
+  this(new AddressDtoMapper(), new ContactDtoMapper());
+}
+
+public CustomerDtoMapper(DtoMapper<Address, AddressDto> billingAddressMapper,
+                          DtoMapper<Contact, ContactDto> contactsMapper) {
+  this.fetchGroup = FetchGroup.of(Customer.class)
+    .select("id,name")
+    .fetch("billingAddress", billingAddressMapper.fetchGroup())
+    .fetch("contacts", contactsMapper.fetchGroup())
+    .build();
+}
+```
+
+Each nested DTO gets its own generated mapper (mirroring MapStruct's per-type mapper
+generation), wired together via constructor injection — mappers are stateless and
+substitutable, not static singletons. Mapper instances are constructed once, in
+dependency order, and reused — see [DtoMapperManager](#one-mapper-instance-per-pair)
+below.
+
+---
+
+## Nested collections and identity-aware de-duplication
+
+When the same source entity instance is reachable via more than one path in the graph
+(e.g. two `Contact`s sharing the same `Customer`, or the same `Address` referenced from
+two paths), the mapper reuses the **same** target DTO instance rather than creating
+duplicate-but-equal copies — mirroring the identity semantics the entity graph already
+has:
+
+```java
+List<CustomerDto> dtos = DB.find(Customer.class).mapTo(CustomerDto.class).findList();
+
+CustomerDto customer = dtos.get(0);
+// both contacts share the exact same customer.billingAddress AddressDto instance
+assertThat(customer.getContacts().get(0).getCustomer())
+  .isSameAs(customer.getContacts().get(1).getCustomer());
+```
+
+This is done via a `DtoMapContext` threaded through every nested `map(...)` call within
+one top-level `mapList(...)`/`findList()` invocation. The generated code only pays for
+this when it can actually matter — a DTO that's never nested under another DTO skips
+`DtoMapContext` entirely (there's nothing else in scope to de-duplicate against):
+
+```java
+// AddressDto is nested under CustomerDto (reachable via multiple contacts) - dedup needed
+// dedup using DtoMapContext, same Address instance can be reached via more than one path in the graph
+return context.computeIfAbsent(AddressDto.class, source, s -> new AddressDto(...));
+
+// ContactSummaryDto is only ever mapped as a top-level query result - no dedup possible
+// skip DtoMapContext, only ever a top-level mapping
+return new ContactSummaryDto(source.getId(), source.getFullName());
+
+// CustomerDto has nested mappers (billingAddress, contacts) but is never itself nested
+// DtoMapContext for nested mappers only
+return new CustomerDto(source.getId(), source.getName(), ...);
+```
+
+The generated comment tells you at a glance which of the three cases applies — useful
+when debugging why a `DtoMapContext` is (or isn't) in the generated code for a
+particular mapper.
+
+---
+
+## Using generated mappers directly (outside `query.mapTo()`)
+
+Every generated `XxxDtoMapper` is a plain public class — you don't need `ServiceLoader`,
+a registry, or a `Database` just to construct or call one directly (though
+`DtoMapperManager`, below, is available if you want a shared, DI-friendly lookup). It
+always has a public no-arg constructor (delegating to defaults for any nested mappers/
+`@DtoConvert` converters) plus an explicit constructor taking those dependencies directly,
+and implements `DtoMapper<SOURCE, TARGET>`'s `map(...)`/`mapList(...)`:
+
+```java
+CustomerDtoMapper mapper = new CustomerDtoMapper();
+CustomerDto dto = mapper.map(customer);       // any Customer you already have on hand
+List<CustomerDto> dtos = mapper.mapList(customers);
+```
+
+This works on **any** entity graph, not just one that just came out of a `mapTo(...)`
+query — e.g. entities you loaded with a plain `.fetch(...)` query, entities you just
+`.save()`d, or entities built by hand in a test. The only requirement is that whatever the
+mapper reads (via plain getters) is actually populated — there's no lazy-loading fallback.
+
+### Testing the mapping in isolation
+
+Because mappers are plain, constructor-injected classes, you can unit test the mapping
+logic itself — independent of `query.mapTo()`, the DTO-pair registry, and (for
+`@DtoConvert` instance-dispatch converters) `DtoConverterManager` — by passing a test
+double straight into the explicit constructor:
+
+```java
+SecretCipher upperCasingTestCipher = String::toUpperCase;
+ContactConversionDto dto = new ContactConversionDtoMapper(upperCasingTestCipher).map(contact);
+
+assertThat(dto.getSecretCode()).isEqualTo("SHH");
+```
+
+No `DtoConverterManager.put(...)` registration needed for this kind of test — the real
+production wiring (`DtoConverterManager.get(SecretCipher.class)`) only happens in the
+generated no-arg constructor, which the explicit-constructor call above bypasses entirely.
+See `TestCustomerDtoGraphMapping` (mapper called directly against a manually queried
+graph) and `TestMapperManualUsage` (mapper called directly against hand-built/just-saved
+entities, plus the converter test-double case above) in `tests/test-dto-mapping`.
+
+### `DtoMapperManager` — resolving a generated mapper for dependency injection
+
+`new CustomerDtoMapper()` is enough for a single mapper, but if your application wants a
+single shared instance of *every* generated mapper (mirroring how `query.mapTo()` resolves
+them internally) - e.g. to wire one up for constructor injection into a service, replacing
+a hand-written mapper class - use `io.ebean.DtoMapperManager`:
+
+```java
+DtoMapperManager manager = new DtoMapperManager();   // ServiceLoader discovery only - no Database needed
+CustomerDtoMapper mapper = manager.get(CustomerDtoMapper.class);
+```
+
+`DtoMapperManager` has no dependency on `Database` at all - its constructor only does
+`ServiceLoader.load(DtoMapperRegister.class)` - so it can be constructed independently,
+before (or entirely without) a `Database`, e.g. as a bean in an avaje-inject (or any DI
+framework's) dependency graph:
+
+```java
+@Factory
+class DtoMapperFactory {
+
+  @Bean
+  DtoMapperManager dtoMapperManager() {
+    return new DtoMapperManager();
+  }
+
+  @Bean
+  CustomerDtoMapper customerDtoMapper(DtoMapperManager manager) {
+    return manager.get(CustomerDtoMapper.class);
+  }
+}
+```
+
+If you also want `query.mapTo(...)` to use that *exact same* manager instance (so there's
+only ever one instance of each generated mapper, whichever path resolves it), register it
+via `DatabaseBuilder.putServiceObject` before building the `Database` - this is the same
+`putServiceObject`/`getServiceObject` mechanism already used for things like
+`AutoMigrationRunner`:
+
+```java
+DtoMapperManager sharedManager = new DtoMapperManager();
+
+Database db = Database.builder()
+  .putServiceObject(DtoMapperManager.class, sharedManager)
+  .build();
+
+// query.mapTo(...) against `db` now resolves mappers via `sharedManager`
+```
+
+If nothing is registered via `putServiceObject`, the `Database` builds its own default
+`DtoMapperManager` instance instead - registering one is entirely optional. A standalone
+`DtoMapperManager()` construction bypasses the `DatabaseConfigProvider` hook (that hook is
+specifically about `Database` startup ordering), so if any of your mappers need a
+`@DtoConvert` instance-dispatch converter, register it via `DtoConverterManager.put(...)`
+yourself first, exactly as you would before building a `Database`. See
+`TestDtoMapperManager` and `TestDtoMapperManagerSharing` in `tests/test-dto-mapping`.
+
+### Recipe: adding extra caller-supplied fields after mapping
+
+Sometimes a target DTO needs a field that isn't sourced from the entity graph at all - e.g.
+populated from a separate query or business rule, only when a caller-supplied flag is set.
+Rather than the generator supporting partial/builder-based mapping directly, if your DTO is
+a record with a "seed from instance" builder (e.g. via `avaje-recordbuilder`'s
+`@RecordBuilder`, which generates `Target.builder(existingInstance)`), just map the
+graph-sourced fields as usual and layer the extra field on afterwards:
+
+```java
+Driver base = mapper.map(cDriver);
+Driver full = DriverBuilder.builder(base).fleets(fleets).build();
+```
+
+No generator changes needed - the mapped instance is simply the seed for the builder.
+
+---
+
+## Large targets: builder-based construction and named variants
+
+Two features aimed at large, builder-shaped target DTOs (typically OpenAPI-generated records
+with a generated builder), where a positional constructor call is unwieldy and a single query
+needs to populate the target in more than one shape.
+
+### Builder-based construction (`builder = AUTO | ALWAYS | NEVER`)
+
+If the target has a static no-arg `Target.builder()` factory returning a type with a fluent
+(returns-itself) setter per property plus a `build()` method - the shape
+`avaje-recordbuilder`'s `@RecordBuilder` generates - the generated mapper can construct the
+target via `Target.builder().prop(x)....build()` instead of `new Target(a, b, c, ...)`:
+
+```java
+public record User(Long id, String name, String email, /* ... 21 more fields */) {
+
+  public static UserBuilder builder() {
+    return UserBuilder.builder();
+  }
+}
+```
+
+```java
+@DtoMapping(source = CUser.class, target = User.class)
+package org.example.dto;
+```
+
+By default (`builder = AUTO`), the generator auto-detects a matching builder and uses it only
+once the target has more than 5 properties, falling back to a positional constructor for
+smaller DTOs. Override explicitly either direction:
+
+```java
+@DtoMapping(source = CUser.class, target = User.class, builder = DtoMapping.Builder.ALWAYS)
+```
+
+`builder = ALWAYS` is a codegen-time error if no matching builder shape is found; `builder =
+NEVER` always uses a positional constructor even if a builder is detected. This applies
+regardless of whether the target is hand-authored or foreign/generated - `@DtoMapping` is
+already declared externally via `package-info.java`, so no annotation on the target itself is
+needed either way.
+
+### Named variants excluding nested paths (`name=`, `exclude=`)
+
+The same `(source, target)` pair can be registered more than once - one base mapping (leaving
+`name()` empty) plus any number of named variants, each excluding one or more nested
+ToOne/ToMany properties:
+
+```java
+@DtoMapping(source = CUser.class, target = User.class)
+@DtoMapping(source = CUser.class, target = User.class, name = "noFleets", exclude = "fleets")
+package org.example.dto;
+```
+
+Both variants are generated into the **same** mapper class (one class per target, not one per
+variant) - the generated `noFleets()` accessor returns a single shared/cached `DtoMapper<CUser,
+User>` view (not reconstructed per call), omitting `fleets` from both its mapped output (`null`
+for a ToOne, `List.of()` for a ToMany) and its own `fetchGroup()`. Each excluded property is still
+evaluated inline at its own declared field position internally (guarded by a boolean flag) - a
+variant's exclusions never change the evaluation order of the DTO's other properties. Select it
+with the `query.mapTo(Class, DtoMapper)` overload, which takes an already-resolved mapper instance
+directly - no string-based lookup:
+
+```java
+UserMapper userMapper = new UserMapper();
+
+// full shape, with fleets fetched/mapped
+List<User> withFleets = DB.find(CUser.class)
+  .mapTo(User.class, userMapper) // or plain .mapTo(User.class)
+  .findList();
+
+// bulk listing shape - fleets excluded from both the fetch spec and the output
+List<User> noFleets = DB.find(CUser.class)
+  .mapTo(User.class, userMapper.noFleets())
+  .findList();
+```
+
+Only nested ToOne/ToMany properties can be excluded - a scalar or `@DtoRef` property can't be,
+since there's no type-safe "absent" value for an arbitrary scalar type. Named variants are
+scoped to independent, top-level query results only - unlike the base mapping, they don't
+participate in `DtoMapContext` identity de-duplication when nested elsewhere in a graph, since a
+variant is never intended to be nested inside another DTO's mapping.
+
+---
+
+## `@DtoPath` — renamed or flattened properties
+
+By default a DTO property is matched to the source entity property (or nested DTO
+mapper) of the **same name**. `@DtoPath` overrides that, allowing a DTO property to be
+renamed and/or flattened from a nested path using dot-notation:
+
+```java
+public class ContactDto {
+  private final long id;
+  private final String firstName;
+  private final String lastName;
+
+  @DtoPath("customer.billingAddress.city")
+  private final String customerCity;   // flattened, 2 hops through customer
+
+  // constructor / getters ...
+}
+```
+
+The generated mapper reads the path with a null-guard at each hop and adds the
+necessary joins to the fetch spec automatically:
+
+```java
+(s.getCustomer() == null ? null
+  : (s.getCustomer().getBillingAddress() == null ? null
+      : s.getCustomer().getBillingAddress().getCity()))
+```
+
+`@DtoPath` is purely a compile-time/codegen-time hint — the DTO class itself carries no
+runtime dependency on the annotation.
+
+### Fetch-path collisions are a compile-time error
+
+A `@DtoPath` whose fetch path is identical to a nested `ToOne`/`ToMany` property's own
+fetch path on the *same* DTO (e.g. a nested `customer` field alongside
+`@DtoPath("customer.name")` — both resolve to fetch path `"customer"`) fails the build
+with a clear error, rather than silently discarding one side's fetched properties:
+
+```
+error: @DtoPath property 'customerName' on FooDto resolves to fetch path 'customer',
+  which collides with the nested mapping already using that same fetch path - Ebean's
+  fetch spec can only carry one set of properties per path, so one silently discards
+  the other. Move 'customerName' onto the nested DTO type instead, or choose a
+  @DtoPath that reaches into a different, non-colliding path.
+```
+
+Fix it either way it suggests: move the property onto the nested DTO type, or choose a
+`@DtoPath` that reaches a different path (as `customerCity` above does deliberately,
+using a 3-segment path through `customer.billingAddress` rather than colliding with a
+plain `customer` nested field).
+
+---
+
+## `@DtoRef` — id-only back-references (breaking cycles)
+
+The DTO graph derived from a set of DTO types must form a DAG — codegen fails if it
+doesn't. `@DtoRef` is the explicit escape hatch for an intentional back-reference, e.g.
+a `Contact` DTO referencing its parent `Customer` by id only, rather than re-embedding
+a full `CustomerDto` (which would recreate the `Customer → Contact → Customer` cycle):
+
+```java
+public class ContactDto {
+  private final long id;
+
+  @DtoRef
+  private final Long customerId;   // id-only, no nested CustomerDto re-embedded
+
+  // constructor / getters ...
+}
+```
+
+The generated fetch spec adds the association to the **root** `select(...)` rather
+than a nested `.fetch(...)` — this reads the foreign-key column directly off the base
+table (no SQL join):
+
+```java
+this.fetchGroup = FetchGroup.of(ContactStats.class)
+  .select("customer,contactCount,engagementScore")   // "customer" -> FK column, no join
+  .build();
+```
+
+```java
+(source.getCustomer() == null ? null : source.getCustomer().getId())
+```
+
+If the same association is *also* independently nested-fetched elsewhere on the DTO
+(e.g. `ContactDto` has both a nested `customer` field **and** `@DtoRef Long
+customerId`), the generator recognizes the association is already covered and doesn't
+add a redundant/duplicate select — no join is added twice.
+
+---
+
+## `@DtoConvert` — custom property conversion
+
+Some properties need more than a plain getter copy — a scalar coercion (`short` to
+`boolean`), an enum-to-`String` mapping, or a conversion needing a real dependency (e.g.
+decrypting a value with a cipher). `@DtoConvert(value = ConverterType.class, method =
+"name")` covers both, combinable with `@DtoPath` when the source value also needs a
+path/rename override:
+
+```java
+public class ContactDto {
+  @DtoPath("status")
+  @DtoConvert(value = ContactConversions.class, method = "toActive")
+  private final boolean active;             // Contact.status (Short) -> boolean
+
+  @DtoConvert(value = SecretCipher.class, method = "decode")
+  private final String secretCode;          // decrypted via a registered SecretCipher
+
+  // constructor / getters ...
+}
+```
+
+The generator resolves the referenced method at codegen time and dispatches one of two
+ways, purely based on whether it's `static`:
+
+- **Static method** — inlined as a direct static call
+  (`ContactConversions.toActive(source.getStatus())`). No registration needed at all —
+  use this for common, reusable, dependency-free coercions.
+- **Instance method** — the generated mapper resolves one shared instance via
+  `DtoConverterManager.get(SecretCipher.class)`, wired as a constructor
+  parameter/field (the same shape as nested-mapper constructor injection), then calls
+  `secretCipher.decode(source.getSecretCode())`. Use this when the conversion needs a
+  real dependency.
+
+### Registering an instance-dispatch converter
+
+`DtoConverterManager` is a small, deliberately-scoped static put/get bridge — register
+an already-constructed converter instance (e.g. built by your DI container) **before**
+building the `Database`:
+
+```java
+AES256Cipher cipher = ...;                                    // already DI-constructed
+DtoConverterManager.put(SecretCipher.class, cipher::decrypt); // or a small adapter class
+
+Database db = DatabaseFactory.create(...); // generated mappers resolve converters from here
+```
+
+If nothing is registered for a required type, `DtoConverterManager.get(...)` throws a
+`PersistenceException` immediately — this happens as an eager field initializer on the
+generated `EbeanDtoMapperRegister`, so a missing registration fails fast at `Database`
+build time, not lazily on first `mapTo(...)` call.
+
+> **Testing tip:** since `EbeanDtoMapperRegister`'s mapper fields are all constructed
+> together when the `Database` starts, register converters via a `DatabaseConfigProvider`
+> (a `ServiceLoader` hook that runs before the `Database` is built) rather than a test
+> `@BeforeAll`, so registration always happens before *any* test triggers startup —
+> regardless of which test class runs first.
+
+## `@DtoMixin` — overlaying annotations onto a DTO you can't edit
+
+Some DTOs are generated elsewhere (e.g. from an OpenAPI spec, regenerated on every
+build) and can't be annotated directly. `@DtoMixin(Target.class)` overlays
+`@DtoPath`/`@DtoRef`/`@DtoConvert` from a separate companion type instead — directly
+mirroring avaje-jsonb's `@Json.MixIn` mechanism. Declare a companion interface (or
+class) whose method names match the target DTO's property names:
+
+```java
+// ContactMixinDto itself carries no Ebean annotations at all
+public class ContactMixinDto {
+  public ContactMixinDto(long id, String firstName, boolean active, String secretCode) { ... }
+  // getters ...
+}
+
+@DtoMixin(ContactMixinDto.class)
+interface ContactMixinDtoMixin {
+
+  @DtoPath("status")
+  @DtoConvert(value = ContactConversions.class, method = "toActive")
+  boolean active();
+
+  @DtoConvert(value = SecretCipher.class, method = "decode")
+  String secretCode();
+}
+```
+
+The processor matches each mixin method to the target's property by name and applies
+whichever annotations are present as if they were declared on the target field itself.
+The mixin type is never instantiated and carries no runtime footprint — it's purely a
+compile-time/codegen-time hint.
+
+---
+
+## Computed / aggregate properties via `@Entity @View`
+
+There's no dedicated "formula on DTO" annotation (a narrower `@Formula2`-on-DTO
+variant was explored and rejected — see
+[dto-mapping-design.md](../dto-mapping-design.md) for the reasoning). Instead, model
+the computed value as its own read-only entity using `@View`, then map that entity to a
+plain DTO with the same `@DtoMapping` machinery described above. `@View(name = "...")`
+here just points a second entity at an **existing** table — it does not create a new
+database view or table.
+
+### Worked example — computed column (`@Formula2`)
+
+```java
+@Entity
+@View(name = "contact")   // reads the existing 'contact' table, no new DDL
+public class ContactSummary {
+  @Id
+  private Long id;
+  private String firstName;
+  private String lastName;
+
+  @Formula2("concat(firstName, ' ', lastName)")
+  private String fullName;
+
+  // getters ...
+}
+```
+
+```java
+public class ContactSummaryDto {
+  private final Long id;
+  private final String fullName;
+  // constructor / getters ...
+}
+```
+
+```java
+@DtoMapping(source = ContactSummary.class, target = ContactSummaryDto.class)
+```
+
+```java
+List<ContactSummaryDto> summaries = DB.find(ContactSummary.class)
+  .mapTo(ContactSummaryDto.class)
+  .findList();
+```
+
+### Worked example — group-by aggregation (`@Sum`/`@Aggregation`)
+
+The same `@View`-on-base-table pattern applies to Ebean's `@Sum`/`@Aggregation`
+group-by formulas — the Blaze-Persistence parallel is an `@EntityView` with
+`@Mapping("SIZE(...)")`/`@Mapping("SUM(...)")` correlated mappings:
+
+```java
+@Entity
+@View(name = "contact")
+public class ContactStats {
+  @Id
+  private Long id;              // required so @Aggregation("count(id)") has something to
+                                 // count; deliberately never selected/mapped - selecting it
+                                 // would defeat the aggregation (one row per contact
+                                 // instead of one row per customer)
+  @ManyToOne
+  private Customer customer;
+
+  @Aggregation("count(id)")
+  private Long contactCount;
+
+  @Sum
+  private Integer engagementScore;
+
+  // getters ...
+}
+```
+
+```java
+public class ContactStatsDto {
+  @DtoRef
+  private final Long customerId;   // also the implicit GROUP BY key
+  private final Long contactCount;
+  private final Integer engagementScore;
+  // constructor / getters ...
+}
+```
+
+Because `customerId` uses `@DtoRef`, the generated fetch spec is
+`select("customer,contactCount,engagementScore")` with **no join** — the query groups
+by the FK column directly:
+
+```sql
+select t0.customer_id, count(t0.id), sum(t0.engagement_score)
+from contact t0
+group by t0.customer_id
+```
+
+---
+
+## Performance notes
+
+### Fail-fast, no accidental lazy loading
+
+`mapTo(...)` forces `query.setUnmodifiable(true)` under the hood. If the mapper ever
+needs a property that wasn't fetched, it throws `LazyInitialisationException`
+immediately rather than silently issuing an extra query per row or returning `null`.
+`InterceptReadOnly` (the unmodifiable-graph bean state) is also cheap — a `boolean[]
+loaded` flag array plus a `frozen` flag, not a full second copy of bean state.
+
+### One mapper instance per pair
+
+Generated mappers are constructed once (in dependency order — a mapper with nested
+mappers takes them as constructor params) and reused across every `mapTo(...)` call for
+that pair, resolved and cached by `DtoMapperManager` keyed on `(sourceType, dtoType)`.
+
+### `DtoMapContext` overhead only where it earns its keep
+
+As shown above, the generator only involves `DtoMapContext` for mappers that can
+actually be reached via more than one path in some graph (dedup) or that have nested
+mappers of their own (need to thread the context down); a DTO that's only ever a
+top-level query result skips it entirely.
+
+### Fetch strategy and pagination carry over unchanged
+
+Existing fetch-strategy control (`+query`/`+lazy`, `fetchQuery()`) and pagination
+(including keyset pagination and `findPagedList()`) work the same whether the query
+target is an entity graph or a `mapTo(...)` DTO graph — no special-casing needed.
+
+---
+
+## Which should I use?
+
+- **`mapTo(Dto.class)`** — the target is a **nested** shape (has its own ToOne/ToMany
+  DTO fields) that should mirror part of the entity graph; you want the fetch spec
+  derived automatically and verified to match the DTO's declared shape.
+- **`asDto(Dto.class)`** / `DB.findDto(...)` — the target is a **flat** row (report,
+  summary, native/vendor SQL); you're comfortable with runtime-checked column-to-bean
+  matching, or the SQL doesn't map cleanly to entity property paths at all.
+- **Plain entity query** — the caller needs a real, persistable, mutable entity — not a
+  read-only projection.
+
+---
+
+## Reference
+
+### Why `package-info.java`?
+
+`@DtoMapping` is declared on a package (`ElementType.PACKAGE`), not the DTO or the
+entity, because:
+- the DTO type is often owned/generated elsewhere (e.g. from an OpenAPI spec) and
+  shouldn't need to be annotated with an internal persistence/entity type;
+- one entity may be the source for several different DTOs (e.g. a summary vs. a detail
+  view), and the same entity/DTO pair may need registering from multiple consuming
+  modules.
+
+### Annotations at a glance
+
+| Annotation | Target | Purpose |
+|---|---|---|
+| `@DtoMapping(source=, target=)` | `package-info.java` | Registers an entity → DTO pair, triggers mapper generation |
+| `@DtoMapping(..., builder=)` | `package-info.java` | `AUTO` (default, threshold-based) / `ALWAYS` / `NEVER` - builder-chain vs positional constructor |
+| `@DtoMapping(..., name=, exclude=)` | `package-info.java` | Registers a named variant sharing the base mapping's generated class, excluding nested paths |
+| `@DtoPath("a.b.c")` | DTO field/getter | Renamed and/or flattened multi-hop property mapping |
+| `@DtoRef` | DTO field/getter | Id-only back-reference; breaks a cycle; root-selects the FK (no join) |
+| `@DtoConvert(value=, method=)` | DTO field/getter | Custom scalar conversion - static (no registration) or instance (via `DtoConverterManager`) dispatch |
+| `@DtoMixin(Target.class)` | Companion interface/class | Overlays `@DtoPath`/`@DtoRef`/`@DtoConvert` onto a DTO that can't be annotated directly |
+
+### Parallels with other tools
+
+If you're coming from another mapping library, here's the rough correspondence:
+
+| Ebean | MapStruct | Blaze-Persistence |
+|---|---|---|
+| Generated `DtoMapper` per (source, DTO) pair | Generated `@Mapper` implementation | `@EntityView` (interface + runtime proxy) |
+| `@DtoPath("a.b.c")` | `@Mapping(target = "x", source = "a.b.c")` | `@Mapping("a.b.c")` |
+| `@DtoRef` | `@Context`/manual cycle-breaking (no dedicated annotation) | Sub-view referencing an id-only projection |
+| `@DtoConvert(value=, method=)` | `@Mapping(qualifiedByName = "...")` / custom mapper methods | Custom converter/`@Mapping` expression |
+| `@DtoMixin(Target.class)` | N/A (annotate the `@Mapper` interface's abstract methods instead) | N/A |
+| `DtoMapContext` identity de-dup | Not built in (opt-in `@MappingTarget`/manual caching) | Built in (entity-view identity) |
+| `@Entity @View` + `@Formula2`/`@Sum`/`@Aggregation` for computed DTO values | N/A (MapStruct doesn't touch SQL) | `@Mapping("SIZE(...)")` / `@Mapping("SUM(...)")` correlated mappings |
+
+See [dto-mapping-design.md](../dto-mapping-design.md) for the full design rationale and
+[dto-mapping-requirements.md](../dto-mapping-requirements.md) for the accepted/rejected
+requirements this feature was scoped against (issue
+[#2540](https://github.com/ebean-orm/ebean/issues/2540)).

docs/guides/writing-ebean-query-beans.md

@@ -462,6 +462,11 @@ List<CustomerSummary> summaries = new QCustomer()
 - the result is not going to be updated and saved back as an entity
 - the query contains formulas or aggregation intended for a read model
 
+`asDto(...)` maps a **flat**, single-row result. If the target DTO itself needs nested
+DTO fields (ToOne/ToMany) mirroring part of the entity graph, use
+`mapTo(Dto.class)` instead — see
+[Mapping entity graphs to DTOs](mapping-entity-graphs-to-dtos.md).
+
 ---
 
 ## Step 9 - Only fall back to raw SQL when the ORM query is not a good fit

ebean-api/src/main/java/io/ebean/DtoConverterManager.java

@@ -0,0 +1,65 @@
+package io.ebean;
+
+import jakarta.persistence.PersistenceException;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Static bridge registering custom {@code @DtoConvert} converter instances so generated DTO
+ * mappers can reach them.
+ * <p>
+ * Generated mappers (see {@code query.mapTo(SomeDto.class)}) are wired via {@code ServiceLoader}
+ * as plain, no-arg-constructed, compile-time singletons (mirroring how entity/query-bean
+ * registration already works) - they have no way to reach a dependency-injection container, or
+ * any particular {@code Database} instance, at construction time. When a
+ * {@code @DtoConvert(value = ConverterType.class, method = "...")} property's converter is an
+ * <b>instance</b> method (as opposed to a {@code static} one, which is called directly with no
+ * registration needed at all), the generated mapper resolves it via {@link #get(Class)} - so the
+ * application must register an instance here, typically one already built by its own DI
+ * container, <b>before</b> building the {@code Database}:
+ * <pre>{@code
+ * AES256Cipher cipher = ...; // already DI-constructed
+ * DtoConverterManager.put(DriverConversions.class, new DriverConversionsImpl(cipher));
+ *
+ * Database db = DatabaseFactory.create(...); // generated mappers resolve converters from here
+ * }</pre>
+ * <p>
+ * This is a deliberate, narrowly-scoped exception to preferring dependency injection over static
+ * mutable state - it exists solely to bridge an already-DI-constructed singleton into
+ * {@code ServiceLoader}-discovered, no-arg-constructed generated code, which cannot otherwise
+ * reach a DI container or a specific {@code Database} instance. {@link #get(Class)} throws
+ * immediately if nothing was registered for the given type, so a missing/late registration fails
+ * fast at {@code Database} build time (a generated mapper's eager field initializer) rather than
+ * lazily on first use.
+ */
+public final class DtoConverterManager {
+
+  private static final Map<Class<?>, Object> converters = new ConcurrentHashMap<>();
+
+  private DtoConverterManager() {
+  }
+
+  /**
+   * Register a converter instance for the given type - must be called before the
+   * {@code Database} using it is built.
+   */
+  public static <T> void put(Class<T> type, T instance) {
+    converters.put(type, instance);
+  }
+
+  /**
+   * Return the registered converter instance for the given type.
+   *
+   * @throws PersistenceException if no instance was registered for {@code type}.
+   */
+  @SuppressWarnings("unchecked")
+  public static <T> T get(Class<T> type) {
+    T instance = (T) converters.get(type);
+    if (instance == null) {
+      throw new PersistenceException("No " + type.getName() + " registered - call "
+        + "DtoConverterManager.put(" + type.getSimpleName() + ".class, ...) before starting the Database");
+    }
+    return instance;
+  }
+}

ebean-api/src/main/java/io/ebean/DtoMapContext.java

@@ -0,0 +1,51 @@
+package io.ebean;
+
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+/**
+ * Identity-keyed cache of already-mapped source -> target instances, shared across one
+ * top-level {@link DtoMapper#mapList(java.util.List)} call (or an explicitly shared context).
+ * <p>
+ * Keyed by source object <b>identity</b> (an {@link IdentityHashMap}, not {@code equals()}/
+ * {@code hashCode()}) because the source is an Ebean entity graph, where repeated references to
+ * the same row within one query already resolve to the same Java object instance.
+ * <p>
+ * The identity map is partitioned <b>per target DTO type</b>. This matters because the same
+ * source instance can legitimately need to be mapped to more than one target type within a
+ * single graph - e.g. a top-level {@code CustomerDtoMapper} maps a {@code Customer} to a full
+ * {@code CustomerDto}, while a nested {@code ContactDtoMapper} maps the very same {@code Customer}
+ * instance (accessed via {@code contact.getCustomer()}) to a shallow {@code CustomerRefDto} to
+ * avoid a cycle. A single un-partitioned {@code IdentityHashMap<Object,Object>} would have the
+ * two mappers collide on the same source key and incorrectly hand back the other mapper's
+ * (wrong-typed) cached result. Partitioning by target type keeps each mapper's cache isolated
+ * while still sharing one context/instance per top-level mapping call.
+ * <p>
+ * Not thread-safe - a context is expected to be created per top-level mapping call and not
+ * shared across threads.
+ */
+public final class DtoMapContext {
+
+  private final Map<Class<?>, Map<Object, Object>> mappedByType = new HashMap<>();
+
+  /**
+   * Return the already-mapped target for the given source instance if present, otherwise map it
+   * via {@code mappingFunction}, register it, and return it.
+   *
+   * @param targetType the DTO type being produced - used to partition the identity cache so that
+   *     mapping the same source to different target types never collides.
+   */
+  @SuppressWarnings("unchecked")
+  public <S, T> T computeIfAbsent(Class<T> targetType, S source, Function<S, T> mappingFunction) {
+    Map<Object, Object> mapped = mappedByType.computeIfAbsent(targetType, t -> new IdentityHashMap<>());
+    T existing = (T) mapped.get(source);
+    if (existing != null) {
+      return existing;
+    }
+    T created = mappingFunction.apply(source);
+    mapped.put(source, created);
+    return created;
+  }
+}

ebean-api/src/main/java/io/ebean/DtoMapper.java

@@ -0,0 +1,76 @@
+package io.ebean;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Mapper interface implemented by generated (or hand-written) entity -> DTO graph mappers.
+ * <p>
+ * Used with nested entity-to-DTO graph mapping (see {@code query.mapTo(SomeDto.class)}) as
+ * distinct from the existing flat, single-row {@link DtoQuery} pipeline. Each entity/DTO type
+ * pair gets its own small, composable mapper implementation (mirroring MapStruct's per-type
+ * mapper generation) rather than one large mapper inlining every nested type. Nested mappers are
+ * wired together via constructor injection, not static singletons - this keeps mappers stateless,
+ * substitutable (e.g. for tests) and avoids global mutable state.
+ * <p>
+ * A {@link DtoMapContext} is threaded through every nested {@code map(...)} call within one
+ * top-level {@link #mapList(List)} invocation, so that repeated references to the same source
+ * entity instance (e.g. several {@code Contact}s sharing the same {@code Customer}) map to the
+ * <b>same</b> target DTO instance rather than creating duplicate-but-equal copies. This mirrors
+ * the identity semantics Ebean's own entity graph already has, and is what makes the resulting
+ * DTO graph "graph shaped" rather than "tree of copies shaped".
+ * <p>
+ * Implementations contain no reflection or {@code MethodHandles} - only direct getter calls and
+ * constructor invocation - so generated mappers are safe under GraalVM native-image with zero
+ * additional reachability metadata.
+ *
+ * @param <SOURCE> the source entity (or embeddable) type
+ * @param <TARGET> the target DTO type
+ */
+public interface DtoMapper<SOURCE, TARGET> {
+
+  /**
+   * Return the {@link FetchGroup} of exactly the source properties (and nested paths) needed to
+   * populate the target DTO graph - the select()/fetch() spec is derived from the DTO's declared
+   * shape rather than maintained separately by hand. Used by {@code query.mapTo(TARGET.class)}
+   * to automatically apply the correct fetch spec before the query is executed.
+   */
+  FetchGroup<SOURCE> fetchGroup();
+
+  /**
+   * Map a single source instance to its target DTO, reusing/registering the mapping in the
+   * given context so that repeated references to the same source instance de-duplicate to the
+   * same target instance. Must return {@code null} when given {@code null}.
+   */
+  TARGET map(SOURCE source, DtoMapContext context);
+
+  /**
+   * Map a single source instance using a fresh, one-off context. Convenience for mapping a
+   * single object in isolation (no de-duplication opportunity since there's nothing else in
+   * scope to de-duplicate against).
+   */
+  default TARGET map(SOURCE source) {
+    return map(source, new DtoMapContext());
+  }
+
+  /**
+   * Map a list of source instances to a list of target DTOs sharing the given context,
+   * preserving order.
+   */
+  default List<TARGET> mapList(List<SOURCE> source, DtoMapContext context) {
+    List<TARGET> result = new ArrayList<>(source.size());
+    for (SOURCE s : source) {
+      result.add(map(s, context));
+    }
+    return result;
+  }
+
+  /**
+   * Map a list of source instances to a list of target DTOs using a fresh context shared across
+   * the whole list - this is the usual top-level entry point, e.g. mapping the result of a
+   * {@code query.findList()} call.
+   */
+  default List<TARGET> mapList(List<SOURCE> source) {
+    return mapList(source, new DtoMapContext());
+  }
+}

ebean-api/src/main/java/io/ebean/DtoMapperManager.java

@@ -0,0 +1,125 @@
+package io.ebean;
+
+import io.ebean.config.DtoMapperRegister;
+import jakarta.persistence.PersistenceException;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.ServiceLoader;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Loads all generated {@link DtoMapperRegister} implementations (via {@code ServiceLoader},
+ * mirroring how {@code EntityClassRegister} is discovered) once, and resolves the {@link
+ * DtoMapper} for a given (source, dto) pair, or by the generated mapper's own concrete type, on
+ * request.
+ * <p>
+ * Has no dependency on {@link Database} - it can be constructed independently, before (or
+ * without) a {@code Database} existing at all, e.g. as a DI-managed singleton constructed
+ * alongside the rest of an application's dependency graph. If you want the exact same instance
+ * (and hence the exact same underlying mapper instances) shared between {@code query.mapTo(...)}
+ * and your own application code, construct it yourself and register it via {@code
+ * DatabaseBuilder.putServiceObject(DtoMapperManager.class, myManager)} before building the {@code
+ * Database} - it is then used instead of a Database-internal default instance.
+ * <p>
+ * Resolved mappers are cached so that repeated lookups only ever pay the cost of iterating the
+ * generated registers and constructing the mapper (and its nested mapper/{@code FetchGroup}
+ * graph) once - after that, every lookup is a single hash-map hit regardless of how many entity/
+ * DTO pairs are registered.
+ */
+public final class DtoMapperManager {
+
+  private final List<DtoMapperRegister> registers;
+  private final ConcurrentHashMap<MapperKey, DtoMapper<?, ?>> pairCache = new ConcurrentHashMap<>();
+  private final ConcurrentHashMap<Class<?>, Object> typeCache = new ConcurrentHashMap<>();
+
+  public DtoMapperManager() {
+    this.registers = load();
+  }
+
+  private static List<DtoMapperRegister> load() {
+    List<DtoMapperRegister> result = new ArrayList<>();
+    for (DtoMapperRegister register : ServiceLoader.load(DtoMapperRegister.class)) {
+      result.add(register);
+    }
+    return result;
+  }
+
+  /**
+   * Return the {@link DtoMapper} for the given (source, dto) pair.
+   *
+   * @throws PersistenceException if no generated mapper is registered for that pair.
+   */
+  @SuppressWarnings("unchecked")
+  public <S, D> DtoMapper<S, D> mapperFor(Class<S> sourceType, Class<D> dtoType) {
+    return (DtoMapper<S, D>) pairCache.computeIfAbsent(new MapperKey(sourceType, dtoType), this::resolve);
+  }
+
+  /**
+   * Return the generated mapper instance of the given concrete mapper type - e.g. {@code
+   * manager.get(CustomerDtoMapper.class)} - typically used to resolve a mapper instance for
+   * dependency injection into application code (e.g. an avaje-inject {@code @Factory} bean
+   * method).
+   *
+   * @throws PersistenceException if no generated mapper of that type is registered.
+   */
+  @SuppressWarnings("unchecked")
+  public <T> T get(Class<T> mapperType) {
+    return (T) typeCache.computeIfAbsent(mapperType, this::resolveByType);
+  }
+
+  private DtoMapper<?, ?> resolve(MapperKey key) {
+    for (DtoMapperRegister register : registers) {
+      DtoMapper<?, ?> mapper = register.mapperFor(key.sourceType, key.dtoType);
+      if (mapper != null) {
+        return mapper;
+      }
+    }
+    throw new PersistenceException("No DtoMapper registered mapping " + key.sourceType + " -> " + key.dtoType
+      + " - check @DtoMapping(source = " + key.sourceType.getSimpleName() + ".class, target = "
+      + key.dtoType.getSimpleName() + ".class) is declared on a package-info.java processed by querybean-generator");
+  }
+
+  private Object resolveByType(Class<?> mapperType) {
+    for (DtoMapperRegister register : registers) {
+      Object mapper = register.mapperOfType(mapperType);
+      if (mapper != null) {
+        return mapper;
+      }
+    }
+    throw new PersistenceException("No DtoMapper of type " + mapperType.getName() + " registered"
+      + " - check a @DtoMapping(...) pair generating " + mapperType.getSimpleName()
+      + " is declared on a package-info.java processed by querybean-generator");
+  }
+
+  /**
+   * Cache key pairing the source entity type and target DTO type.
+   */
+  private static final class MapperKey {
+
+    private final Class<?> sourceType;
+    private final Class<?> dtoType;
+
+    MapperKey(Class<?> sourceType, Class<?> dtoType) {
+      this.sourceType = sourceType;
+      this.dtoType = dtoType;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (!(o instanceof MapperKey)) {
+        return false;
+      }
+      MapperKey other = (MapperKey) o;
+      return sourceType == other.sourceType && dtoType == other.dtoType;
+    }
+
+    @Override
+    public int hashCode() {
+      return 31 * sourceType.hashCode() + dtoType.hashCode();
+    }
+  }
+}

ebean-api/src/main/java/io/ebean/ExpressionList.java

@@ -103,6 +103,29 @@ public interface ExpressionList<T> {
    */
   <D> DtoQuery<D> asDto(Class<D> dtoClass);
 
+  /**
+   * Map the query result to a nested DTO graph, automatically deriving the select()/fetch() spec
+   * from the target DTO's declared shape and forcing {@code setUnmodifiable(true)}.
+   * <p>
+   * Distinct from {@link #asDto(Class)} (the flat, single-row SQL pipeline) - this supports
+   * nested ToOne/ToMany DTO graphs, mapped from the normal ORM entity query result.
+   *
+   * @throws jakarta.persistence.PersistenceException if no generated {@link DtoMapper} is
+   *     registered for this (entity, dto) pair.
+   */
+  <D> MappedQuery<D> mapTo(Class<D> dtoType);
+
+  /**
+   * Map the query result to a nested DTO graph using an already-resolved {@link DtoMapper}
+   * instance, rather than looking one up by (entity, dtoType) - e.g. to select a named variant
+   * mapper (see {@code @DtoMapping(name = "...", exclude = "...")}), such as
+   * {@code query.mapTo(User.class, userMapper.noFleets())}.
+   *
+   * @param dtoType the DTO type mapped to (must match {@code mapper}'s target type)
+   * @param mapper the mapper instance to use, e.g. a named variant accessor on a generated mapper
+   */
+  <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper);
+
   /**
    * Return the underlying query as an UpdateQuery.
    * <p>

ebean-api/src/main/java/io/ebean/MappedQuery.java

@@ -0,0 +1,92 @@
+package io.ebean;
+
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+import java.sql.Connection;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+/**
+ * Query that maps an entity graph query result to a nested DTO graph, produced by
+ * {@code query.mapTo(SomeDto.class)}.
+ * <p>
+ * Distinct from the existing flat, single-row {@link DtoQuery} pipeline (see {@link
+ * QueryBuilder#asDto(Class)}) - this executes the underlying entity ORM query (with the
+ * select()/fetch() spec automatically derived from the target DTO's declared shape, see
+ * {@link DtoMapper#fetchGroup()}), forces {@code setUnmodifiable(true)}, and then maps the
+ * resulting (unmodifiable) entity graph into a DTO graph via the generated {@link DtoMapper},
+ * supporting nested ToOne/ToMany and identity-aware de-duplication.
+ *
+ * @param <D> the target DTO type
+ */
+@NullMarked
+public interface MappedQuery<D> {
+
+  /**
+   * Execute the query returning the mapped DTO list.
+   */
+  List<D> findList();
+
+  /**
+   * Execute the query returning a paged list of mapped DTOs.
+   * <p>
+   * Mirrors {@code Query#findPagedList()} - the underlying entity graph query is paged (via
+   * {@code setFirstRow(int)}/{@code setMaxRows(int)}) and executed as normal, then each page's
+   * result is mapped to the target DTO graph. Row-count/page-index metadata
+   * ({@link PagedList#getTotalCount()}, {@link PagedList#hasNext()}, etc.) reflects the
+   * underlying entity query and is unaffected by the DTO mapping.
+   */
+  PagedList<D> findPagedList();
+
+  /**
+   * Execute the query returning the result as a Stream of mapped DTOs.
+   * <p>
+   * Mirrors {@link QueryBuilder#findStream()} - the underlying entity graph query is streamed
+   * (supporting very large queries iterating any number of results, potentially using multiple
+   * persistence contexts internally) and each entity is mapped to its target DTO lazily as the
+   * stream is consumed, sharing one {@link DtoMapContext} across the whole stream so that
+   * repeated references to the same source entity still de-duplicate to the same DTO instance.
+   * <pre>{@code
+   *
+   *  // use try with resources to ensure Stream is closed
+   *
+   *  try (Stream<CustomerDto> stream = query.mapTo(CustomerDto.class).findStream()) {
+   *    stream
+   *    .map(...)
+   *    .collect(...);
+   *  }
+   *
+   * }</pre>
+   */
+  Stream<D> findStream();
+
+  /**
+   * Execute the query returning a single mapped DTO, or {@code null} if there is no matching row.
+   */
+  @Nullable
+  D findOne();
+
+  /**
+   * Execute the query returning an optional mapped DTO.
+   */
+  Optional<D> findOneOrEmpty();
+
+  /**
+   * Ensure the master DataSource is used when useMaster is true. Otherwise, the read only
+   * data source can be used if defined.
+   */
+  MappedQuery<D> usingMaster(boolean useMaster);
+
+  /**
+   * Use the explicit transaction to execute the query.
+   */
+  MappedQuery<D> usingTransaction(Transaction transaction);
+
+  /**
+   * Execute the query using the given connection.
+   */
+  MappedQuery<D> usingConnection(Connection connection);
+
+}

ebean-api/src/main/java/io/ebean/QueryBuilder.java

@@ -77,6 +77,32 @@ public interface QueryBuilder<SELF extends QueryBuilder<SELF, T>, T> extends Que
    */
   <D> DtoQuery<D> asDto(Class<D> dtoClass);
 
+  /**
+   * Map the query result to a nested DTO graph, automatically deriving the select()/fetch() spec
+   * from the target DTO's declared shape and forcing {@code setUnmodifiable(true)}.
+   * <p>
+   * Distinct from {@link #asDto(Class)} (the flat, single-row SQL pipeline) - this supports
+   * nested ToOne/ToMany DTO graphs, mapped from the normal ORM entity query result.
+   *
+   * @throws jakarta.persistence.PersistenceException if no generated {@link DtoMapper} is
+   *     registered for this (entity, dto) pair.
+   */
+  <D> MappedQuery<D> mapTo(Class<D> dtoType);
+
+  /**
+   * Map the query result to a nested DTO graph using an already-resolved {@link DtoMapper}
+   * instance, rather than looking one up by (entity, dtoType). Bypasses {@link DtoMapperManager}
+   * entirely, so it's the way to select a named variant mapper (see {@code @DtoMapping(name =
+   * "...", exclude = "...")}) - e.g. {@code query.mapTo(User.class, userMapper.noFleets())}.
+   * <p>
+   * Also forces {@code setUnmodifiable(true)} and derives the select()/fetch() spec from
+   * {@code mapper.fetchGroup()}, same as {@link #mapTo(Class)}.
+   *
+   * @param dtoType the DTO type mapped to (must match {@code mapper}'s target type)
+   * @param mapper the mapper instance to use, e.g. a named variant accessor on a generated mapper
+   */
+  <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper);
+
   /**
    * Convert the query to a UpdateQuery.
    * <p>

ebean-api/src/main/java/io/ebean/config/DtoMapperRegister.java

@@ -0,0 +1,31 @@
+package io.ebean.config;
+
+import io.ebean.DtoMapper;
+
+/**
+ * Loads and returns the {@link DtoMapper} to use for a given DTO type, generated per-module by
+ * the querybean-generator annotation processor for each {@code io.ebean.annotation.DtoMapping}
+ * registered pair.
+ * <p>
+ * Implementations resolve purely via literal {@code Class} comparisons (no reflection,
+ * {@code Class.forName}, or {@code MethodHandles}) - safe under GraalVM native-image with zero
+ * additional reachability metadata - mirroring {@link EntityClassRegister}.
+ */
+public interface DtoMapperRegister {
+
+  /**
+   * Return the mapper for the given DTO type, or {@code null} if this register has no mapper for
+   * that type.
+   */
+  <SOURCE,TARGET> DtoMapper<SOURCE, TARGET> mapperFor(Class<SOURCE> sourceType, Class<TARGET> targetType);
+
+  /**
+   * Return the mapper instance of the given concrete generated mapper type, or {@code null} if
+   * this register has no mapper of that type.
+   * <p>
+   * An alternative to {@link #mapperFor(Class, Class)} for looking up a mapper by its own class
+   * (e.g. {@code CustomerDtoMapper.class}) rather than by its (source, target) pair - typically
+   * used to resolve a mapper instance for dependency injection into application code.
+   */
+  <T> T mapperOfType(Class<T> mapperType);
+}

ebean-core/src/main/java/io/ebeaninternal/api/SpiEbeanServer.java

@@ -294,6 +294,16 @@ public interface SpiEbeanServer extends SpiServer, BeanCollectionLoader {
    */
   <D> DtoQuery<D> findDto(Class<D> dtoType, SpiQuery<?> ormQuery);
 
+  /**
+   * Return the generated {@link DtoMapper} for mapping the given source entity type to the given
+   * DTO type, discovered (via {@code ServiceLoader}) from the {@code DtoMapperRegister}s
+   * generated by {@code querybean-generator} - used by {@code query.mapTo(dtoType)}.
+   *
+   * @throws jakarta.persistence.PersistenceException if no mapper is registered for that
+   *     (source, dto) pair.
+   */
+  <S, D> DtoMapper<S, D> dtoMapper(Class<S> sourceType, Class<D> dtoType);
+
   /**
    * Execute the underlying ORM query returning as a JDBC ResultSet to map to DTO beans.
    */

ebean-core/src/main/java/io/ebeaninternal/api/SpiExpressionValidation.java

@@ -12,6 +12,7 @@ public final class SpiExpressionValidation {
 
   private final BeanType<?> desc;
   private final LinkedHashSet<String> unknown = new LinkedHashSet<>();
+  private final LinkedHashSet<String> all = new LinkedHashSet<>();
 
   public SpiExpressionValidation(BeanType<?> desc) {
     this.desc = desc;
@@ -21,6 +22,7 @@ public final class SpiExpressionValidation {
    * Validate that the property expression (path) is valid.
    */
   public void validate(String propertyName) {
+    all.add(propertyName);
     if (!desc.isValidExpression(propertyName)) {
       unknown.add(propertyName);
     }
@@ -33,4 +35,14 @@ public final class SpiExpressionValidation {
     return unknown;
   }
 
+  /**
+   * Return the set of all property names visited during this validation, regardless of
+   * whether they were considered valid against the bean type. Used to inspect the shape of
+   * an expression (for example, to check whether it references any associated/joined path)
+   * without needing a correctly-typed bean descriptor.
+   */
+  public Set<String> allProperties() {
+    return all;
+  }
+
 }

ebean-core/src/main/java/io/ebeaninternal/server/core/DefaultServer.java

@@ -90,6 +90,7 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
   private final DtoQueryEngine dtoQueryEngine;
   private final ServerCacheManager serverCacheManager;
   private final DtoBeanManager dtoBeanManager;
+  private final DtoMapperManager dtoMapperManager;
   private final BeanDescriptorManager descriptorManager;
   private final AutoTuneService autoTuneService;
   private final ReadAuditPrepare readAuditPrepare;
@@ -122,6 +123,7 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
   public DefaultServer(InternalConfiguration config, ServerCacheManager cache) {
     this.logManager = config.getLogManager();
     this.dtoBeanManager = config.getDtoBeanManager();
+    this.dtoMapperManager = config.getDtoMapperManager();
     this.config = config.getConfig();
     this.disableL2Cache = this.config.isDisableL2Cache();
     this.serverCacheManager = cache;
@@ -899,6 +901,11 @@ public final class DefaultServer implements SpiServer, SpiEbeanServer {
     return new DefaultDtoQuery<>(this, descriptor, ormQuery);
   }
 
+  @Override
+  public <S, D> DtoMapper<S, D> dtoMapper(Class<S> sourceType, Class<D> dtoType) {
+    return dtoMapperManager.mapperFor(sourceType, dtoType);
+  }
+
   @Override
   public SpiResultSet findResultSet(SpiQuery<?> ormQuery) {
     SpiOrmQueryRequest<?> request = createQueryRequest(ormQuery.type(), ormQuery);

ebean-core/src/main/java/io/ebeaninternal/server/core/InternalConfiguration.java

@@ -2,6 +2,7 @@ package io.ebeaninternal.server.core;
 
 import io.avaje.json.stream.JsonStream;
 import io.ebean.DatabaseBuilder;
+import io.ebean.DtoMapperManager;
 import io.ebean.ExpressionFactory;
 import io.ebean.annotation.Platform;
 import io.ebean.cache.*;
@@ -76,6 +77,7 @@ public final class InternalConfiguration {
   private final DeployInherit deployInherit;
   private final TypeManager typeManager;
   private final DtoBeanManager dtoBeanManager;
+  private final DtoMapperManager dtoMapperManager;
   private final Clock clock;
   private final DataTimeZone dataTimeZone;
   private final Binder binder;
@@ -125,6 +127,7 @@ public final class InternalConfiguration {
 
     final InternalConfigXmlMap xmlMap = initExternalMapping();
     this.dtoBeanManager = new DtoBeanManager(typeManager, xmlMap.readDtoMapping());
+    this.dtoMapperManager = initDtoMapperManager();
     this.dataSourceSupplier = createDataSourceSupplier();
     this.beanDescriptorManager = new BeanDescriptorManager(this);
     Map<String, String> asOfTableMapping = beanDescriptorManager.deploy(xmlMap.xmlDeployment());
@@ -153,6 +156,17 @@ public final class InternalConfiguration {
     }
   }
 
+  /**
+   * Use an application-provided {@link DtoMapperManager} (registered via {@code
+   * config.putServiceObject(DtoMapperManager.class, ...)} before building the Database) if
+   * present, so the exact same instance (and hence the same underlying mapper instances) can be
+   * shared between {@code query.mapTo(...)} and application code, otherwise construct a default.
+   */
+  private DtoMapperManager initDtoMapperManager() {
+    DtoMapperManager manager = config.getServiceObject(DtoMapperManager.class);
+    return manager != null ? manager : new DtoMapperManager();
+  }
+
   private List<XmapEbean> readExternalMapping() {
     final XmapService xmapService = service(XmapService.class);
     if (xmapService == null) {
@@ -520,6 +534,10 @@ public final class InternalConfiguration {
     return dtoBeanManager;
   }
 
+  DtoMapperManager getDtoMapperManager() {
+    return dtoMapperManager;
+  }
+
   SpiLogManager getLogManager() {
     return logManager;
   }

ebean-core/src/main/java/io/ebeaninternal/server/deploy/DbSqlContext.java

@@ -181,4 +181,11 @@ public interface DbSqlContext {
    * Include the filter many predicates if specified into the JOIN clause.
    */
   void includeFilterMany();
+
+  /**
+   * Return true if the given fetch path (relative to the query root) is the exact join clause
+   * that the pending filterMany predicate must be attached to - i.e. the deepest path the
+   * filterMany expression itself references.
+   */
+  boolean isFilterManyAttachPoint(String prefix);
 }

ebean-core/src/main/java/io/ebeaninternal/server/expression/DefaultExpressionList.java

@@ -254,17 +254,27 @@ public class DefaultExpressionList<T> implements SpiExpressionList<T> {
 
   @Override
   public Query<T> asOf(Timestamp asOf) {
-    return query.asOf(asOf);
+    return query().asOf(asOf);
   }
 
   @Override
   public Query<T> asDraft() {
-    return query.asDraft();
+    return query().asDraft();
   }
 
   @Override
   public <D> DtoQuery<D> asDto(Class<D> dtoClass) {
-    return query.asDto(dtoClass);
+    return query().asDto(dtoClass);
+  }
+
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType) {
+    return query().mapTo(dtoType);
+  }
+
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper) {
+    return query().mapTo(dtoType, mapper);
   }
 
   @Override

ebean-core/src/main/java/io/ebeaninternal/server/expression/JunctionExpression.java

@@ -367,6 +367,16 @@ final class JunctionExpression<T> implements SpiJunction<T>, SpiExpression, Expr
     return exprList.asDto(dtoClass);
   }
 
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType) {
+    return exprList.mapTo(dtoType);
+  }
+
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper) {
+    return exprList.mapTo(dtoType, mapper);
+  }
+
   @Override
   public UpdateQuery<T> asUpdate() {
     return exprList.asUpdate();

ebean-core/src/main/java/io/ebeaninternal/server/query/CQueryPredicates.java

@@ -78,6 +78,11 @@ public final class CQueryPredicates {
    */
   private Set<String> predicateIncludes;
   private Set<String> orderByIncludes;
+  /**
+   * The fetch path (relative to the query root) of the many-root whose own join clause the
+   * filterMany-in-JOIN predicate is attached to
+   */
+  private String filterManyAttachPath;
 
   CQueryPredicates(Binder binder, OrmQueryRequest<?> request) {
     this.binder = binder;
@@ -222,6 +227,8 @@ public final class CQueryPredicates {
           filterMany = new DefaultExpressionRequest(request, deployParser, binder, filterManyExpr);
           if (buildSql) {
             dbFilterMany = filterMany.buildSql();
+            // safe as filterManyJoin only holds when the expression is root-property only -
+            filterManyAttachPath = manyProperty.path();
           }
         }
       }
@@ -399,6 +406,14 @@ public final class CQueryPredicates {
     return filterManyJoin ? dbFilterMany : null;
   }
 
+  /**
+   * Return the fetch path of the filterMany-in-JOIN predicate - the path whose own join clause
+   * the predicate must be appended to (or null if there is no filterMany-in-JOIN predicate at all).
+   */
+  String filterManyAttachPath() {
+    return filterManyJoin ? filterManyAttachPath : null;
+  }
+
   /**
    * Return the db column version of the order by clause.
    */

ebean-core/src/main/java/io/ebeaninternal/server/query/DefaultDbSqlContext.java

@@ -23,6 +23,7 @@ final class DefaultDbSqlContext implements DbSqlContext {
   private final ArrayStack<String> prefixStack = new ArrayStack<>();
   private final String fromForUpdate;
   private final String dbFilterManyJoin;
+  private final String filterManyAttachPath;
   private boolean useColumnAlias;
   private int columnIndex;
   private int asOfTableCount;
@@ -42,7 +43,8 @@ final class DefaultDbSqlContext implements DbSqlContext {
   private boolean joinSuppressed;
 
   DefaultDbSqlContext(SqlTreeAlias alias, String columnAliasPrefix, CQueryHistorySupport historySupport,
-                      CQueryDraftSupport draftSupport, String fromForUpdate, String dbFilterManyJoin) {
+                      CQueryDraftSupport draftSupport, String fromForUpdate, String dbFilterManyJoin,
+                      String filterManyAttachPath) {
     this.alias = alias;
     this.columnAliasPrefix = columnAliasPrefix;
     this.useColumnAlias = columnAliasPrefix != null;
@@ -51,6 +53,12 @@ final class DefaultDbSqlContext implements DbSqlContext {
     this.historyQuery = (historySupport != null);
     this.fromForUpdate = fromForUpdate;
     this.dbFilterManyJoin = dbFilterManyJoin;
+    this.filterManyAttachPath = filterManyAttachPath;
+  }
+
+  @Override
+  public boolean isFilterManyAttachPoint(String prefix) {
+    return dbFilterManyJoin != null && filterManyAttachPath != null && filterManyAttachPath.equals(prefix);
   }
 
   @Override

ebean-core/src/main/java/io/ebeaninternal/server/query/DefaultFetchGroupQuery.java

@@ -149,6 +149,16 @@ final class DefaultFetchGroupQuery<T> implements SpiFetchGroupQuery<T>, SpiQuery
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
   }
 
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType) {
+    throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
+  }
+
+  @Override
+  public <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper) {
+    throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
+  }
+
   @Override
   public UpdateQuery<T> asUpdate() {
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");

ebean-core/src/main/java/io/ebeaninternal/server/query/SqlTreeBuilder.java

@@ -108,7 +108,7 @@ public final class SqlTreeBuilder {
     CQueryHistorySupport historySupport = builder.historySupport(query);
     CQueryDraftSupport draftSupport = builder.draftSupport(query);
     String colAlias = subQuery || rootNode.isSingleProperty() ? null : columnAliasPrefix;
-    this.ctx = new DefaultDbSqlContext(alias, colAlias, historySupport, draftSupport, fromForUpdate, predicates.dbFilterManyJoin());
+    this.ctx = new DefaultDbSqlContext(alias, colAlias, historySupport, draftSupport, fromForUpdate, predicates.dbFilterManyJoin(), predicates.filterManyAttachPath());
   }
 
   /**

ebean-core/src/main/java/io/ebeaninternal/server/query/SqlTreeNodeBean.java

@@ -342,6 +342,10 @@ class SqlTreeNodeBean implements SqlTreeNode {
     if (desc.isSoftDelete() && temporalMode != SpiQuery.TemporalMode.SOFT_DELETED) {
       ctx.append(" and ").append(desc.softDeletePredicate(ctx.tableAlias(prefix)));
     }
+    if (prefix != null && ctx.isFilterManyAttachPoint(prefix)) {
+      // this node is where we inline the filterMany predicate
+      ctx.includeFilterMany();
+    }
     return sqlJoinType;
   }
 

ebean-core/src/main/java/io/ebeaninternal/server/query/SqlTreeNodeManyRoot.java

@@ -45,6 +45,5 @@ final class SqlTreeNodeManyRoot extends SqlTreeNodeBean {
   @Override
   public void appendFrom(DbSqlContext ctx, SqlJoinType joinType) {
     super.appendFrom(ctx, joinType.autoToOuter());
-    ctx.includeFilterMany();
   }
 }

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/DefaultMappedQuery.java

@@ -0,0 +1,123 @@
+package io.ebeaninternal.server.querydefn;
+
+import io.ebean.DtoMapContext;
+import io.ebean.DtoMapper;
+import io.ebean.MappedQuery;
+import io.ebean.PagedList;
+import io.ebean.Transaction;
+import io.ebeaninternal.api.SpiEbeanServer;
+import io.ebeaninternal.api.SpiQuery;
+
+import java.sql.Connection;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Stream;
+
+/**
+ * Default implementation of {@link MappedQuery} backing {@code query.mapTo(dtoType)}.
+ * <p>
+ * Resolves the generated {@link DtoMapper} for the query's (entity, dto) pair, applies its
+ * {@link DtoMapper#fetchGroup()} (derived from the target DTO's declared shape) - unless the
+ * caller has already specified their own {@code select()}/{@code fetch()} spec, in which case
+ * that manual spec is left untouched - and forces {@code setUnmodifiable(true)} on the
+ * underlying query before it is executed, then maps the resulting entity graph into the
+ * target DTO graph.
+ */
+public final class DefaultMappedQuery<T, D> implements MappedQuery<D> {
+
+  private final SpiEbeanServer server;
+  private final SpiQuery<T> query;
+  private final Class<D> dtoType;
+  private DtoMapper<T, D> mapper;
+  private boolean applied;
+
+  public DefaultMappedQuery(SpiEbeanServer server, SpiQuery<T> query, Class<D> dtoType) {
+    this.server = server;
+    this.query = query;
+    this.dtoType = dtoType;
+  }
+
+  /**
+   * Use an already-resolved mapper instance directly - e.g. a named variant accessor on a
+   * generated mapper, such as {@code query.mapTo(User.class, userMapper.noFleets())} - bypassing
+   * {@code server.dtoMapper(...)} lookup entirely.
+   */
+  public DefaultMappedQuery(SpiEbeanServer server, SpiQuery<T> query, Class<D> dtoType, DtoMapper<T, D> mapper) {
+    this.server = server;
+    this.query = query;
+    this.dtoType = dtoType;
+    this.mapper = mapper;
+  }
+
+  /**
+   * Apply the mapper's fetch spec + unmodifiable to the underlying query (once) - must happen
+   * before the query is executed. Uses an explicit {@code applied} flag rather than a
+   * {@code mapper == null} check since a pre-supplied mapper (see the constructor above) is
+   * already non-null before the fetch spec has been applied.
+   */
+  private DtoMapper<T, D> mapper() {
+    if (!applied) {
+      if (mapper == null) {
+        mapper = server.dtoMapper(query.getBeanType(), dtoType);
+      }
+      if (query.detail().isEmpty()) {
+        // only apply the mapper's derived fetch spec if the caller hasn't already specified
+        // their own select()/fetch() - allowing manual query tuning/optimisation to take
+        // precedence over the DTO shape's default fetch spec when needed
+        query.select(mapper.fetchGroup());
+      }
+      query.setUnmodifiable(true);
+      applied = true;
+    }
+    return mapper;
+  }
+
+
+  @Override
+  public List<D> findList() {
+    DtoMapper<T, D> m = mapper();
+    return m.mapList(query.findList());
+  }
+
+  @Override
+  public D findOne() {
+    DtoMapper<T, D> m = mapper();
+    return m.map(query.findOne());
+  }
+
+  @Override
+  public Optional<D> findOneOrEmpty() {
+    return Optional.ofNullable(findOne());
+  }
+
+  @Override
+  public PagedList<D> findPagedList() {
+    DtoMapper<T, D> m = mapper();
+    return new MappedPagedList<>(query.findPagedList(), m);
+  }
+
+  @Override
+  public Stream<D> findStream() {
+    DtoMapper<T, D> m = mapper();
+    DtoMapContext context = new DtoMapContext();
+    return query.findStream().map(source -> m.map(source, context));
+  }
+
+  @Override
+  public MappedQuery<D> usingMaster(boolean useMaster) {
+    query.usingMaster(useMaster);
+    return this;
+  }
+
+  @Override
+  public MappedQuery<D> usingTransaction(Transaction transaction) {
+    query.usingTransaction(transaction);
+    return this;
+  }
+
+  @Override
+  public MappedQuery<D> usingConnection(Connection connection) {
+    query.usingConnection(connection);
+    return this;
+  }
+}

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/DefaultOrmQuery.java

@@ -184,6 +184,16 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
     return server.findDto(dtoClass, this);
   }
 
+  @Override
+  public final <D> MappedQuery<D> mapTo(Class<D> dtoType) {
+    return new DefaultMappedQuery<>(server, this, dtoType);
+  }
+
+  @Override
+  public final <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper) {
+    return new DefaultMappedQuery<>(server, this, dtoType, mapper);
+  }
+
   @Override
   public final UpdateQuery<T> asUpdate() {
     return new DefaultUpdateQuery<>(this);

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/MappedPagedList.java

@@ -0,0 +1,87 @@
+package io.ebeaninternal.server.querydefn;
+
+import io.ebean.DtoMapper;
+import io.ebean.PagedList;
+
+import java.util.List;
+import java.util.concurrent.Future;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * {@link PagedList} adapter backing {@code query.mapTo(dtoType).findPagedList()}.
+ * <p>
+ * Delegates all page metadata (total count, page index, {@code hasNext()}/{@code hasPrev()}, ...)
+ * straight through to the underlying entity-typed {@link PagedList} unchanged - paging is a
+ * property of the query, not of the DTO shape. Only {@link #getList()} differs: it maps the
+ * delegate's entity list to the target DTO list (once, cached) via the given {@link DtoMapper}.
+ */
+public final class MappedPagedList<T, D> implements PagedList<D> {
+
+  private final ReentrantLock lock = new ReentrantLock();
+  private final PagedList<T> delegate;
+  private final DtoMapper<T, D> mapper;
+  private List<D> mappedList;
+
+  public MappedPagedList(PagedList<T> delegate, DtoMapper<T, D> mapper) {
+    this.delegate = delegate;
+    this.mapper = mapper;
+  }
+
+  @Override
+  public void loadCount() {
+    delegate.loadCount();
+  }
+
+  @Override
+  public Future<Integer> getFutureCount() {
+    return delegate.getFutureCount();
+  }
+
+  @Override
+  public List<D> getList() {
+    lock.lock();
+    try {
+      if (mappedList == null) {
+        mappedList = mapper.mapList(delegate.getList());
+      }
+      return mappedList;
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  @Override
+  public int getTotalCount() {
+    return delegate.getTotalCount();
+  }
+
+  @Override
+  public int getTotalPageCount() {
+    return delegate.getTotalPageCount();
+  }
+
+  @Override
+  public int getPageSize() {
+    return delegate.getPageSize();
+  }
+
+  @Override
+  public int getPageIndex() {
+    return delegate.getPageIndex();
+  }
+
+  @Override
+  public boolean hasNext() {
+    return delegate.hasNext();
+  }
+
+  @Override
+  public boolean hasPrev() {
+    return delegate.hasPrev();
+  }
+
+  @Override
+  public String getDisplayXtoYofZ(String to, String of) {
+    return delegate.getDisplayXtoYofZ(to, of);
+  }
+}

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/OrmQueryDetail.java

@@ -384,14 +384,18 @@ public final class OrmQueryDetail implements Serializable {
         OrmQueryProperties chunk = pair.getProperties();
         if (isQueryJoinCandidate(lazyLoadManyPath, chunk)) {
           // this is a 'fetch join' (included in main query)
-          if (fetchJoinFirstMany) {
+          BeanDescriptor<?> targetDescriptor = ((BeanPropertyAssoc<?>) elProp.beanProperty()).targetDescriptor();
+          if (fetchJoinFirstMany && !chunk.filterManyHasNestedProperty(targetDescriptor)) {
             // letting the first one remain a 'fetch join'
             fetchJoinFirstMany = false;
             manyFetchProperty = pair.getPath();
             chunk.filterManyInline();
             many = elProp;
           } else {
-            // convert this one over to a 'query join'
+            // convert this one over to a 'query join' - either because another many has already claimed the
+            // 'fetch join' slot, or because its filterMany references a property that requires crossing into
+            // an associated bean and can't safely be included as a JOIN predicate (see
+            // OrmQueryProperties.filterManyHasNestedProperty)
             chunk.markForQueryJoin();
           }
         }

ebean-core/src/main/java/io/ebeaninternal/server/querydefn/OrmQueryProperties.java

@@ -9,7 +9,10 @@ import io.ebean.util.SplitName;
 import io.ebeaninternal.api.SpiExpression;
 import io.ebeaninternal.api.SpiExpressionFactory;
 import io.ebeaninternal.api.SpiExpressionList;
+import io.ebeaninternal.api.SpiExpressionValidation;
 import io.ebeaninternal.api.SpiQuery;
+import io.ebeaninternal.server.deploy.BeanDescriptor;
+import io.ebeaninternal.server.el.ElPropertyValue;
 import io.ebeaninternal.server.expression.FilterExprPath;
 import io.ebeaninternal.server.expression.FilterExpressionList;
 
@@ -234,6 +237,26 @@ public final class OrmQueryProperties implements Serializable {
     return filterMany != null && !markForQueryJoin;
   }
 
+  /**
+   * Return true if the filterMany expression (if any) references a property that requires
+   * crossing into an associated bean/join - e.g. {@code "group.name"} - rather than only
+   * plain/embedded properties resolving to columns on the many bean's own base table.
+   */
+  boolean filterManyHasNestedProperty(BeanDescriptor<?> targetDescriptor) {
+    if (filterMany == null) {
+      return false;
+    }
+    SpiExpressionValidation validation = new SpiExpressionValidation(targetDescriptor);
+    filterMany.validate(validation);
+    for (String property : validation.allProperties()) {
+      ElPropertyValue elProp = targetDescriptor.elGetValue(property);
+      if (elProp != null && elProp.isAssocProperty()) {
+        return true;
+      }
+    }
+    return false;
+  }
+
   /**
    * Adjust filterMany expressions for inclusion in main query.
    */

ebean-querybean/src/main/java/io/ebean/typequery/QueryBean.java

@@ -435,6 +435,16 @@ public abstract class QueryBean<T, R extends QueryBean<T, R>> implements IQueryB
     return query.asDto(dtoClass);
   }
 
+  @Override
+  public final <D> MappedQuery<D> mapTo(Class<D> dtoType) {
+    return query.mapTo(dtoType);
+  }
+
+  @Override
+  public final <D> MappedQuery<D> mapTo(Class<D> dtoType, DtoMapper<T, D> mapper) {
+    return query.mapTo(dtoType, mapper);
+  }
+
   @Override
   public final R setId(Object id) {
     query.setId(id);

ebean-redis/src/test/java/io/ebean/redis/RedisFlushExtension.java

@@ -0,0 +1,37 @@
+package io.ebean.redis;
+
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import redis.clients.jedis.Jedis;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Auto-detected JUnit5 extension (see {@code junit-platform.properties}) that flushes the shared
+ * Redis test container exactly once per JVM, before the first test class in this module runs.
+ *
+ * <p>The Redis test container is intentionally long-lived and reused across test runs - and even
+ * shared with the sibling ebean-redisson module (same fixed-name/fixed-port container) - to avoid
+ * restart cost, especially with parallel reactor builds. It is never flushed between runs. Without
+ * this, stale keys/counters left over from an earlier run can leak into hit/miss/TTL assertions
+ * that assume a cold cache, causing hard-to-reproduce flakiness.
+ */
+public class RedisFlushExtension implements BeforeAllCallback {
+
+  private static final AtomicBoolean FLUSHED = new AtomicBoolean();
+
+  @Override
+  public void beforeAll(ExtensionContext context) {
+    if (FLUSHED.compareAndSet(false, true)) {
+      flush();
+    }
+  }
+
+  private static void flush() {
+    try (Jedis jedis = new Jedis("localhost", 6379)) {
+      jedis.flushDB();
+    } catch (Exception e) {
+      // best effort - if Redis isn't reachable here, individual tests skip via their own checks
+    }
+  }
+}

ebean-redis/src/test/resources/META-INF/services/org.junit.jupiter.api.extension.Extension

@@ -0,0 +1 @@
+io.ebean.redis.RedisFlushExtension

ebean-redis/src/test/resources/junit-platform.properties

@@ -0,0 +1 @@
+junit.jupiter.extensions.autodetection.enabled=true

ebean-redisson/src/test/java/io/ebean/redisson/RedisFlushExtension.java

@@ -0,0 +1,55 @@
+package io.ebean.redisson;
+
+import org.junit.jupiter.api.extension.BeforeAllCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+import org.redisson.Redisson;
+import org.redisson.api.RedissonClient;
+import org.redisson.config.Config;
+
+import java.io.InputStream;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Auto-detected JUnit5 extension (see {@code junit-platform.properties}) that flushes the shared
+ * Redis test container exactly once per JVM, before the first test class in this module runs.
+ *
+ * <p>The Redis test container is intentionally long-lived and reused across test runs - and even
+ * shared with the sibling ebean-redis module (same fixed-name/fixed-port container) - to avoid
+ * restart cost, especially with parallel reactor builds. It is never flushed between runs. Without
+ * this, stale keys/counters left over from an earlier run can leak into hit/miss/TTL assertions
+ * that assume a cold cache, causing hard-to-reproduce flakiness.
+ */
+public class RedisFlushExtension implements BeforeAllCallback {
+
+  private static final AtomicBoolean FLUSHED = new AtomicBoolean();
+
+  @Override
+  public void beforeAll(ExtensionContext context) {
+    if (FLUSHED.compareAndSet(false, true)) {
+      flush();
+    }
+  }
+
+  private static void flush() {
+    try {
+      RedissonClient client = Redisson.create(loadConfig());
+      try {
+        client.getKeys().flushdb();
+      } finally {
+        client.shutdown();
+      }
+    } catch (Exception e) {
+      // best effort - if Redis isn't reachable here, individual tests skip via their own checks
+    }
+  }
+
+  private static Config loadConfig() {
+    InputStream is = RedisFlushExtension.class.getClassLoader().getResourceAsStream("redisson-config.yaml");
+    if (is != null) {
+      return Config.fromYAML(is);
+    }
+    Config cfg = new Config();
+    cfg.useSingleServer().setAddress("redis://localhost:6379");
+    return cfg;
+  }
+}

ebean-redisson/src/test/java/io/ebean/redisson/RedissonCacheFactoryTest.java

@@ -132,9 +132,20 @@ class RedissonCacheFactoryTest {
     ServerCacheNotify notify = factory.createCacheNotify(n -> {});
     notify.notify(new ServerCacheNotification(Set.of("orders", "items")));
 
-    Thread.sleep(500);
-    assertThat(received).isNotEmpty();
-    assertThat(received.get(0).getDependentTables()).contains("orders", "items");
+    // Wait (with polling rather than a single fixed sleep) for the expected notification to
+    // arrive. The shared "ebean.l2cache" topic is global/unscoped so other factories/tests in
+    // the same JVM (e.g. real entity saves elsewhere) can publish unrelated notifications on it
+    // around the same time - assert on content rather than position/count to stay robust to that.
+    long deadline = System.currentTimeMillis() + 2000;
+    boolean found = false;
+    while (System.currentTimeMillis() < deadline) {
+      found = received.stream().anyMatch(n -> n.getDependentTables().containsAll(Set.of("orders", "items")));
+      if (found) break;
+      Thread.sleep(50);
+    }
+    assertThat(found)
+      .as("Expected a notification with dependent tables [orders, items] in %s", received)
+      .isTrue();
   }
 
   @Test

ebean-redisson/src/test/resources/META-INF/services/org.junit.jupiter.api.extension.Extension

@@ -0,0 +1 @@
+io.ebean.redisson.RedisFlushExtension

ebean-redisson/src/test/resources/junit-platform.properties

@@ -0,0 +1 @@
+junit.jupiter.extensions.autodetection.enabled=true

ebean-test/src/test/java/io/ebean/xtest/internal/api/TDSpiEbeanServer.java

@@ -454,6 +454,11 @@ public class TDSpiEbeanServer extends TDSpiServer implements SpiEbeanServer {
     return null;
   }
 
+  @Override
+  public <S, D> DtoMapper<S, D> dtoMapper(Class<S> sourceType, Class<D> dtoType) {
+    return null;
+  }
+
   @Override
   public SpiResultSet findResultSet(SpiQuery<?> ormQuery) {
     return null;

ebean-test/src/test/java/org/tests/query/TestQueryFilterMany.java

@@ -174,7 +174,7 @@ public class TestQueryFilterMany extends BaseTestCase {
     assertThat(customers).isNotEmpty();
     List<String> sqlList = LoggedSql.stop();
     assertEquals(1, sqlList.size());
-    assertThat(sqlList.get(0)).contains(" left join o_customer t2 on t2.id = t1.kcustomer_id and t1.status = ? where ");
+    assertThat(sqlList.get(0)).contains(" left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and t1.status = ? left join o_customer t2 on t2.id = t1.kcustomer_id where ");
     assertThat(sqlList.get(0)).contains(" where lower(t0.name) = ? order by t0.id");
   }
 
@@ -211,7 +211,7 @@ public class TestQueryFilterMany extends BaseTestCase {
     assertThat(result).isNotEmpty();
     List<String> sql = LoggedSql.stop();
     assertThat(sql).hasSize(1);
-    assertThat(sql.get(0)).contains("from o_customer t0 left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null left join o_customer t2 on t2.id = t1.kcustomer_id and t1.order_date is not null order by t0.id");
+    assertThat(sql.get(0)).contains("from o_customer t0 left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and t1.order_date is not null left join o_customer t2 on t2.id = t1.kcustomer_id order by t0.id");
   }
 
   @Test
@@ -340,9 +340,9 @@ public class TestQueryFilterMany extends BaseTestCase {
     List<String> sqlList = LoggedSql.stop();
     assertEquals(1, sqlList.size());
     if (isPostgresCompatible()) {
-      assertThat(sqlList.get(0)).contains("left join o_customer t2 on t2.id = t1.kcustomer_id and t1.status = any(?) order by t0.id");
+      assertThat(sqlList.get(0)).contains("left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and t1.status = any(?) left join o_customer t2 on t2.id = t1.kcustomer_id order by t0.id");
     } else {
-      assertThat(sqlList.get(0)).contains("left join o_customer t2 on t2.id = t1.kcustomer_id and t1.status in (?) order by t0.id");
+      assertThat(sqlList.get(0)).contains("left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and t1.status in (?) left join o_customer t2 on t2.id = t1.kcustomer_id order by t0.id");
     }
   }
 
@@ -386,7 +386,7 @@ public class TestQueryFilterMany extends BaseTestCase {
 
     List<String> sql = LoggedSql.stop();
     assertEquals(1, sql.size());
-    assertSql(sql.get(0)).contains(" left join o_customer t2 on t2.id = t1.kcustomer_id and (t1.status = ? or t1.order_date = ?) order by t0.id");
+    assertSql(sql.get(0)).contains(" left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and (t1.status = ? or t1.order_date = ?) left join o_customer t2 on t2.id = t1.kcustomer_id order by t0.id");
   }
 
   @Test
@@ -459,7 +459,10 @@ public class TestQueryFilterMany extends BaseTestCase {
 
     List<String> sql = LoggedSql.stop();
 
-    assertThat(sql).hasSize(1);
-    assertSql(sql.get(0)).contains(" from o_customer t0 left join contact t1 on t1.customer_id = t0.id left join contact_group t2 on t2.id = t1.group_id and t2.name = ? and t1.cretime is not null order by t0.id");
+    // nested "group.name" reference forces this to a query join so the filter is applied
+    // as a genuine WHERE clause (not misapplied to a LEFT JOIN's ON clause)
+    assertThat(sql).hasSize(2);
+    assertSql(sql.get(1)).contains(" from contact t0 left join contact_group t1 on t1.id = t0.group_id where (t0.customer_id) in (");
+    assertSql(sql.get(1)).contains(" and t1.name = ? and t0.cretime is not null");
   }
 }

ebean-test/src/test/java/org/tests/query/TestQueryFilterManySimple.java

@@ -35,7 +35,7 @@ public class TestQueryFilterManySimple extends BaseTestCase {
     list.get(0).getOrders().size();
     List<String> sql = LoggedSql.stop();
     assertThat(sql).hasSize(2);
-    assertThat(sql.get(0)).contains("left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null left join o_customer t2 on t2.id = t1.kcustomer_id and t1.status = ? and t1.order_date > ?");
+    assertThat(sql.get(0)).contains("left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null and t1.status = ? and t1.order_date > ? left join o_customer t2 on t2.id = t1.kcustomer_id");
     assertThat(sql.get(0)).contains("order by t0.id");
     if (isPostgresCompatible()) {
       assertThat(sql.get(1)).contains("from contact t0 where (t0.customer_id) = any(?) and t0.first_name is not null;");
@@ -55,7 +55,10 @@ public class TestQueryFilterManySimple extends BaseTestCase {
       .findList();
 
     List<String> sql = LoggedSql.stop();
-    assertThat(sql).hasSize(1);
-    assertThat(sql.get(0)).contains("from o_customer t0 left join o_order t1 on t1.kcustomer_id = t0.id and t1.order_date is not null left join o_customer t2 on t2.id = t1.kcustomer_id and t2.status = ? order by t0.id");
+    // nested "customer.status" reference forces this to a query join so the filter is
+    // applied as a genuine WHERE clause (not misapplied to a LEFT JOIN's ON clause)
+    assertThat(sql).hasSize(2);
+    assertThat(sql.get(1)).contains("from o_order t0 join o_customer t1 on t1.id = t0.kcustomer_id where t0.order_date is not null and (t0.kcustomer_id) in (");
+    assertThat(sql.get(1)).contains(" and t1.status = ?");
   }
 }

ebean-test/src/test/java/org/tests/query/TestQueryFilterManyWithDeeperNestedFetch.java

@@ -0,0 +1,73 @@
+package org.tests.query;
+
+import io.ebean.DB;
+import io.ebean.test.LoggedSql;
+import io.ebean.xtest.BaseTestCase;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.Contact;
+import org.tests.model.basic.Customer;
+import org.tests.model.basic.ResetBasicData;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Reproduces a bug where filterMany() on a property of the many-root itself is misapplied
+ * to the ON clause of a deeper, unrelated nested fetch join instead of the many-root's own join
+ * clause - when an additional fetch path exists beneath the many property that the filterMany
+ * expression itself does not reference.
+ */
+public class TestQueryFilterManyWithDeeperNestedFetch extends BaseTestCase {
+
+  @Test
+  void filterMany_onRootProperty_withUnrelatedDeeperNestedFetch_expectFilterOnOwnJoin() {
+    ResetBasicData.reset();
+
+    Customer customer = DB.find(Customer.class).where().ieq("name", "Rob").findOne();
+    assertThat(customer).isNotNull();
+
+    List<Contact> allContacts = DB.find(Contact.class).where().eq("customer", customer).findList();
+    assertThat(allContacts).isNotEmpty();
+
+    // ensure at least one contact isMember=true and one isMember=false
+    Contact memberContact = allContacts.get(0);
+    memberContact.setMember(true);
+    DB.save(memberContact);
+    Contact nonMemberContact;
+    if (allContacts.size() > 1) {
+      nonMemberContact = allContacts.get(1);
+    } else {
+      nonMemberContact = new Contact();
+      nonMemberContact.setFirstName("Extra");
+      nonMemberContact.setLastName("NonMember");
+      nonMemberContact.setCustomer(customer);
+    }
+    nonMemberContact.setMember(false);
+    DB.save(nonMemberContact);
+
+    LoggedSql.start();
+    // filterMany only references "isMember" (a property of Contact - the many-root itself) but
+    // the query ALSO fetches a further nested path beneath "contacts" (contacts.group) that the
+    // filterMany expression does NOT reference at all.
+    List<Customer> found = DB.find(Customer.class)
+      .setBeanCacheMode(io.ebean.CacheMode.OFF)
+      .setPersistenceContextScope(io.ebean.PersistenceContextScope.QUERY)
+      .fetch("contacts", "id,firstName,lastName,isMember")
+      .fetch("contacts.group", "id,name")
+      .filterMany("contacts").eq("isMember", true)
+      .where().idEq(customer.getId())
+      .findList();
+
+    List<String> sql = LoggedSql.stop();
+    assertThat(found).isNotEmpty();
+    assertThat(sql).hasSize(1);
+    // the filterMany predicate must be on contact's own join (t1), not misapplied to the
+    // unrelated deeper contact_group join (t2)
+    assertThat(sql.get(0)).contains("left join contact t1 on t1.customer_id = t0.id and t1.is_member = ? left join contact_group t2 on t2.id = t1.group_id");
+
+    // every contact returned must be a member - the filter must actually exclude non-members
+    assertThat(found.get(0).getContacts()).isNotEmpty();
+    assertThat(found.get(0).getContacts()).allMatch(Contact::isMember);
+  }
+}

ebean-test/src/test/java/org/tests/query/TestUnmodifiableFetchStrategyAndPaging.java

@@ -0,0 +1,145 @@
+package org.tests.query;
+
+import io.ebean.DB;
+import io.ebean.LazyInitialisationException;
+import io.ebean.PagedList;
+import io.ebean.Paging;
+import io.ebean.test.LoggedSql;
+import io.ebean.xtest.BaseTestCase;
+import org.junit.jupiter.api.Test;
+import org.tests.model.basic.Contact;
+import org.tests.model.basic.Customer;
+import org.tests.model.basic.Order;
+import org.tests.model.basic.ResetBasicData;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Validates that fetch strategy (fetchQuery / fetchLazy secondary query hints) and pagination
+ * (setPaging / findPagedList) carry over correctly onto setUnmodifiable(true) entity graphs.
+ * <p>
+ * This is groundwork for issue #2540 (nested DTO mapping) - the plan is to map an unmodifiable
+ * entity graph into a nested DTO graph, so we need confidence that these existing query features
+ * continue to behave as expected on that unmodifiable graph.
+ */
+class TestUnmodifiableFetchStrategyAndPaging extends BaseTestCase {
+
+  @Test
+  void fetchQuery_withUnmodifiable_expectSecondaryQueryEagerlyLoadedAndUnmodifiable() {
+    ResetBasicData.reset();
+
+    LoggedSql.start();
+
+    List<Customer> customers = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .fetchQuery("contacts", "firstName,lastName")
+      .orderBy("id")
+      .findList();
+
+    List<String> sql = LoggedSql.stop();
+    // 1 query for customers + 1 secondary query for contacts (fetchQuery = eager secondary query)
+    assertThat(sql).hasSize(2);
+
+    assertThat(customers).isNotEmpty();
+    Customer customer = customers.get(0);
+    assertThat(DB.beanState(customer).isUnmodifiable()).isTrue();
+
+    // fetched via fetchQuery so already loaded - accessing it must not throw and must not
+    // trigger any further lazy loading query
+    LoggedSql.start();
+    List<Contact> contacts = customer.getContacts();
+    assertThat(LoggedSql.stop()).isEmpty();
+
+    assertThat(contacts).isNotEmpty();
+    Contact contact = contacts.get(0);
+    assertThat(DB.beanState(contact).isUnmodifiable()).isTrue();
+    assertThatThrownBy(() -> contact.setFirstName("junk"))
+      .isInstanceOf(io.ebean.UnmodifiableEntityException.class);
+  }
+
+  @Test
+  void fetchLazy_withUnmodifiable_expectNotEagerlyLoadedAndFailsFastOnAccess() {
+    ResetBasicData.reset();
+
+    LoggedSql.start();
+
+    List<Order> orders = DB.find(Order.class)
+      .setUnmodifiable(true)
+      .select("status")
+      .fetchLazy("customer", "name")
+      .findList();
+
+    List<String> sql = LoggedSql.stop();
+    // fetchLazy defers loading to first access - with disableLazyLoading (via unmodifiable)
+    // that deferred load can never happen, so only the root query should run
+    assertThat(sql).hasSize(1);
+
+    assertThat(orders).isNotEmpty();
+    Order order = orders.get(0);
+    assertThat(DB.beanState(order).isUnmodifiable()).isTrue();
+
+    // the *ToOne reference itself (just the foreign key / id) is available without lazy
+    // loading, so getCustomer() alone does not throw
+    Customer customerRef = order.getCustomer();
+    assertThat(customerRef).isNotNull();
+    assertThat(customerRef.getId()).isNotNull();
+
+    // but accessing a property that requires the fetchLazy relation to actually be loaded
+    // must fail fast rather than silently lazy load
+    assertThatThrownBy(customerRef::getName)
+      .isInstanceOf(LazyInitialisationException.class)
+      .hasMessageContaining("Property not loaded: name");
+  }
+
+  @Test
+  void setPaging_withUnmodifiable_expectCorrectSqlAndUnmodifiableResults() {
+    ResetBasicData.reset();
+
+    var paging = Paging.of(0, 2, "id");
+
+    LoggedSql.start();
+    List<Customer> customers = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .setPaging(paging)
+      .findList();
+    List<String> sql = LoggedSql.stop();
+
+    assertThat(sql).hasSize(1);
+    if (isLimitOffset()) {
+      assertThat(sql.get(0)).contains("order by t0.id limit 2");
+    }
+
+    assertThat(customers).hasSizeLessThanOrEqualTo(2);
+    for (Customer customer : customers) {
+      assertThat(DB.beanState(customer).isUnmodifiable()).isTrue();
+      assertThatThrownBy(() -> customer.setName("junk"))
+        .isInstanceOf(io.ebean.UnmodifiableEntityException.class);
+    }
+  }
+
+  @Test
+  void findPagedList_withUnmodifiable_expectTotalCountAndUnmodifiableResults() {
+    ResetBasicData.reset();
+
+    PagedList<Customer> pagedList = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .orderBy("id")
+      .setFirstRow(0)
+      .setMaxRows(2)
+      .findPagedList();
+
+    List<Customer> customers = pagedList.getList();
+    assertThat(customers).hasSizeLessThanOrEqualTo(2);
+    assertThat(pagedList.getTotalCount()).isGreaterThanOrEqualTo(customers.size());
+
+    for (Customer customer : customers) {
+      assertThat(DB.beanState(customer).isUnmodifiable()).isTrue();
+    }
+  }
+}

pom.xml

@@ -45,14 +45,14 @@
     <ebean-persistence-api.version>3.2</ebean-persistence-api.version>
     <ebean-types.version>3.0</ebean-types.version>
 
-    <ebean-annotation.version>8.5</ebean-annotation.version>
+    <ebean-annotation.version>8.6</ebean-annotation.version>
     <ebean-ddl-runner.version>2.3</ebean-ddl-runner.version>
     <ebean-migration-auto.version>1.2</ebean-migration-auto.version>
     <ebean-migration.version>14.3.0</ebean-migration.version>
     <ebean-test-containers.version>8.2</ebean-test-containers.version>
     <ebean-datasource.version>10.10</ebean-datasource.version>
-    <ebean-agent.version>18.1.0</ebean-agent.version>
-    <ebean-maven-plugin.version>18.1.0</ebean-maven-plugin.version>
+    <ebean-agent.version>18.3.0</ebean-agent.version>
+    <ebean-maven-plugin.version>18.3.0</ebean-maven-plugin.version>
     <surefire.useModulePath>false</surefire.useModulePath>
   </properties>
 

querybean-generator/pom.xml

@@ -11,6 +11,45 @@
   <artifactId>querybean-generator</artifactId>
   <description>Generates Ebean Query beans for type safe ORM query building and execution</description>
 
+  <properties>
+    <avaje.prisms.version>2.0</avaje.prisms.version>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>io.avaje</groupId>
+      <artifactId>avaje-prisms</artifactId>
+      <version>${avaje.prisms.version}</version>
+      <optional>true</optional>
+    </dependency>
+
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>ebean-annotation</artifactId>
+      <version>${ebean-annotation.version}</version>
+      <optional>true</optional>
+    </dependency>
+
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>jakarta-persistence-api</artifactId>
+      <version>${ebean-persistence-api.version}</version>
+      <scope>test</scope>
+    </dependency>
+
+    <!--
+      Test-only - lets DtoMapperRecordSourceTest fully compile a generated DTO mapper source
+      in-process (references io.ebean.DtoMapper/FetchGroup/etc.). Safe as a real dependency here
+      (unlike ebean-querybean) since ebean-api does not depend back on querybean-generator.
+    -->
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>ebean-api</artifactId>
+      <version>18.2.0</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
   <build>
     <plugins>
       <plugin>
@@ -19,8 +58,13 @@
         <configuration>
           <source>11</source>
           <target>11</target>
-          <!-- Turn off annotation processing for building -->
-          <compilerArgs>-proc:none</compilerArgs>
+          <annotationProcessorPaths>
+            <path>
+              <groupId>io.avaje</groupId>
+              <artifactId>avaje-prisms</artifactId>
+              <version>${avaje.prisms.version}</version>
+            </path>
+          </annotationProcessorPaths>
         </configuration>
       </plugin>
     </plugins>

querybean-generator/src/main/java/io/ebean/querybean/generator/Constants.java

@@ -26,6 +26,18 @@ interface Constants {
   String METAINF_MANIFEST = "META-INF/ebean-generated-info.mf";
   String METAINF_SERVICES_MODULELOADER = "META-INF/services/io.ebean.config.EntityClassRegister";
 
+  String DTO_MAPPING = "io.ebean.annotation.DtoMapping";
+  // DtoMapping is @Repeatable - when used more than once on the same element javac wraps
+  // the repeated instances in this synthetic container annotation instead, so it must also
+  // be registered as a supported annotation type or the processor is never invoked for it.
+  String DTO_MAPPING_LIST = "io.ebean.annotation.DtoMapping.List";
+  String DTO_PATH = "io.ebean.annotation.DtoPath";
+  String DTO_REF = "io.ebean.annotation.DtoRef";
+  String DTO_CONVERT = "io.ebean.annotation.DtoConvert";
+  String DTO_MIXIN = "io.ebean.annotation.DtoMixin";
+  String DTO_CONVERTER_MANAGER = "io.ebean.DtoConverterManager";
+  String METAINF_SERVICES_DTOMAPPERREGISTER = "META-INF/services/io.ebean.config.DtoMapperRegister";
+
   String AVAJE_LANG_NULLABLE = "org.jspecify.annotations.Nullable";
   String JAVA_COLLECTION = "java.util.Collection";
   String EXPRESSIONLIST = "io.ebean.ExpressionList";

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoBeanMeta.java

@@ -0,0 +1,134 @@
+package io.ebean.querybean.generator;
+
+import javax.lang.model.element.TypeElement;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Metadata for one {@code @DtoMapping(source, target)} pair - drives generation of a single
+ * {@code XxxMapper} class implementing {@code io.ebean.DtoMapper<source, target>}.
+ */
+class DtoBeanMeta {
+
+  private final TypeElement source;
+  private final TypeElement target;
+  private final String mapperPackage;
+  private final String mapperShortName;
+  private final String mapperFullName;
+  private final List<DtoPropertyMeta> properties = new ArrayList<>();
+  private final List<DtoMapperVariant> variants = new ArrayList<>();
+  private DtoBuilderMeta builderMeta;
+
+  /** Cycle detection state - see {@link DtoMappingReader#checkForCycles()}. */
+  enum Visit { WHITE, GRAY, BLACK }
+  Visit visit = Visit.WHITE;
+
+  /**
+   * Set true if this type is used as a {@code NESTED_ONE}/{@code NESTED_MANY} property by any
+   * other {@code @DtoMapping} pair - see {@link DtoMappingReader#markNestedElsewhere()}. Drives
+   * whether {@link DtoMapperWriter} needs to route this mapper's own construction through the
+   * {@code DtoMapContext} identity cache (only ever useful when the same source instance can be
+   * reached via more than one path in the graph).
+   */
+  private boolean nestedElsewhere;
+
+  DtoBeanMeta(TypeElement source, TypeElement target, String mapperPackage) {
+    this.source = source;
+    this.target = target;
+    this.mapperPackage = mapperPackage;
+    this.mapperShortName = target.getSimpleName().toString() + "Mapper";
+    this.mapperFullName = mapperPackage + "." + mapperShortName;
+  }
+
+  TypeElement source() {
+    return source;
+  }
+
+  TypeElement target() {
+    return target;
+  }
+
+  String mapperPackage() {
+    return mapperPackage;
+  }
+
+  String mapperShortName() {
+    return mapperShortName;
+  }
+
+  String mapperFullName() {
+    return mapperFullName;
+  }
+
+  String sourceFullName() {
+    return source.getQualifiedName().toString();
+  }
+
+  String targetFullName() {
+    return target.getQualifiedName().toString();
+  }
+
+  List<DtoPropertyMeta> properties() {
+    return properties;
+  }
+
+  void addProperty(DtoPropertyMeta property) {
+    properties.add(property);
+  }
+
+  List<DtoMapperVariant> variants() {
+    return variants;
+  }
+
+  void addVariant(DtoMapperVariant variant) {
+    variants.add(variant);
+  }
+
+  /**
+   * The detected+selected builder-based construction path for this target, or {@code null} if
+   * the mapper should construct the target via a plain positional constructor call instead - see
+   * {@link DtoMappingReader#resolveBuilder(DtoBeanMeta, String)}.
+   */
+  DtoBuilderMeta builderMeta() {
+    return builderMeta;
+  }
+
+  void builderMeta(DtoBuilderMeta builderMeta) {
+    this.builderMeta = builderMeta;
+  }
+
+  /**
+   * Return the distinct instance-dispatch {@code @DtoConvert} converters used by this mapper's
+   * properties (static-dispatch converters need no field/constructor wiring, so are excluded),
+   * in first-seen order, deduplicated by converter type - so a converter type used by more than
+   * one property still results in a single shared constructor parameter/field.
+   */
+  List<DtoConverterMeta> converterDeps() {
+    List<DtoConverterMeta> deps = new ArrayList<>();
+    for (DtoPropertyMeta property : properties) {
+      DtoConverterMeta converter = property.converter();
+      if (converter != null && !converter.isStatic() && !deps.contains(converter)) {
+        deps.add(converter);
+      }
+    }
+    return deps;
+  }
+
+  /**
+   * Return true if this type is nested ({@code NESTED_ONE}/{@code NESTED_MANY}) under some other
+   * DTO - i.e. the same source instance could be reached via more than one path in the graph, so
+   * identity de-duplication via {@code DtoMapContext} can actually matter for it.
+   */
+  boolean nestedElsewhere() {
+    return nestedElsewhere;
+  }
+
+  void markNestedElsewhere() {
+    this.nestedElsewhere = true;
+  }
+
+  @Override
+  public String toString() {
+    return sourceFullName() + " -> " + targetFullName();
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoBuilderMeta.java

@@ -0,0 +1,31 @@
+package io.ebean.querybean.generator;
+
+/**
+ * Metadata for a detected builder-style construction path for a {@link DtoBeanMeta}'s target -
+ * see {@code @DtoMapping(builder = ...)}.
+ * <p>
+ * Detected via the {@code avaje-recordbuilder}-style convention: a static no-arg
+ * {@code Target.builder()} factory method returning some builder type, which in turn has a
+ * fluent (returns-itself), same-named setter method per target property, plus a no-arg
+ * {@code build()} method returning the target type. When present (and either explicitly
+ * requested via {@code builder = ALWAYS}, or the target has more properties than the
+ * auto-detection threshold under {@code builder = AUTO}), the generated mapper constructs the
+ * target via {@code Target.builder().prop(x)....build()} instead of a positional constructor
+ * call.
+ */
+final class DtoBuilderMeta {
+
+  private final String builderTypeFullName;
+
+  DtoBuilderMeta(String builderTypeFullName) {
+    this.builderTypeFullName = builderTypeFullName;
+  }
+
+  String builderTypeFullName() {
+    return builderTypeFullName;
+  }
+
+  String builderTypeShortName() {
+    return Split.shortName(builderTypeFullName);
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoConverterMeta.java

@@ -0,0 +1,70 @@
+package io.ebean.querybean.generator;
+
+/**
+ * Metadata for a single {@code @DtoConvert(value = ConverterType.class, method = "name")}
+ * property conversion.
+ * <p>
+ * Dispatch strategy is decided purely by whether the referenced method is {@code static}:
+ * <ul>
+ *   <li>{@code static} - the generated mapper emits a direct static call
+ *   ({@code ConverterType.method(source.getX())}), no registration/constructor wiring needed at
+ *   all - for common, reusable, dependency-free conversions.</li>
+ *   <li>instance - the generated mapper resolves one shared instance via
+ *   {@code DtoConverterManager.get(ConverterType.class)}, wired as a constructor
+ *   parameter/field (same shape as nested-mapper constructor injection) - for conversions
+ *   needing a real dependency.</li>
+ * </ul>
+ */
+final class DtoConverterMeta {
+
+  private final String typeFullName;
+  private final String methodName;
+  private final boolean isStatic;
+
+  DtoConverterMeta(String typeFullName, String methodName, boolean isStatic) {
+    this.typeFullName = typeFullName;
+    this.methodName = methodName;
+    this.isStatic = isStatic;
+  }
+
+  String typeFullName() {
+    return typeFullName;
+  }
+
+  String typeShortName() {
+    return Split.shortName(typeFullName);
+  }
+
+  String methodName() {
+    return methodName;
+  }
+
+  boolean isStatic() {
+    return isStatic;
+  }
+
+  /**
+   * Field/parameter name used to hold the resolved instance for instance-dispatch conversions -
+   * derived from the converter type's short name, lower-camel-cased.
+   */
+  String fieldName() {
+    String name = typeShortName();
+    return Character.toLowerCase(name.charAt(0)) + name.substring(1);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof DtoConverterMeta)) {
+      return false;
+    }
+    return typeFullName.equals(((DtoConverterMeta) o).typeFullName);
+  }
+
+  @Override
+  public int hashCode() {
+    return typeFullName.hashCode();
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoMapperRegisterWriter.java

@@ -0,0 +1,274 @@
+package io.ebean.querybean.generator;
+
+import javax.tools.FileObject;
+import java.io.IOException;
+import java.io.Writer;
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Writes the per-module {@code DtoMapperRegister} implementation aggregating all generated DTO
+ * mappers, and registers it via {@code META-INF/services} - mirroring
+ * {@link SimpleModuleInfoWriter}'s {@code EbeanEntityRegister} mechanism. Dispatch is via
+ * literal {@code Class ==} comparisons only (no reflection/{@code Class.forName}), so this is
+ * the compile-time-safe backing for the {@code query.mapTo(SomeDto.class)} runtime API.
+ * <p>
+ * Each generated mapper is held as a single shared instance field on the register (mappers are
+ * stateless/thread-safe - only direct getter/constructor calls, no per-call state) rather than
+ * being constructed with {@code new} on every {@code mapperFor()} call - this avoids repeatedly
+ * rebuilding the nested mapper graph and {@code FetchGroup} on every {@code mapTo(...)} query.
+ * Fields are declared in dependency order (a mapper's nested mappers are declared, and so
+ * constructed, before it) so each field initializer can directly reference the already-built
+ * nested mapper fields it depends on.
+ */
+class DtoMapperRegisterWriter {
+
+  private static final String SHORT_NAME = "EbeanDtoMapperRegister";
+
+  private final ProcessingContext ctx;
+  private final List<DtoBeanMeta> metas;
+  private final List<DtoBeanMeta> sortedMetas;
+  private final String factoryPackage;
+  private final String factoryFullName;
+  private Append writer;
+
+  DtoMapperRegisterWriter(ProcessingContext ctx, List<DtoBeanMeta> metas) {
+    this.ctx = ctx;
+    this.metas = metas;
+    this.sortedMetas = sortByDependency(metas);
+    this.factoryPackage = shortestMapperPackage(metas);
+    this.factoryFullName = factoryPackage + "." + SHORT_NAME;
+  }
+
+  /**
+   * Order {@code metas} so that every mapper appears after all the (nested) mappers its own
+   * field initializer depends on - a dependency-first (topological) ordering over the
+   * {@code NESTED_ONE}/{@code NESTED_MANY} edges. Cross-reference cycles were already detected
+   * and excluded upstream in {@code DtoMappingReader}, so a simple DFS post-order is sufficient
+   * (the {@code visited} guard is defensive only).
+   */
+  private static List<DtoBeanMeta> sortByDependency(List<DtoBeanMeta> metas) {
+    List<DtoBeanMeta> sorted = new ArrayList<>(metas.size());
+    Set<DtoBeanMeta> visited = new HashSet<>();
+    for (DtoBeanMeta meta : metas) {
+      visitForSort(meta, visited, sorted);
+    }
+    return sorted;
+  }
+
+  private static void visitForSort(DtoBeanMeta meta, Set<DtoBeanMeta> visited, List<DtoBeanMeta> sorted) {
+    if (!visited.add(meta)) {
+      return;
+    }
+    for (DtoPropertyMeta property : meta.properties()) {
+      DtoBeanMeta nested = property.nested();
+      if (nested != null) {
+        visitForSort(nested, visited, sorted);
+      }
+    }
+    sorted.add(meta);
+  }
+
+  /**
+   * Shortest of the (per-pair) mapper packages, used as the single package the aggregating
+   * {@code EbeanDtoMapperRegister} is written to - mirrors {@code SimpleModuleInfoWriter}'s
+   * entity-package heuristic, but computed from the dto mapper packages themselves rather than
+   * {@code ProcessingContext.getFactoryPackage()} (which only tracks {@code @Entity} packages
+   * and is never populated during a test-source-only compilation round, which would otherwise
+   * make this fall back to its "unknown" default).
+   */
+  private static String shortestMapperPackage(List<DtoBeanMeta> metas) {
+    String shortest = null;
+    for (DtoBeanMeta meta : metas) {
+      String pkg = meta.mapperPackage();
+      if (shortest == null || pkg.length() < shortest.length()) {
+        shortest = pkg;
+      }
+    }
+    return shortest;
+  }
+
+  void write() throws IOException {
+    if (hasSimpleNameCollision()) {
+      return;
+    }
+    var javaFileObject = ctx.createWriter(factoryFullName);
+    writer = new Append(javaFileObject.openWriter());
+    writePackage();
+    writeClassStart();
+    writeFields();
+    writeMapperForMethod();
+    writeMapperOfTypeMethod();
+    writeClassEnd();
+    writer.close();
+    writeServicesFile();
+  }
+
+  /**
+   * Fail fast, with a clear diagnostic, if two different types referenced by the aggregated
+   * register (across every {@code @DtoMapping} pair in this module) share the same simple class
+   * name - dispatch and imports are both simple-name based (see {@link #writePackage()}), so an
+   * undetected collision would otherwise surface as a confusing duplicate-import compile error
+   * in the generated source rather than a clear message pointing at the actual cause.
+   */
+  private boolean hasSimpleNameCollision() {
+    Set<String> allReferenced = new LinkedHashSet<>();
+    for (DtoBeanMeta meta : metas) {
+      allReferenced.add(meta.sourceFullName());
+      allReferenced.add(meta.targetFullName());
+      allReferenced.add(meta.mapperFullName());
+      for (DtoConverterMeta converter : meta.converterDeps()) {
+        allReferenced.add(converter.typeFullName());
+      }
+    }
+    String[] collision = Split.findSimpleNameCollision(allReferenced);
+    if (collision != null) {
+      ctx.logError(null, "@DtoMapping simple name collision generating %s - %s and %s share the same"
+        + " simple class name; this is not currently supported within one module, use distinct class names",
+        SHORT_NAME, collision[0], collision[1]);
+      return true;
+    }
+    return false;
+  }
+
+  private void writePackage() {
+    writer.append("package %s;", factoryPackage).eol().eol();
+    Set<String> imports = new LinkedHashSet<>();
+    imports.add("io.ebean.DtoMapper");
+    imports.add("io.ebean.config.DtoMapperRegister");
+    for (DtoBeanMeta meta : metas) {
+      addImportIfNeeded(imports, meta.sourceFullName());
+      addImportIfNeeded(imports, meta.targetFullName());
+      addImportIfNeeded(imports, meta.mapperFullName());
+      for (DtoConverterMeta converter : meta.converterDeps()) {
+        addImportIfNeeded(imports, converter.typeFullName());
+      }
+      if (!meta.converterDeps().isEmpty()) {
+        imports.add("io.ebean.DtoConverterManager");
+      }
+    }
+    for (String imp : imports) {
+      writer.append("import %s;", imp).eol();
+    }
+    writer.eol();
+  }
+
+  private void addImportIfNeeded(Set<String> imports, String fullName) {
+    if (!Split.split(fullName)[0].equals(factoryPackage)) {
+      imports.add(fullName);
+    }
+  }
+
+  private void writeClassStart() {
+    writer.append(Constants.AT_GENERATED).eol();
+    writer.append("public class %s implements DtoMapperRegister {", SHORT_NAME).eol().eol();
+  }
+
+  /**
+   * Declare one field per generated mapper, in dependency order, each initialized exactly once -
+   * a single shared instance reused by every {@code mapperFor()} call rather than a new instance
+   * per call. A mapper with nested (ToOne/ToMany) properties and/or instance-dispatch
+   * {@code @DtoConvert} converters is constructed via its all-args constructor, passing the
+   * already-declared nested mapper fields and {@code DtoConverterManager.get(...)}-resolved
+   * converter instances it depends on.
+   */
+  private void writeFields() {
+    for (DtoBeanMeta meta : sortedMetas) {
+      List<DtoBeanMeta> deps = nestedMetas(meta);
+      List<DtoConverterMeta> converters = meta.converterDeps();
+      String shortName = meta.mapperShortName();
+      String fieldName = mapperFieldName(meta);
+      if (deps.isEmpty() && converters.isEmpty()) {
+        writer.append("  private final %s %s = new %s();", shortName, fieldName, shortName).eol();
+      } else {
+        StringBuilder args = new StringBuilder();
+        for (DtoBeanMeta dep : deps) {
+          if (args.length() > 0) {
+            args.append(", ");
+          }
+          args.append(mapperFieldName(dep));
+        }
+        for (DtoConverterMeta converter : converters) {
+          if (args.length() > 0) {
+            args.append(", ");
+          }
+          args.append("DtoConverterManager.get(").append(converter.typeShortName()).append(".class)");
+        }
+        writer.append("  private final %s %s = new %s(%s);", shortName, fieldName, shortName, args).eol();
+      }
+    }
+    writer.eol();
+  }
+
+  /**
+   * The other {@link DtoBeanMeta}s a mapper's all-args constructor depends on, in the same order
+   * {@link DtoMapperWriter} declares its nested mapper constructor parameters (declaration order
+   * of the target DTO's {@code NESTED_ONE}/{@code NESTED_MANY} properties).
+   */
+  private List<DtoBeanMeta> nestedMetas(DtoBeanMeta meta) {
+    List<DtoBeanMeta> nested = new ArrayList<>();
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (property.nested() != null) {
+        nested.add(property.nested());
+      }
+    }
+    return nested;
+  }
+
+  private String mapperFieldName(DtoBeanMeta meta) {
+    String name = meta.mapperShortName();
+    return Character.toLowerCase(name.charAt(0)) + name.substring(1);
+  }
+
+  private void writeMapperForMethod() {
+    writer.append("  @Override").eol();
+    writer.append("  @SuppressWarnings(\"unchecked\")").eol();
+    writer.append("  public <SOURCE, TARGET> DtoMapper<SOURCE, TARGET> mapperFor(Class<SOURCE> sourceType, Class<TARGET> targetType) {").eol();
+    for (DtoBeanMeta meta : metas) {
+      String sourceShort = Split.shortName(meta.sourceFullName());
+      String targetShort = Split.shortName(meta.targetFullName());
+      writer.append("    if (sourceType == %s.class && targetType == %s.class) return (DtoMapper<SOURCE, TARGET>) %s;",
+        sourceShort, targetShort, mapperFieldName(meta)).eol();
+    }
+    writer.append("    return null;").eol();
+    writer.append("  }").eol();
+  }
+
+  /**
+   * Look up a mapper instance by its own concrete generated type - e.g. {@code
+   * DtoMapperManager.get(CustomerDtoMapper.class)} - as an alternative to {@link
+   * #writeMapperForMethod()}'s (source, target) pair lookup, typically used to resolve a mapper
+   * instance for dependency injection into application code.
+   */
+  private void writeMapperOfTypeMethod() {
+    writer.eol();
+    writer.append("  @Override").eol();
+    writer.append("  @SuppressWarnings(\"unchecked\")").eol();
+    writer.append("  public <T> T mapperOfType(Class<T> mapperType) {").eol();
+    for (DtoBeanMeta meta : metas) {
+      writer.append("    if (mapperType == %s.class) return (T) %s;", meta.mapperShortName(), mapperFieldName(meta)).eol();
+    }
+    writer.append("    return null;").eol();
+    writer.append("  }").eol();
+  }
+
+  private void writeClassEnd() {
+    writer.append("}").eol();
+  }
+
+  private void writeServicesFile() {
+    try {
+      FileObject jfo = ctx.createMetaInfWriter(Constants.METAINF_SERVICES_DTOMAPPERREGISTER);
+      if (jfo != null) {
+        Writer w = jfo.openWriter();
+        w.write(factoryFullName);
+        w.close();
+      }
+    } catch (IOException e) {
+      ctx.logError(null, "Failed to write DtoMapperRegister services file " + e.getMessage());
+    }
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoMapperVariant.java

@@ -0,0 +1,62 @@
+package io.ebean.querybean.generator;
+
+import java.util.Set;
+
+/**
+ * A named variant of a {@link DtoBeanMeta} - see {@code @DtoMapping(name = "...", exclude =
+ * "...")}. Generated into the *same* mapper class as the base mapping (not a separate class),
+ * excluding one or more nested {@code ToOne}/{@code ToMany} properties from both its own
+ * {@code fetchGroup} and its mapped output.
+ * <p>
+ * Exposed on the generated mapper as a same-named accessor method returning its own
+ * {@code DtoMapper<SOURCE, TARGET>} view (a small inner class delegating back to the shared,
+ * once-written {@code build(...)} method) - e.g. {@code name = "noFleets"} generates a
+ * {@code noFleets()} method, so callers can do
+ * {@code query.mapTo(Target.class, mapper.noFleets())} with no string-based lookup.
+ */
+final class DtoMapperVariant {
+
+  private final String name;
+  private final String suffix;
+  private final Set<String> excludedProperties;
+
+  DtoMapperVariant(String name, Set<String> excludedProperties) {
+    this.name = name;
+    this.suffix = Character.toUpperCase(name.charAt(0)) + name.substring(1);
+    this.excludedProperties = excludedProperties;
+  }
+
+  /** The variant name as declared, e.g. {@code "noFleets"} - also the accessor method name. */
+  String name() {
+    return name;
+  }
+
+  /** {@link #name()} capitalized, e.g. {@code "NoFleets"} - used to derive generated identifiers. */
+  String suffix() {
+    return suffix;
+  }
+
+  /** Dto field names (of {@code NESTED_ONE}/{@code NESTED_MANY} properties) this variant excludes. */
+  Set<String> excludedProperties() {
+    return excludedProperties;
+  }
+
+  boolean excludes(DtoPropertyMeta property) {
+    return excludedProperties.contains(property.dtoFieldName());
+  }
+
+  /** Field name holding this variant's own {@code FetchGroup}, e.g. {@code fetchGroupNoFleets}. */
+  String fetchGroupFieldName() {
+    return "fetchGroup" + suffix;
+  }
+
+  /** Inner class name implementing {@code DtoMapper<SOURCE, TARGET>} for this variant. */
+  String innerClassName() {
+    return suffix + "Mapper";
+  }
+
+  /** Field name holding the (lazily unnecessary - eagerly built) inner mapper instance. */
+  String fieldName() {
+    return name + "View";
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoMapperWriter.java

@@ -0,0 +1,593 @@
+package io.ebean.querybean.generator;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Writes a single generated {@code XxxMapper.java} implementing {@code io.ebean.DtoMapper<S,T>}
+ * for one {@link DtoBeanMeta}, in the exact shape validated by the hand-written
+ * dto-spike-toone-mapper / dto-spike-tomany-identity spikes: no reflection, nested mappers wired
+ * via constructor injection (a no-arg constructor supplying default instances, plus an explicit
+ * overload for substitution in tests). Identity de-duplication via the shared
+ * {@code DtoMapContext}'s {@code computeIfAbsent} is only generated for types that are actually
+ * nested elsewhere in the DTO graph (see {@link DtoBeanMeta#nestedElsewhere()}) - a pure
+ * top-level type constructs its DTO directly, since the cache could never produce a hit for it.
+ */
+class DtoMapperWriter {
+
+  private final ProcessingContext ctx;
+  private final DtoBeanMeta meta;
+  private Append writer;
+
+  DtoMapperWriter(ProcessingContext ctx, DtoBeanMeta meta) {
+    this.ctx = ctx;
+    this.meta = meta;
+  }
+
+  void write() throws IOException {
+    if (hasSimpleNameCollision()) {
+      return;
+    }
+    var javaFileObject = ctx.createWriter(meta.mapperFullName(), meta.target());
+    writer = new Append(javaFileObject.openWriter());
+    writePackage();
+    writeImports();
+    writeClassStart();
+    writeConstructors();
+    writeFetchGroupMethod();
+    writeMapMethod();
+    if (!meta.variants().isEmpty()) {
+      writeBuildMethod();
+      writeVariantAccessors();
+    }
+    writeClassEnd();
+    writer.close();
+  }
+
+  /**
+   * Fail fast, with a clear diagnostic, if two different types referenced by this single
+   * generated mapper (source, target, any nested source/target/mapper, any converter type) share
+   * the same simple class name - {@link #writeImports()} relies on simple names being unambiguous
+   * within the file, so an undetected collision would otherwise surface as a confusing
+   * duplicate-import compile error rather than a clear message pointing at the actual cause.
+   */
+  private boolean hasSimpleNameCollision() {
+    Set<String> allReferenced = new LinkedHashSet<>();
+    allReferenced.add(meta.sourceFullName());
+    allReferenced.add(meta.targetFullName());
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (property.nested() != null) {
+        allReferenced.add(property.nested().sourceFullName());
+        allReferenced.add(property.nested().targetFullName());
+        allReferenced.add(property.nested().mapperFullName());
+      }
+      if (property.converter() != null) {
+        allReferenced.add(property.converter().typeFullName());
+      }
+    }
+    String[] collision = Split.findSimpleNameCollision(allReferenced);
+    if (collision != null) {
+      ctx.logError(meta.target(), "@DtoMapping simple name collision generating %s - %s and %s share the"
+        + " same simple class name; this is not currently supported within one generated mapper, use"
+        + " distinct class names", meta.mapperShortName(), collision[0], collision[1]);
+      return true;
+    }
+    return false;
+  }
+
+  private void writePackage() {
+    writer.append("package %s;", meta.mapperPackage()).eol().eol();
+  }
+
+  private void writeImports() {
+    Set<String> imports = new LinkedHashSet<>();
+    imports.add("io.ebean.DtoMapper");
+    imports.add("io.ebean.DtoMapContext");
+    imports.add("io.ebean.FetchGroup");
+    addImportIfNeeded(imports, meta.sourceFullName());
+    addImportIfNeeded(imports, meta.targetFullName());
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (property.nested() != null) {
+        addImportIfNeeded(imports, property.nested().sourceFullName());
+        addImportIfNeeded(imports, property.nested().targetFullName());
+        addImportIfNeeded(imports, property.nested().mapperFullName());
+      }
+      if (property.converter() != null) {
+        addImportIfNeeded(imports, property.converter().typeFullName());
+      }
+    }
+    if (!meta.converterDeps().isEmpty()) {
+      imports.add("io.ebean.DtoConverterManager");
+    }
+    if (variableProperties().stream().anyMatch(p -> p.kind() == DtoPropertyMeta.Kind.NESTED_MANY)) {
+      imports.add("java.util.List");
+    }
+    for (String imp : imports) {
+      writer.append("import %s;", imp).eol();
+    }
+    writer.eol();
+  }
+
+  private void addImportIfNeeded(Set<String> imports, String fullName) {
+    String pkg = Split.split(fullName)[0];
+    if (pkg != null && !pkg.equals(meta.mapperPackage())) {
+      imports.add(fullName);
+    }
+  }
+
+  private void writeClassStart() {
+    String sourceShort = Split.shortName(meta.sourceFullName());
+    String targetShort = Split.shortName(meta.targetFullName());
+    writer.append(Constants.AT_GENERATED).eol();
+    writer.append("public final class %s implements DtoMapper<%s, %s> {", meta.mapperShortName(),
+      sourceShort, targetShort).eol().eol();
+    for (DtoPropertyMeta property : nestedProperties()) {
+      writer.append("  private final DtoMapper<%s, %s> %s;",
+        Split.shortName(property.nested().sourceFullName()),
+        Split.shortName(property.nested().targetFullName()),
+        mapperFieldName(property)).eol();
+    }
+    for (DtoConverterMeta converter : meta.converterDeps()) {
+      writer.append("  private final %s %s;", converter.typeShortName(), converter.fieldName()).eol();
+    }
+    writer.append("  private final FetchGroup<%s> fetchGroup;", sourceShort).eol();
+    for (DtoMapperVariant variant : meta.variants()) {
+      writer.append("  private final FetchGroup<%s> %s;", sourceShort, variant.fetchGroupFieldName()).eol();
+    }
+    // one shared, stateless instance per variant - same "singleton, not `new` per call" approach
+    // DtoMapperRegisterWriter already uses for the top-level generated mappers themselves
+    for (DtoMapperVariant variant : meta.variants()) {
+      writer.append("  private final DtoMapper<%s, %s> %s;", sourceShort, targetShort, variant.fieldName()).eol();
+    }
+    writer.eol();
+  }
+
+  private void writeConstructors() {
+    var nested = nestedProperties();
+    var converters = meta.converterDeps();
+    if (nested.isEmpty() && converters.isEmpty()) {
+      writer.append("  public %s() {", meta.mapperShortName()).eol();
+      writeAllFetchGroupAssignments("    ");
+      writeAllVariantViewAssignments("    ");
+      writer.append("  }").eol().eol();
+      return;
+    }
+    writer.append("  public %s() {", meta.mapperShortName()).eol();
+    StringBuilder args = new StringBuilder();
+    for (DtoPropertyMeta property : nested) {
+      if (args.length() > 0) {
+        args.append(", ");
+      }
+      args.append("new ").append(property.nested().mapperShortName()).append("()");
+    }
+    for (DtoConverterMeta converter : converters) {
+      if (args.length() > 0) {
+        args.append(", ");
+      }
+      args.append("DtoConverterManager.get(").append(converter.typeShortName()).append(".class)");
+    }
+    writer.append("    this(%s);", args).eol();
+    writer.append("  }").eol().eol();
+
+    writer.append("  public %s(", meta.mapperShortName());
+    StringBuilder params = new StringBuilder();
+    for (DtoPropertyMeta property : nested) {
+      if (params.length() > 0) {
+        params.append(", ");
+      }
+      params.append("DtoMapper<").append(Split.shortName(property.nested().sourceFullName()))
+        .append(", ").append(Split.shortName(property.nested().targetFullName())).append("> ")
+        .append(mapperFieldName(property));
+    }
+    for (DtoConverterMeta converter : converters) {
+      if (params.length() > 0) {
+        params.append(", ");
+      }
+      params.append(converter.typeShortName()).append(" ").append(converter.fieldName());
+    }
+    writer.append("%s) {", params).eol();
+    for (DtoPropertyMeta property : nested) {
+      writer.append("    this.%s = %s;", mapperFieldName(property), mapperFieldName(property)).eol();
+    }
+    for (DtoConverterMeta converter : converters) {
+      writer.append("    this.%s = %s;", converter.fieldName(), converter.fieldName()).eol();
+    }
+    writeAllFetchGroupAssignments("    ");
+    writeAllVariantViewAssignments("    ");
+    writer.append("  }").eol().eol();
+  }
+
+  /**
+   * Build the list of {@code .select(...)}/{@code .fetch(...)} chain calls (without the leading
+   * dot) needed to populate the target DTO - derived from the DTO's declared shape rather than
+   * maintained by hand. {@code REF} properties (the {@code @DtoRef} id-only escape hatch) add
+   * their association's name to the root {@code select(...)} - this reads the FK column directly
+   * off the base table (no join, unlike {@code .fetch(assoc, "id")}) and, importantly, actually
+   * populates it rather than relying on it being "already there" (which only holds when some
+   * other property on this same DTO independently fetches that association). Skipped only when
+   * the same association is already fully fetched via a {@code NESTED_ONE}/{@code NESTED_MANY}
+   * property, to avoid a redundant/duplicate select of a path that's already covered by a fetch.
+   */
+  private List<String> fetchGroupChainCalls(Set<String> excludedFieldNames) {
+    List<DtoPropertyMeta> activeProperties = new ArrayList<>();
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (!excludedFieldNames.contains(property.dtoFieldName())) {
+        activeProperties.add(property);
+      }
+    }
+    Set<String> nestedAssocPaths = new LinkedHashSet<>();
+    for (DtoPropertyMeta property : activeProperties) {
+      if (property.kind() == DtoPropertyMeta.Kind.NESTED_ONE || property.kind() == DtoPropertyMeta.Kind.NESTED_MANY) {
+        nestedAssocPaths.add(property.sourcePropertyPath().get(0));
+      }
+    }
+    Set<String> rootSelect = new LinkedHashSet<>();
+    Map<String, List<String>> pathSelect = new LinkedHashMap<>();
+    List<String> fetchCalls = new ArrayList<>();
+    for (DtoPropertyMeta property : activeProperties) {
+      switch (property.kind()) {
+        case NESTED_ONE:
+        case NESTED_MANY:
+          fetchCalls.add(String.format("fetch(\"%s\", %s.fetchGroup())",
+            property.sourcePropertyPath().get(0), mapperFieldName(property)));
+          break;
+        case SCALAR:
+          List<String> path = property.sourcePropertyPath();
+          if (path.size() == 1) {
+            rootSelect.add(path.get(0));
+          } else {
+            String fetchPath = String.join(".", path.subList(0, path.size() - 1));
+            if (nestedAssocPaths.contains(fetchPath)) {
+              if (excludedFieldNames.isEmpty()) {
+                reportFetchPathCollision(property, fetchPath);
+              }
+              break;
+            }
+            pathSelect.computeIfAbsent(fetchPath, p -> new ArrayList<>())
+              .add(path.get(path.size() - 1));
+          }
+          break;
+        case REF:
+        default:
+          String assoc = property.sourcePropertyPath().get(0);
+          if (!nestedAssocPaths.contains(assoc)) {
+            rootSelect.add(assoc);
+          }
+          break;
+      }
+    }
+    for (var entry : pathSelect.entrySet()) {
+      fetchCalls.add(String.format("fetch(\"%s\", \"%s\")", entry.getKey(), String.join(",", entry.getValue())));
+    }
+    List<String> calls = new ArrayList<>();
+    if (!rootSelect.isEmpty()) {
+      calls.add(String.format("select(\"%s\")", String.join(",", rootSelect)));
+    }
+    calls.addAll(fetchCalls);
+    return calls;
+  }
+
+  /**
+   * Fail fast at codegen time rather than silently generating broken code: {@code OrmQueryDetail}
+   * keys its fetch paths by exact path string and {@code fetch(path, ...)} replaces (not merges)
+   * any existing entry for that same key - so a {@code @DtoPath} property whose fetch path is
+   * identical to an existing {@code NESTED_ONE}/{@code NESTED_MANY} property's own fetch path would
+   * silently overwrite (or be overwritten by) that nested fetch, discarding whichever call happens
+   * to be emitted first/last. Detected here instead so the failure is a clear compile-time error.
+   */
+  private void reportFetchPathCollision(DtoPropertyMeta property, String fetchPath) {
+    ctx.logError(meta.target(),
+      "@DtoPath property '%s' on %s resolves to fetch path '%s', which collides with the nested"
+        + " mapping already using that same fetch path - Ebean's fetch spec can only carry one set"
+        + " of properties per path, so one silently discards the other. Move '%s' onto the nested"
+        + " DTO type instead (its own mapper's fetchGroup already fetches path '%s'), or choose a"
+        + " @DtoPath that reaches into a different, non-colliding path.",
+      property.dtoFieldName(), meta.targetFullName(), fetchPath, property.dtoFieldName(), fetchPath);
+  }
+
+  /**
+   * Write the {@code this.fetchGroup = FetchGroup.of(Source.class)...build();} assignment (and
+   * one per named {@link DtoMapperVariant}, each skipping its own excluded properties from the
+   * fetch spec), with each chained {@code .select()}/{@code .fetch()}/{@code .build()} call on
+   * its own line for readability.
+   */
+  private void writeAllFetchGroupAssignments(String indent) {
+    writeFetchGroupAssignment(indent, "fetchGroup", Set.of());
+    for (DtoMapperVariant variant : meta.variants()) {
+      writeFetchGroupAssignment(indent, variant.fetchGroupFieldName(), variant.excludedProperties());
+    }
+  }
+
+  private void writeFetchGroupAssignment(String indent, String fieldName, Set<String> excludedFieldNames) {
+    writer.append("%sthis.%s = FetchGroup.of(%s.class)", indent, fieldName, Split.shortName(meta.sourceFullName()));
+    for (String call : fetchGroupChainCalls(excludedFieldNames)) {
+      writer.eol().append("%s  .%s", indent, call);
+    }
+    writer.eol().append("%s  .build();", indent).eol();
+  }
+
+  /**
+   * Assign each named variant's shared, stateless inner-class instance (its {@code DtoMapper}
+   * view) once, in the constructor - a single instance is reused across every call to the
+   * variant's accessor method (e.g. {@code noFleets()}), rather than allocating a fresh one per
+   * call, matching {@code DtoMapperRegisterWriter}'s "singleton, not {@code new} per call"
+   * approach for the top-level generated mappers themselves.
+   */
+  private void writeAllVariantViewAssignments(String indent) {
+    for (DtoMapperVariant variant : meta.variants()) {
+      writer.append("%sthis.%s = new %s();", indent, variant.fieldName(), variant.innerClassName()).eol();
+    }
+  }
+
+  private void writeFetchGroupMethod() {
+    writer.append("  @Override").eol();
+    writer.append("  public FetchGroup<%s> fetchGroup() {", Split.shortName(meta.sourceFullName())).eol();
+    writer.append("    return fetchGroup;").eol();
+    writer.append("  }").eol().eol();
+  }
+
+  private void writeMapMethod() {
+    String sourceShort = Split.shortName(meta.sourceFullName());
+    String targetShort = Split.shortName(meta.targetFullName());
+    Set<DtoPropertyMeta> variableProps = variableProperties();
+    writer.append("  @Override").eol();
+    writer.append("  public %s map(%s source, DtoMapContext context) {", targetShort, sourceShort).eol();
+    writer.append("    if (source == null) {").eol();
+    writer.append("      return null;").eol();
+    writer.append("    }").eol();
+    if (!variableProps.isEmpty()) {
+      // named variants exist - route construction through the shared build(...) method, this
+      // (base) mapping includes every variable property (each still evaluated inline, at its own
+      // declared position, inside build() - see buildCallArgs())
+      if (meta.nestedElsewhere()) {
+        writer.append("    // dedup using DtoMapContext, same %s instance can be reached via more than one path in the graph", sourceShort).eol();
+        writer.append("    return context.computeIfAbsent(%s.class, source, s -> build(s, context%s));",
+          targetShort, buildCallArgs(variableProps)).eol();
+      } else {
+        writer.append("    // DtoMapContext for nested mappers only").eol();
+        writer.append("    return build(source, context%s);", buildCallArgs(variableProps)).eol();
+      }
+    } else if (meta.nestedElsewhere()) {
+      writer.append("    // dedup using DtoMapContext, same %s instance can be reached via more than one path in the graph", sourceShort).eol();
+      writeConstructionExpression(
+        String.format("    return context.computeIfAbsent(%s.class, source, s -> ", targetShort),
+        "s", variableProps, ")");
+    } else if (nestedProperties().isEmpty()) {
+      writer.append("    // skip DtoMapContext, only ever a top-level mapping").eol();
+      writeConstructionExpression("    return ", "source", variableProps, "");
+    } else {
+      writer.append("    // DtoMapContext for nested mappers only").eol();
+      writeConstructionExpression("    return ", "source", variableProps, "");
+    }
+    writer.append("  }").eol();
+  }
+
+  /**
+   * Emit the target construction expression - either a positional constructor call or, when
+   * {@link DtoBeanMeta#builderMeta()} is present (see {@code @DtoMapping(builder = ...)}), a
+   * {@code Target.builder()....build()} fluent chain. {@code linePrefix} is written before the
+   * expression starts (e.g. {@code "    return "} or a {@code computeIfAbsent(...)} lambda
+   * opener); {@code wrapperClosing} is any additional closing needed for an enclosing call this
+   * expression is nested inside (e.g. {@code ")"} to close an enclosing
+   * {@code computeIfAbsent(...)} call, or {@code ""} for a plain {@code return}) - the trailing
+   * {@code ";"} is always added here. Every property - including ones in {@code variableProps} -
+   * is evaluated inline, in true {@link DtoBeanMeta#properties()} declared order; a variable
+   * property's expression is simply guarded by its {@code includeXxx} boolean parameter (see
+   * {@link #writeBuildMethod()}), so no property's evaluation is ever hoisted out of its declared
+   * position (only non-empty when named variants exist - see {@link #variableProperties()}).
+   */
+  private void writeConstructionExpression(String linePrefix, String rootVariable, Set<DtoPropertyMeta> variableProps, String wrapperClosing) {
+    String targetShort = Split.shortName(meta.targetFullName());
+    if (meta.builderMeta() == null) {
+      writer.append("%snew %s(", linePrefix, targetShort).eol();
+      writeConstructionArgs(rootVariable, variableProps, ")" + wrapperClosing + ";");
+    } else {
+      writer.append("%s%s.builder()", linePrefix, targetShort).eol();
+      writeBuilderChain(rootVariable, variableProps);
+      writer.append("      .build()%s;", wrapperClosing).eol();
+    }
+  }
+
+  private void writeConstructionArgs(String rootVariable, Set<DtoPropertyMeta> variableProps, String closing) {
+    var properties = meta.properties();
+    for (int i = 0; i < properties.size(); i++) {
+      DtoPropertyMeta property = properties.get(i);
+      writer.append("      %s%s", constructionValueExpression(property, rootVariable, variableProps),
+        i < properties.size() - 1 ? "," : closing).eol();
+    }
+    if (properties.isEmpty()) {
+      writer.append("      %s", closing).eol();
+    }
+  }
+
+  private void writeBuilderChain(String rootVariable, Set<DtoPropertyMeta> variableProps) {
+    for (DtoPropertyMeta property : meta.properties()) {
+      writer.append("      .%s(%s)", property.dtoFieldName(), constructionValueExpression(property, rootVariable, variableProps)).eol();
+    }
+  }
+
+  /**
+   * A variable property (excluded by at least one named variant) is guarded by its own
+   * {@code includeXxx} boolean parameter (see {@link #writeBuildMethod()}) - a ternary choosing
+   * between its real computed expression and its empty default - so it stays evaluated inline, at
+   * its true declared position, exactly like a non-variable property. This preserves the DTO's
+   * declared property order as the actual evaluation order, regardless of which properties happen
+   * to be excluded by a variant.
+   */
+  private String constructionValueExpression(DtoPropertyMeta property, String rootVariable, Set<DtoPropertyMeta> variableProps) {
+    String expression = propertyValueExpression(property, rootVariable);
+    return variableProps.contains(property)
+      ? includeFlagName(property) + " ? " + expression + " : " + defaultValueFor(property)
+      : expression;
+  }
+
+  /**
+   * The set of properties (in {@link DtoBeanMeta#properties()} order) excluded by at least one
+   * {@link DtoMapperVariant} - each becomes an extra {@code boolean includeXxx} parameter on the
+   * shared {@link #writeBuildMethod()} (rather than a precomputed value), so build() itself
+   * decides - at the property's own declared position - whether to compute it or substitute its
+   * empty default. Empty when {@link DtoBeanMeta#variants()} is empty.
+   */
+  private Set<DtoPropertyMeta> variableProperties() {
+    Set<DtoPropertyMeta> result = new LinkedHashSet<>();
+    for (DtoPropertyMeta property : meta.properties()) {
+      for (DtoMapperVariant variant : meta.variants()) {
+        if (variant.excludes(property)) {
+          result.add(property);
+          break;
+        }
+      }
+    }
+    return result;
+  }
+
+  /** {@code true} literal (comma-prefixed) per variable property - the base mapping includes every property. */
+  private String buildCallArgs(Set<DtoPropertyMeta> variableProps) {
+    StringBuilder sb = new StringBuilder();
+    for (DtoPropertyMeta property : variableProps) {
+      sb.append(", true");
+    }
+    return sb.toString();
+  }
+
+  /**
+   * The private construction helper shared by the base {@code map()} and every named variant -
+   * written once, so the common field population logic isn't duplicated per variant. Each
+   * variable property (see {@link #variableProperties()}) is accepted as a {@code boolean
+   * includeXxx} parameter rather than a precomputed value - build() evaluates every property
+   * inline, at its own declared position, choosing the real expression or the empty default based
+   * on the flag - so introducing variants never changes evaluation order relative to the DTO's
+   * declared property order.
+   */
+  private void writeBuildMethod() {
+    Set<DtoPropertyMeta> variableProps = variableProperties();
+    String sourceShort = Split.shortName(meta.sourceFullName());
+    String targetShort = Split.shortName(meta.targetFullName());
+    writer.append("  private %s build(%s source, DtoMapContext context%s) {",
+      targetShort, sourceShort, buildMethodParams(variableProps)).eol();
+    writeConstructionExpression("    return ", "source", variableProps, "");
+    writer.append("  }").eol().eol();
+  }
+
+  private String buildMethodParams(Set<DtoPropertyMeta> variableProps) {
+    StringBuilder sb = new StringBuilder();
+    for (DtoPropertyMeta property : variableProps) {
+      sb.append(", boolean ").append(includeFlagName(property));
+    }
+    return sb.toString();
+  }
+
+  /** Parameter/flag name for a variable property, e.g. {@code contacts} -> {@code includeContacts}. */
+  private String includeFlagName(DtoPropertyMeta property) {
+    String name = property.dtoFieldName();
+    return "include" + Character.toUpperCase(name.charAt(0)) + name.substring(1);
+  }
+
+  /**
+   * The empty/default value a variant supplies for a property it excludes - {@code null} for a
+   * {@code NESTED_ONE}, {@code List.of()} for a {@code NESTED_MANY} (always valid since
+   * {@code NESTED_MANY} only ever derives from a {@code java.util.List<X>} target property).
+   */
+  private String defaultValueFor(DtoPropertyMeta property) {
+    return property.kind() == DtoPropertyMeta.Kind.NESTED_MANY ? "List.of()" : "null";
+  }
+
+  /**
+   * Write each {@link DtoMapperVariant}'s public accessor method (returning its own
+   * {@code DtoMapper<SOURCE, TARGET>} view, e.g. {@code noFleets()}) followed by its small inner
+   * class delegating back to the shared {@link #writeBuildMethod()}. Deliberately skips the
+   * {@code DtoMapContext} identity-dedup wrapper used by the base mapping when
+   * {@link DtoBeanMeta#nestedElsewhere()} - named variants are only ever used as an independent,
+   * top-level {@code query.mapTo(...)} result, never nested inside another DTO graph.
+   */
+  private void writeVariantAccessors() {
+    Set<DtoPropertyMeta> variableProps = variableProperties();
+    String sourceShort = Split.shortName(meta.sourceFullName());
+    String targetShort = Split.shortName(meta.targetFullName());
+    for (DtoMapperVariant variant : meta.variants()) {
+      writer.append("  /** Named variant excluding {%s} - see @DtoMapping(name = \"%s\", exclude = ...). */",
+        String.join(", ", variant.excludedProperties()), variant.name()).eol();
+      writer.append("  public DtoMapper<%s, %s> %s() {", sourceShort, targetShort, variant.name()).eol();
+      writer.append("    return %s;", variant.fieldName()).eol();
+      writer.append("  }").eol().eol();
+    }
+    for (DtoMapperVariant variant : meta.variants()) {
+      writeVariantInnerClass(variant, variableProps, sourceShort, targetShort);
+    }
+  }
+
+  private void writeVariantInnerClass(DtoMapperVariant variant, Set<DtoPropertyMeta> variableProps, String sourceShort, String targetShort) {
+    writer.append("  private final class %s implements DtoMapper<%s, %s> {", variant.innerClassName(), sourceShort, targetShort).eol().eol();
+    writer.append("    @Override").eol();
+    writer.append("    public FetchGroup<%s> fetchGroup() {", sourceShort).eol();
+    writer.append("      return %s;", variant.fetchGroupFieldName()).eol();
+    writer.append("    }").eol().eol();
+    writer.append("    @Override").eol();
+    writer.append("    public %s map(%s source, DtoMapContext context) {", targetShort, sourceShort).eol();
+    writer.append("      if (source == null) {").eol();
+    writer.append("        return null;").eol();
+    writer.append("      }").eol();
+    writer.append("      return build(source, context%s);", variantBuildArgs(variant, variableProps)).eol();
+    writer.append("    }").eol();
+    writer.append("  }").eol().eol();
+  }
+
+  /** {@code true}/{@code false} literal (comma-prefixed) per variable property - {@code false} for ones this variant excludes. */
+  private String variantBuildArgs(DtoMapperVariant variant, Set<DtoPropertyMeta> variableProps) {
+    StringBuilder sb = new StringBuilder();
+    for (DtoPropertyMeta property : variableProps) {
+      sb.append(", ").append(!variant.excludes(property));
+    }
+    return sb.toString();
+  }
+  private String propertyValueExpression(DtoPropertyMeta property, String rootVariable) {
+    switch (property.kind()) {
+      case NESTED_ONE:
+        return mapperFieldName(property) + ".map(" + property.sourceValueExpression(rootVariable) + ", context)";
+      case NESTED_MANY:
+        return mapperFieldName(property) + ".mapList(" + property.sourceValueExpression(rootVariable) + ", context)";
+      case SCALAR:
+      case REF:
+      default:
+        return applyConverter(property, property.sourceValueExpression(rootVariable));
+    }
+  }
+
+  /**
+   * Wrap {@code rawExpression} in the property's {@code @DtoConvert} conversion call, if any -
+   * a direct static call ({@code ConverterType.method(rawExpression)}) or a call against the
+   * resolved instance field ({@code converterField.method(rawExpression)}) depending on
+   * {@link DtoConverterMeta#isStatic()}.
+   */
+  private String applyConverter(DtoPropertyMeta property, String rawExpression) {
+    DtoConverterMeta converter = property.converter();
+    if (converter == null) {
+      return rawExpression;
+    }
+    String receiver = converter.isStatic() ? converter.typeShortName() : converter.fieldName();
+    return receiver + "." + converter.methodName() + "(" + rawExpression + ")";
+  }
+
+  private List<DtoPropertyMeta> nestedProperties() {
+    List<DtoPropertyMeta> nested = new ArrayList<>();
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (property.nested() != null) {
+        nested.add(property);
+      }
+    }
+    return nested;
+  }
+
+  private String mapperFieldName(DtoPropertyMeta property) {
+    return property.dtoFieldName() + "Mapper";
+  }
+
+  private void writeClassEnd() {
+    writer.append("}").eol();
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoMappingReader.java

@@ -0,0 +1,714 @@
+package io.ebean.querybean.generator;
+
+import javax.annotation.processing.RoundEnvironment;
+import javax.lang.model.element.AnnotationMirror;
+import javax.lang.model.element.AnnotationValue;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.ElementKind;
+import javax.lang.model.element.ExecutableElement;
+import javax.lang.model.element.Modifier;
+import javax.lang.model.element.ModuleElement;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.element.VariableElement;
+import javax.lang.model.type.DeclaredType;
+import javax.lang.model.type.TypeKind;
+import javax.lang.model.type.TypeMirror;
+import javax.lang.model.util.ElementFilter;
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Reads all {@code @DtoMapping(source, target)} declarations present in the current round,
+ * builds a {@link DtoBeanMeta} (with matched properties) for each pair, and excludes any that
+ * take part in a cycle in the nested-DTO type graph (logging a clear error for each).
+ */
+class DtoMappingReader {
+
+  /** Auto-detection threshold for {@code @DtoMapping(builder = AUTO)} - see {@link #resolveBuilder}. */
+  private static final int BUILDER_AUTO_THRESHOLD = 5;
+
+  private final ProcessingContext ctx;
+  private final Map<String, DtoBeanMeta> byTargetName = new LinkedHashMap<>();
+
+  /**
+   * {@code @DtoMixin}-annotated companion types, keyed by the (qualified name of the) real DTO
+   * type they overlay annotations onto - see {@link #collectMixins(RoundEnvironment)}.
+   */
+  private final Map<String, TypeElement> mixinsByTarget = new LinkedHashMap<>();
+
+  /**
+   * Raw {@code @DtoMapping(name = "...", exclude = "...")} variant registrations, keyed by
+   * target FQN - resolved into {@link DtoMapperVariant}s (attached to the matching base
+   * {@link DtoBeanMeta}) once properties are known, in {@link #resolveVariants()}.
+   */
+  private final Map<String, List<RawVariant>> variantsByTarget = new LinkedHashMap<>();
+
+  /** {@code builder()} attribute value of each target's base (unnamed) registration. */
+  private final Map<String, String> builderModeByTarget = new LinkedHashMap<>();
+
+  private static final class RawVariant {
+    private final Element declaringElement;
+    private final TypeElement source;
+    private final String name;
+    private final List<String> exclude;
+
+    RawVariant(Element declaringElement, TypeElement source, String name, List<String> exclude) {
+      this.declaringElement = declaringElement;
+      this.source = source;
+      this.name = name;
+      this.exclude = exclude;
+    }
+
+    Element declaringElement() {
+      return declaringElement;
+    }
+
+    TypeElement source() {
+      return source;
+    }
+
+    String name() {
+      return name;
+    }
+
+    List<String> exclude() {
+      return exclude;
+    }
+  }
+
+  DtoMappingReader(ProcessingContext ctx) {
+    this.ctx = ctx;
+  }
+
+  /**
+   * Register all {@code @DtoMapping} pairs and {@code @DtoMixin} companion types found in this
+   * round (called once per processing round - both are typically only present in the first
+   * round, but later rounds may still contribute if generated sources declare them too).
+   */
+  void collect(RoundEnvironment roundEnv) {
+    Set<Element> elements = new LinkedHashSet<>();
+    addAnnotatedElements(roundEnv, Constants.DTO_MAPPING, elements);
+    // DtoMapping is @Repeatable - when used more than once on the same element javac wraps the
+    // repeated instances in a single synthetic container annotation (@DtoMapping.List) rather
+    // than repeating the plain annotation, so it must also be checked explicitly, and
+    // DtoMappingPrism doesn't unwrap that container for us - see allDtoMappingMirrors() below.
+    addAnnotatedElements(roundEnv, Constants.DTO_MAPPING_LIST, elements);
+    for (Element element : elements) {
+      for (AnnotationMirror mirror : allDtoMappingMirrors(element)) {
+        DtoMappingPrism prism = DtoMappingPrism.getInstance(mirror);
+        if (prism != null) {
+          register(element, prism);
+        }
+      }
+    }
+    collectMixins(roundEnv);
+  }
+
+  /**
+   * Discover {@code @DtoMixin(Target.class)} companion types (proactively, via {@code
+   * roundEnv.getElementsAnnotatedWith(...)} - unlike {@code @DtoPath}/{@code @DtoRef}/{@code
+   * @DtoConvert}, a mixin doesn't annotate an already-being-iterated field of a known {@code
+   * @DtoMapping} target, so it can't be discovered lazily from within {@link #resolveProperty}).
+   */
+  private void collectMixins(RoundEnvironment roundEnv) {
+    TypeElement annotationType = ctx.elementUtils().getTypeElement(Constants.DTO_MIXIN);
+    if (annotationType == null) {
+      return;
+    }
+    for (Element element : roundEnv.getElementsAnnotatedWith(annotationType)) {
+      DtoMixinPrism prism = DtoMixinPrism.getInstanceOn(element);
+      if (prism == null) {
+        continue;
+      }
+      if (element.getKind() != ElementKind.INTERFACE && element.getKind() != ElementKind.CLASS) {
+        ctx.logError(element, "@DtoMixin must be declared on an interface or class");
+        continue;
+      }
+      TypeElement target = asTypeElement(prism.value());
+      if (target == null) {
+        ctx.logError(element, "@DtoMixin value() must be a class type");
+        continue;
+      }
+      mixinsByTarget.put(target.getQualifiedName().toString(), (TypeElement) element);
+    }
+  }
+
+  private void addAnnotatedElements(RoundEnvironment roundEnv, String annotationTypeName, Set<Element> elements) {
+    TypeElement annotationType = ctx.elementUtils().getTypeElement(annotationTypeName);
+    if (annotationType != null) {
+      elements.addAll(roundEnv.getElementsAnnotatedWith(annotationType));
+    }
+  }
+
+  /**
+   * Return the {@code @DtoMapping} annotation mirrors directly present on {@code element},
+   * unwrapping the synthetic {@code @DtoMapping.List} container mirror (produced by javac when
+   * {@code @DtoMapping} is repeated on the same element) into its individual mirrors.
+   */
+  private List<AnnotationMirror> allDtoMappingMirrors(Element element) {
+    List<AnnotationMirror> result = new ArrayList<>();
+    for (AnnotationMirror mirror : element.getAnnotationMirrors()) {
+      String fqn = ((TypeElement) mirror.getAnnotationType().asElement()).getQualifiedName().toString();
+      if (Constants.DTO_MAPPING.equals(fqn)) {
+        result.add(mirror);
+      } else if (Constants.DTO_MAPPING_LIST.equals(fqn)) {
+        for (var entry : mirror.getElementValues().entrySet()) {
+          if ("value".contentEquals(entry.getKey().getSimpleName())) {
+            @SuppressWarnings("unchecked")
+            List<? extends AnnotationValue> nested = (List<? extends AnnotationValue>) entry.getValue().getValue();
+            for (AnnotationValue value : nested) {
+              result.add((AnnotationMirror) value.getValue());
+            }
+          }
+        }
+      }
+    }
+    return result;
+  }
+
+  /**
+   * Match properties and check for cycles across all pairs collected so far (call once, at the
+   * end of processing - i.e. {@code roundEnv.processingOver()}). Returns an empty list if no
+   * {@code @DtoMapping} pairs were ever collected.
+   */
+  List<DtoBeanMeta> resolveAndValidate() {
+    if (byTargetName.isEmpty()) {
+      return List.of();
+    }
+    for (DtoBeanMeta meta : byTargetName.values()) {
+      resolveProperties(meta);
+    }
+    resolveVariants();
+    for (DtoBeanMeta meta : byTargetName.values()) {
+      resolveBuilder(meta, builderModeByTarget.get(meta.targetFullName()));
+    }
+    List<DtoBeanMeta> result = excludeCycles();
+    markNestedElsewhere(result);
+    return result;
+  }
+
+  /**
+   * Attach each raw {@code @DtoMapping(name = ..., exclude = ...)} variant registration (see
+   * {@link #register}) to its base mapping's {@link DtoBeanMeta}, validating that a base exists,
+   * variant names are unique per target, the variant's source matches the base's source, and
+   * each excluded name resolves to a {@code NESTED_ONE}/{@code NESTED_MANY} property.
+   */
+  private void resolveVariants() {
+    for (var entry : variantsByTarget.entrySet()) {
+      String targetFqn = entry.getKey();
+      DtoBeanMeta meta = byTargetName.get(targetFqn);
+      if (meta == null) {
+        ctx.logError(entry.getValue().get(0).declaringElement(),
+          "@DtoMapping variant(s) declared for target %s but no base @DtoMapping (without name())"
+            + " was found - declare one first", targetFqn);
+        continue;
+      }
+      Set<String> seenNames = new LinkedHashSet<>();
+      for (RawVariant raw : entry.getValue()) {
+        if (!seenNames.add(raw.name())) {
+          ctx.logError(raw.declaringElement(), "Duplicate @DtoMapping variant name \"%s\" for target %s",
+            raw.name(), targetFqn);
+          continue;
+        }
+        if (raw.source() != meta.source()) {
+          ctx.logError(raw.declaringElement(),
+            "@DtoMapping(name = \"%s\") variant's source (%s) must match the base mapping's source"
+              + " (%s) for target %s", raw.name(), raw.source().getQualifiedName(), meta.sourceFullName(), targetFqn);
+          continue;
+        }
+        Set<String> excluded = resolveExcludedProperties(meta, raw);
+        if (excluded != null) {
+          meta.addVariant(new DtoMapperVariant(raw.name(), excluded));
+        }
+      }
+    }
+  }
+
+  /**
+   * Validate and resolve one variant's {@code exclude()} property names against {@code meta}'s
+   * already-resolved properties - only {@code NESTED_ONE}/{@code NESTED_MANY} properties can be
+   * excluded (there's no type-safe "absent" value for an arbitrary scalar type). Returns
+   * {@code null} (with error(s) already logged) if anything doesn't resolve.
+   */
+  private Set<String> resolveExcludedProperties(DtoBeanMeta meta, RawVariant raw) {
+    if (raw.exclude().isEmpty()) {
+      ctx.logError(raw.declaringElement(), "@DtoMapping(name = \"%s\") on target %s must exclude() at"
+        + " least one nested ToOne/ToMany property", raw.name(), meta.targetFullName());
+      return null;
+    }
+    Set<String> result = new LinkedHashSet<>();
+    boolean ok = true;
+    for (String propName : raw.exclude()) {
+      DtoPropertyMeta property = findProperty(meta, propName);
+      if (property == null) {
+        ctx.logError(raw.declaringElement(), "@DtoMapping(name = \"%s\") exclude(\"%s\") does not match"
+          + " any property on target %s", raw.name(), propName, meta.targetFullName());
+        ok = false;
+      } else if (property.kind() != DtoPropertyMeta.Kind.NESTED_ONE && property.kind() != DtoPropertyMeta.Kind.NESTED_MANY) {
+        ctx.logError(raw.declaringElement(), "@DtoMapping(name = \"%s\") exclude(\"%s\") on target %s is"
+          + " not a nested ToOne/ToMany DTO property - only nested properties can be excluded (there's"
+          + " no type-safe \"absent\" value for an arbitrary scalar type)", raw.name(), propName, meta.targetFullName());
+        ok = false;
+      } else {
+        result.add(propName);
+      }
+    }
+    return ok ? result : null;
+  }
+
+  private DtoPropertyMeta findProperty(DtoBeanMeta meta, String name) {
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (property.dtoFieldName().equals(name)) {
+        return property;
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Decide (and, if applicable, detect) the builder-based construction path for {@code meta} -
+   * see {@code @DtoMapping(builder = ...)} and {@link DtoBuilderMeta}. {@code NEVER} always uses
+   * a positional constructor. {@code ALWAYS} requires a matching builder to be found (a codegen
+   * error otherwise). {@code AUTO} (the default) silently falls back to a positional constructor
+   * if no matching builder is found, and only actually uses one it does find once the target has
+   * more than {@link #BUILDER_AUTO_THRESHOLD} properties.
+   */
+  private void resolveBuilder(DtoBeanMeta meta, String builderMode) {
+    String mode = (builderMode == null || builderMode.isEmpty()) ? "AUTO" : builderMode;
+    if ("NEVER".equals(mode)) {
+      return;
+    }
+    boolean required = "ALWAYS".equals(mode);
+    DtoBuilderMeta builder = detectBuilder(meta, required);
+    if (builder != null && (required || meta.properties().size() > BUILDER_AUTO_THRESHOLD)) {
+      meta.builderMeta(builder);
+    }
+  }
+
+  /**
+   * Detect an {@code avaje-recordbuilder}-style builder on {@code meta.target()}: a static no-arg
+   * {@code builder()} method, whose return type has a no-arg {@code build()} method returning the
+   * target type, plus a fluent (returns-itself) same-named setter method for every one of
+   * {@code meta}'s properties. Returns {@code null} if any part of that shape is missing - logging
+   * a codegen error only when {@code required} (i.e. {@code builder = ALWAYS}); silent otherwise
+   * (i.e. {@code builder = AUTO}, where a missing builder just means "use a constructor instead").
+   */
+  private DtoBuilderMeta detectBuilder(DtoBeanMeta meta, boolean required) {
+    TypeElement target = meta.target();
+    ExecutableElement builderFactory = findStaticNoArgMethod(target, "builder");
+    if (builderFactory == null) {
+      if (required) {
+        ctx.logError(target, "@DtoMapping(builder = ALWAYS) on target %s but no static no-arg"
+          + " builder() method was found", meta.targetFullName());
+      }
+      return null;
+    }
+    TypeElement builderType = asTypeElement(builderFactory.getReturnType());
+    if (builderType == null) {
+      if (required) {
+        ctx.logError(target, "@DtoMapping(builder = ALWAYS) on target %s but builder() does not"
+          + " return a class type", meta.targetFullName());
+      }
+      return null;
+    }
+    ExecutableElement buildMethod = findMethod(builderType, "build");
+    if (buildMethod == null || !sameType(buildMethod.getReturnType(), target)) {
+      if (required) {
+        ctx.logError(target, "@DtoMapping(builder = ALWAYS) on target %s but %s has no build()"
+          + " method returning %s", meta.targetFullName(), builderType.getQualifiedName(), meta.targetFullName());
+      }
+      return null;
+    }
+    for (DtoPropertyMeta property : meta.properties()) {
+      if (findFluentSetter(builderType, property.dtoFieldName()) == null) {
+        if (required) {
+          ctx.logError(target, "@DtoMapping(builder = ALWAYS) on target %s but %s has no fluent"
+            + " \"%s(...)\" method", meta.targetFullName(), builderType.getQualifiedName(), property.dtoFieldName());
+        }
+        return null;
+      }
+    }
+    return new DtoBuilderMeta(builderType.getQualifiedName().toString());
+  }
+
+  private ExecutableElement findStaticNoArgMethod(TypeElement type, String name) {
+    for (ExecutableElement method : ElementFilter.methodsIn(type.getEnclosedElements())) {
+      if (method.getSimpleName().contentEquals(name) && method.getModifiers().contains(Modifier.STATIC)
+        && method.getParameters().isEmpty()) {
+        return method;
+      }
+    }
+    return null;
+  }
+
+  private ExecutableElement findFluentSetter(TypeElement builderType, String propertyName) {
+    for (ExecutableElement method : ElementFilter.methodsIn(builderType.getEnclosedElements())) {
+      if (method.getSimpleName().contentEquals(propertyName) && method.getParameters().size() == 1
+        && sameType(method.getReturnType(), builderType)) {
+        return method;
+      }
+    }
+    return null;
+  }
+
+  private boolean sameType(TypeMirror mirror, TypeElement expected) {
+    TypeElement actual = asTypeElement(mirror);
+    return actual != null && actual.getQualifiedName().contentEquals(expected.getQualifiedName());
+  }
+
+  /**
+   * Mark every {@link DtoBeanMeta} that's used as a {@code NESTED_ONE}/{@code NESTED_MANY}
+   * property by some other mapper in {@code metas} - see {@link DtoBeanMeta#nestedElsewhere()}.
+   */
+  private void markNestedElsewhere(List<DtoBeanMeta> metas) {
+    for (DtoBeanMeta meta : metas) {
+      for (DtoPropertyMeta property : meta.properties()) {
+        DtoBeanMeta nested = property.nested();
+        if (nested != null) {
+          nested.markNestedElsewhere();
+        }
+      }
+    }
+  }
+
+  private void register(Element declaringElement, DtoMappingPrism prism) {
+    TypeElement sourceType = asTypeElement(prism.source());
+    TypeElement targetType = asTypeElement(prism.target());
+    if (sourceType == null || targetType == null) {
+      ctx.logError(declaringElement, "@DtoMapping source/target must be class types");
+      return;
+    }
+    String targetFqn = targetType.getQualifiedName().toString();
+    String name = prism.name() == null ? "" : prism.name().trim();
+    if (name.isEmpty()) {
+      if (byTargetName.containsKey(targetFqn)) {
+        ctx.logError(declaringElement, "Duplicate base @DtoMapping for target %s - only one base"
+          + " (unnamed) mapping is allowed per target, use name() for additional variants", targetFqn);
+        return;
+      }
+      String mapperPackage = resolveMapperPackage(prism, targetType, declaringElement);
+      byTargetName.put(targetFqn, new DtoBeanMeta(sourceType, targetType, mapperPackage));
+      builderModeByTarget.put(targetFqn, prism.builder());
+    } else {
+      variantsByTarget.computeIfAbsent(targetFqn, t -> new ArrayList<>())
+        .add(new RawVariant(declaringElement, sourceType, name, prism.exclude()));
+    }
+  }
+
+  private TypeElement asTypeElement(TypeMirror mirror) {
+    if (mirror == null || mirror.getKind() != TypeKind.DECLARED) {
+      return null;
+    }
+    return (TypeElement) ((DeclaredType) mirror).asElement();
+  }
+
+  /**
+   * Resolve the package the generated mapper for {@code target} lives in: an explicit
+   * {@code mapperPackage()} override always wins; otherwise the target DTO's own package is
+   * reused, unless the DTO belongs to a different (named) Java module than the one declaring
+   * the {@code @DtoMapping}, in which case reusing it would be a JPMS split-package violation -
+   * in that case a package derived from the declaring module's own name is used instead
+   * (mirroring {@code LookupWriter}'s module-name-derived package fallback).
+   */
+  private String resolveMapperPackage(DtoMappingPrism prism, TypeElement target, Element declaringElement) {
+    String override = prism.mapperPackage();
+    if (override != null && !override.isEmpty()) {
+      return override;
+    }
+    ModuleElement targetModule = ctx.elementUtils().getModuleOf(target);
+    ModuleElement declaringModule = ctx.elementUtils().getModuleOf(declaringElement);
+    if (targetModule == null || declaringModule == null
+      || targetModule.isUnnamed() || declaringModule.isUnnamed()
+      || targetModule.getQualifiedName().contentEquals(declaringModule.getQualifiedName())) {
+      return Split.split(target.getQualifiedName().toString())[0];
+    }
+    return declaringModule.getQualifiedName() + ".dto";
+  }
+
+  private void resolveProperties(DtoBeanMeta meta) {
+    for (VariableElement field : ElementFilter.fieldsIn(meta.target().getEnclosedElements())) {
+      if (field.getModifiers().contains(Modifier.STATIC)) {
+        continue;
+      }
+      meta.addProperty(resolveProperty(field, meta));
+    }
+  }
+
+  private DtoPropertyMeta resolveProperty(VariableElement field, DtoBeanMeta meta) {
+    String name = field.getSimpleName().toString();
+    DtoConverterMeta converter = resolveConverter(field, meta);
+    DtoRefPrism refPrism = prismOn(field, meta, DtoRefPrism::getInstanceOn);
+    if (refPrism != null) {
+      String assocName = (name.endsWith("Id") && name.length() > 2) ? name.substring(0, name.length() - 2) : name;
+      String assocGetter = getterName(meta.source(), assocName);
+      TypeElement assocType = getterReturnType(meta.source(), assocGetter);
+      String idGetter = getterName(assocType, "id");
+      return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.REF, List.of(assocGetter, idGetter), List.of(assocName, "id"), null, converter);
+    }
+    DtoPathPrism pathPrism = prismOn(field, meta, DtoPathPrism::getInstanceOn);
+    if (pathPrism != null) {
+      List<String> getters = new ArrayList<>();
+      List<String> properties = new ArrayList<>();
+      TypeElement currentType = meta.source();
+      for (String segment : pathPrism.value().split("\\.")) {
+        String getter = getterName(currentType, segment);
+        getters.add(getter);
+        properties.add(segment);
+        currentType = currentType != null ? getterReturnType(currentType, getter) : null;
+      }
+      // a single-hop @DtoPath rename (e.g. @DtoPath("eboxStatus") on a field named "status")
+      // can still target a type with its own registered @DtoMapping - detect that the same way
+      // the plain (non-@DtoPath) branches below do, rather than always falling back to a raw
+      // scalar getter call that would fail to compile with a type mismatch against the nested
+      // DTO type. Multi-hop paths keep the existing scalar/flattening behaviour since fetch spec
+      // derivation for NESTED_ONE/MANY only supports a single association name.
+      if (properties.size() == 1) {
+        TypeMirror fieldType = field.asType();
+        TypeMirror listElementType = listElementType(fieldType);
+        if (listElementType != null) {
+          DtoBeanMeta nested = lookupByTarget(listElementType);
+          if (nested != null) {
+            return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_MANY, getters, properties, nested);
+          }
+        } else {
+          DtoBeanMeta nested = lookupByTarget(fieldType);
+          if (nested != null) {
+            return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_ONE, getters, properties, nested);
+          }
+        }
+      }
+      return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.SCALAR, getters, properties, null, converter);
+    }
+    TypeMirror fieldType = field.asType();
+    TypeMirror listElementType = listElementType(fieldType);
+    if (listElementType != null) {
+      DtoBeanMeta nested = lookupByTarget(listElementType);
+      if (nested != null) {
+        return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_MANY, List.of(getterName(meta.source(), name)), List.of(name), nested);
+      }
+    } else {
+      DtoBeanMeta nested = lookupByTarget(fieldType);
+      if (nested != null) {
+        return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_ONE, List.of(getterName(meta.source(), name)), List.of(name), nested);
+      }
+    }
+    return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.SCALAR, List.of(getterName(meta.source(), name)), List.of(name), null, converter);
+  }
+
+  /**
+   * Resolve a prism instance for {@code field}, falling back to the corresponding
+   * {@code @DtoMixin} companion method (same simple name) when {@code field} carries no such
+   * annotation directly and {@code meta.target()} has a registered mixin - this is what lets
+   * {@code @DtoPath}/{@code @DtoRef}/{@code @DtoConvert} be declared on a mixin instead of the
+   * (possibly generated/unowned) DTO type itself.
+   */
+  private <A> A prismOn(VariableElement field, DtoBeanMeta meta, java.util.function.Function<Element, A> lookup) {
+    A direct = lookup.apply(field);
+    if (direct != null) {
+      return direct;
+    }
+    ExecutableElement mixinMethod = findMixinMethod(meta, field.getSimpleName().toString());
+    return mixinMethod == null ? null : lookup.apply(mixinMethod);
+  }
+
+  /**
+   * The method on {@code meta.target()}'s registered {@code @DtoMixin} companion (if any) whose
+   * name matches {@code propertyName}, or {@code null} if no mixin is registered for this target
+   * or it declares no matching method.
+   */
+  private ExecutableElement findMixinMethod(DtoBeanMeta meta, String propertyName) {
+    TypeElement mixin = mixinsByTarget.get(meta.target().getQualifiedName().toString());
+    return mixin == null ? null : findMethod(mixin, propertyName);
+  }
+
+  /**
+   * Resolve the {@code @DtoConvert} conversion declared on {@code field} (or, failing that, its
+   * {@code @DtoMixin} companion method - see {@link #prismOn}), if any - determining
+   * static-vs-instance dispatch by locating the named method on the converter type. Returns
+   * {@code null} (with no error) if {@code @DtoConvert} isn't present at all.
+   */
+  private DtoConverterMeta resolveConverter(VariableElement field, DtoBeanMeta meta) {
+    DtoConvertPrism prism = prismOn(field, meta, DtoConvertPrism::getInstanceOn);
+    if (prism == null) {
+      return null;
+    }
+    TypeElement converterType = asTypeElement(prism.value());
+    if (converterType == null) {
+      ctx.logError(field, "@DtoConvert value() must be a class type");
+      return null;
+    }
+    String methodName = prism.method();
+    ExecutableElement method = findMethod(converterType, methodName);
+    if (method == null) {
+      ctx.logError(field, "@DtoConvert method \"%s\" not found on %s", methodName, converterType.getQualifiedName());
+      return null;
+    }
+    boolean isStatic = method.getModifiers().contains(Modifier.STATIC);
+    return new DtoConverterMeta(converterType.getQualifiedName().toString(), methodName, isStatic);
+  }
+
+  private ExecutableElement findMethod(TypeElement type, String methodName) {
+    for (ExecutableElement method : ElementFilter.methodsIn(type.getEnclosedElements())) {
+      if (method.getSimpleName().contentEquals(methodName)) {
+        return method;
+      }
+    }
+    return null;
+  }
+
+  private DtoBeanMeta lookupByTarget(TypeMirror type) {
+    TypeElement element = asTypeElement(type);
+    return element == null ? null : byTargetName.get(element.getQualifiedName().toString());
+  }
+
+  /**
+   * Return the {@code java.util.List} element type of {@code type}, or {@code null} if it isn't
+   * a (raw or parameterized) {@code java.util.List}.
+   */
+  private TypeMirror listElementType(TypeMirror type) {
+    if (type.getKind() != TypeKind.DECLARED) {
+      return null;
+    }
+    DeclaredType declaredType = (DeclaredType) type;
+    TypeElement typeElement = (TypeElement) declaredType.asElement();
+    if (!typeElement.getQualifiedName().contentEquals("java.util.List")) {
+      return null;
+    }
+    List<? extends TypeMirror> typeArguments = declaredType.getTypeArguments();
+    return typeArguments.isEmpty() ? null : typeArguments.get(0);
+  }
+
+  /**
+   * Resolve the accessor method name for {@code propertyName} on {@code type} (searching
+   * {@code type} and its superclass chain) by checking, in order, which shape actually exists as
+   * a real no-arg method: (1) {@code isXxx()} returning {@code boolean} (standard JavaBean
+   * convention for a primitive boolean accessor), (2) {@code getXxx()} (standard JavaBean
+   * convention), (3) the bare {@code propertyName()} itself - a "record-style" accessor, which
+   * isn't limited to an actual {@code record} type (Ebean does support record entity beans, but
+   * an ordinary class can just as easily expose bare/fluent-style accessors with no {@code get}/
+   * {@code is} prefix at all). Falls back to the guessed {@code getXxx()} name if {@code type} is
+   * {@code null} (unresolvable, e.g. a later {@code @DtoPath} segment whose receiver type
+   * couldn't be determined) or none of the three shapes actually exist.
+   */
+  private String getterName(TypeElement type, String propertyName) {
+    String capitalized = Character.toUpperCase(propertyName.charAt(0)) + propertyName.substring(1);
+    String isName = "is" + capitalized;
+    String getName = "get" + capitalized;
+    if (type == null) {
+      return getName;
+    }
+    if (hasNoArgMethod(type, isName, TypeKind.BOOLEAN)) {
+      return isName;
+    }
+    if (hasNoArgMethod(type, getName, null)) {
+      return getName;
+    }
+    if (hasNoArgMethod(type, propertyName, null)) {
+      return propertyName;
+    }
+    return getName;
+  }
+
+  /**
+   * Whether a no-arg method named {@code methodName} exists on {@code type} (searching
+   * {@code type} and its superclass chain), optionally constrained to a specific return
+   * {@code TypeKind} (e.g. {@code TypeKind.BOOLEAN} for a primitive boolean accessor) - pass
+   * {@code null} to accept any return type.
+   */
+  private boolean hasNoArgMethod(TypeElement type, String methodName, TypeKind returnKind) {
+    for (TypeElement current = type; current != null; current = superclassOf(current)) {
+      for (ExecutableElement method : ElementFilter.methodsIn(current.getEnclosedElements())) {
+        if (method.getParameters().isEmpty() && method.getSimpleName().contentEquals(methodName)
+          && (returnKind == null || method.getReturnType().getKind() == returnKind)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  /**
+   * The return type of the no-arg method {@code getterMethodName} resolved on {@code type}
+   * (searching {@code type} and its superclass chain) - used to walk each successive segment of
+   * a multi-segment {@code @DtoPath} through the actual intermediate types, so each segment's
+   * own accessor name can be resolved correctly against its real receiver type (e.g. a
+   * {@code boolean} property partway through the path). Returns {@code null} if unresolvable, in
+   * which case later segments fall back to the guessed {@code getXxx()} name.
+   */
+  private TypeElement getterReturnType(TypeElement type, String getterMethodName) {
+    for (TypeElement current = type; current != null; current = superclassOf(current)) {
+      for (ExecutableElement method : ElementFilter.methodsIn(current.getEnclosedElements())) {
+        if (method.getParameters().isEmpty() && method.getSimpleName().contentEquals(getterMethodName)) {
+          return asTypeElement(method.getReturnType());
+        }
+      }
+    }
+    return null;
+  }
+
+  private TypeElement superclassOf(TypeElement type) {
+    return asTypeElement(type.getSuperclass());
+  }
+
+  /**
+   * DFS-based cycle detection over the nested-DTO type graph (edges are {@code NESTED_ONE}/
+   * {@code NESTED_MANY} properties only - {@code REF}/{@code SCALAR} properties don't recurse
+   * into another mapper, so they can't participate in a cycle). Any {@link DtoBeanMeta} that
+   * takes part in a detected cycle is logged as an error and excluded from the returned list.
+   */
+  private List<DtoBeanMeta> excludeCycles() {
+    List<DtoBeanMeta> result = new ArrayList<>();
+    java.util.Set<DtoBeanMeta> cyclic = new java.util.HashSet<>();
+    for (DtoBeanMeta meta : byTargetName.values()) {
+      if (meta.visit == DtoBeanMeta.Visit.WHITE) {
+        detectCycle(meta, new ArrayDeque<>(), cyclic);
+      }
+    }
+    for (DtoBeanMeta meta : byTargetName.values()) {
+      if (!cyclic.contains(meta)) {
+        result.add(meta);
+      }
+    }
+    return result;
+  }
+
+  private void detectCycle(DtoBeanMeta meta, Deque<DtoBeanMeta> path, java.util.Set<DtoBeanMeta> cyclic) {
+    meta.visit = DtoBeanMeta.Visit.GRAY;
+    path.push(meta);
+    for (DtoPropertyMeta property : meta.properties()) {
+      DtoBeanMeta nested = property.nested();
+      if (nested == null) {
+        continue;
+      }
+      if (nested.visit == DtoBeanMeta.Visit.GRAY) {
+        reportCycle(path, nested, cyclic);
+      } else if (nested.visit == DtoBeanMeta.Visit.WHITE) {
+        detectCycle(nested, path, cyclic);
+      }
+    }
+    path.pop();
+    meta.visit = DtoBeanMeta.Visit.BLACK;
+  }
+
+  private void reportCycle(Deque<DtoBeanMeta> path, DtoBeanMeta cycleStart, java.util.Set<DtoBeanMeta> cyclic) {
+    StringBuilder chain = new StringBuilder(cycleStart.targetFullName());
+    for (DtoBeanMeta onPath : path) {
+      chain.insert(0, onPath.targetFullName() + " -> ");
+      cyclic.add(onPath);
+      if (onPath == cycleStart) {
+        break;
+      }
+    }
+    cyclic.add(cycleStart);
+    ctx.logError(cycleStart.target(),
+      "@DtoMapping cycle detected, not generating mappers for: %s -> %s "
+        + "(introduce a separate shallow DTO type, or an @DtoRef id-only field, to break the cycle)",
+      chain, cycleStart.targetFullName());
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/DtoPropertyMeta.java

@@ -0,0 +1,107 @@
+package io.ebean.querybean.generator;
+
+import java.util.List;
+
+/**
+ * Metadata for a single target DTO property (constructor argument), describing how its value is
+ * obtained from the source entity.
+ */
+class DtoPropertyMeta {
+
+  enum Kind {
+    /** Direct (or {@code @DtoPath}) scalar getter chain on the source, e.g. {@code s.getName()}. */
+    SCALAR,
+    /** {@code @DtoRef} id-only shortcut, e.g. {@code s.getCustomer().getId()}. */
+    REF,
+    /** Nested ToOne - delegates to another generated mapper. */
+    NESTED_ONE,
+    /** Nested ToMany - delegates to another generated mapper's {@code mapList}. */
+    NESTED_MANY
+  }
+
+  private final String dtoFieldName;
+  private final Kind kind;
+  private final List<String> sourceGetterPath;
+  private final List<String> sourcePropertyPath;
+  private final DtoBeanMeta nested;
+  private final DtoConverterMeta converter;
+
+  DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath, DtoBeanMeta nested) {
+    this(dtoFieldName, kind, sourceGetterPath, sourcePropertyPath, nested, null);
+  }
+
+  DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath, DtoBeanMeta nested, DtoConverterMeta converter) {
+    this.dtoFieldName = dtoFieldName;
+    this.kind = kind;
+    this.sourceGetterPath = sourceGetterPath;
+    this.sourcePropertyPath = sourcePropertyPath;
+    this.nested = nested;
+    this.converter = converter;
+  }
+
+  String dtoFieldName() {
+    return dtoFieldName;
+  }
+
+  Kind kind() {
+    return kind;
+  }
+
+  List<String> sourceGetterPath() {
+    return sourceGetterPath;
+  }
+
+  /**
+   * The literal Ebean bean-property name for each hop of {@link #sourceGetterPath()} (e.g.
+   * {@code ["billingAddress", "line1"]}) - kept separately from the getter-call path since the
+   * two diverge for accessor styles other than a plain {@code getXxx()}/{@code isXxx()} JavaBean
+   * getter (record-style bare accessors, boolean {@code isXxx()} accessors). Used to build
+   * {@code FetchGroup.select(...)}/{@code .fetch(...)} property strings without having to
+   * reverse-parse an accessor method name back into a property name.
+   */
+  List<String> sourcePropertyPath() {
+    return sourcePropertyPath;
+  }
+
+  /**
+   * The other {@link DtoBeanMeta} this property delegates to, for {@link Kind#NESTED_ONE} and
+   * {@link Kind#NESTED_MANY} properties. {@code null} otherwise.
+   */
+  DtoBeanMeta nested() {
+    return nested;
+  }
+
+  /**
+   * The {@code @DtoConvert} conversion to apply to this property's raw source value, or
+   * {@code null} if this property is mapped directly with no conversion.
+   */
+  DtoConverterMeta converter() {
+    return converter;
+  }
+
+  /**
+   * Return a source expression chaining {@link #sourceGetterPath()} getters off the given root
+   * variable. A single getter is a plain call, e.g. {@code s.getName()}; a multi-hop chain (from
+   * {@code @DtoPath} or {@code @DtoRef}) null-guards each intermediate hop, e.g.
+   * {@code (s.getBillingAddress() == null ? null : s.getBillingAddress().getLine1())}.
+   */
+  String sourceValueExpression(String rootVariable) {
+    if (sourceGetterPath.size() == 1) {
+      return rootVariable + "." + sourceGetterPath.get(0) + "()";
+    }
+    StringBuilder sb = new StringBuilder();
+    appendGuardedChain(sb, rootVariable, 0);
+    return sb.toString();
+  }
+
+  private void appendGuardedChain(StringBuilder sb, String prefix, int index) {
+    if (index == sourceGetterPath.size() - 1) {
+      sb.append(prefix).append('.').append(sourceGetterPath.get(index)).append("()");
+      return;
+    }
+    String nextPrefix = prefix + "." + sourceGetterPath.get(index) + "()";
+    sb.append('(').append(nextPrefix).append(" == null ? null : ");
+    appendGuardedChain(sb, nextPrefix, index + 1);
+    sb.append(')');
+  }
+}

querybean-generator/src/main/java/io/ebean/querybean/generator/ProcessingContext.java

@@ -105,6 +105,14 @@ class ProcessingContext implements Constants {
     this.readModuleInfo = new ReadModuleInfo(this);
   }
 
+  Elements elementUtils() {
+    return elementUtils;
+  }
+
+  Types typeUtils() {
+    return typeUtils;
+  }
+
   TypeElement entityAnnotation() {
     return elementUtils.getTypeElement(ENTITY);
   }
@@ -693,6 +701,17 @@ class ProcessingContext implements Constants {
     return prefixEntities;
   }
 
+  /**
+   * True if any entity, embeddable or other (converter/component) class has been registered in
+   * this compilation - i.e. there is actually something for an {@code EbeanEntityRegister} to
+   * report. Guards against writing an empty, meaningless registry (with no factory package to
+   * derive a sensible location from) for compilation units - such as a test-source-only module
+   * that only declares {@code @DtoMapping} - that never contain any {@code @Entity} classes.
+   */
+  boolean hasAnyEntitiesOrOther() {
+    return !prefixEntities.isEmpty() || !otherClasses.isEmpty();
+  }
+
   Set<String> getDbEntities() {
     return dbEntities;
   }

querybean-generator/src/main/java/io/ebean/querybean/generator/Processor.java

@@ -17,8 +17,8 @@ import java.util.Set;
 public class Processor extends AbstractProcessor implements Constants {
 
   private ProcessingContext processingContext;
-  private SimpleModuleInfoWriter moduleWriter;
-  private boolean initModuleWriter;
+  private DtoMappingReader dtoMappingReader;
+  private boolean wroteDtoMappers;
 
   private boolean wroteLookup;
 
@@ -26,6 +26,7 @@ public class Processor extends AbstractProcessor implements Constants {
   public synchronized void init(ProcessingEnvironment processingEnv) {
     super.init(processingEnv);
     this.processingContext = new ProcessingContext(processingEnv);
+    this.dtoMappingReader = new DtoMappingReader(processingContext);
   }
 
   @Override
@@ -38,6 +39,9 @@ public class Processor extends AbstractProcessor implements Constants {
     annotations.add(MODULEINFO);
     annotations.add(TYPEQUERYBEAN);
     annotations.add(GENERATED);
+    annotations.add(DTO_MAPPING);
+    annotations.add(DTO_MAPPING_LIST);
+    annotations.add(DTO_MIXIN);
     return annotations;
   }
 
@@ -52,7 +56,10 @@ public class Processor extends AbstractProcessor implements Constants {
     int count = processEntities(roundEnv);
     processOthers(roundEnv);
     final int loaded = processingContext.complete();
-    initModuleInfoBean();
+    dtoMappingReader.collect(roundEnv);
+    if (!roundEnv.processingOver()) {
+      writeDtoMappers();
+    }
     if (roundEnv.processingOver()) {
       writeModuleInfoBean();
     }
@@ -101,29 +108,56 @@ public class Processor extends AbstractProcessor implements Constants {
     }
   }
 
-  private void initModuleInfoBean() {
+  /**
+   * Write the {@code EbeanEntityRegister} at the end of processing - deferred until there is
+   * something to actually register (rather than eagerly reserving/creating the source file up
+   * front), since a compilation unit with no {@code @Entity}/{@code @Embeddable}/{@code @Converter}
+   * /other classes at all - e.g. a test-source-only module that only declares
+   * {@code @DtoMapping} - has nothing meaningful to write and no factory package to derive a
+   * sensible location from.
+   */
+  private void writeModuleInfoBean() {
+    if (!processingContext.hasAnyEntitiesOrOther()) {
+      processingContext.logNote("EbeanEntityRegister skipped - no entities or other classes found");
+      return;
+    }
     try {
-      if (!initModuleWriter) {
-        moduleWriter = new SimpleModuleInfoWriter(processingContext);
-      }
+      SimpleModuleInfoWriter moduleWriter = new SimpleModuleInfoWriter(processingContext);
+      moduleWriter.write();
     } catch (FilerException e) {
       processingContext.logWarn(null, "FilerException trying to write EntityClassRegister error: " + e);
     } catch (Throwable e) {
-      processingContext.logError(null, "Failed to initialise EntityClassRegister error:" + e + " stack:" + Arrays.toString(e.getStackTrace()));
-    } finally {
-      initModuleWriter = true;
+      processingContext.logError(null, "Failed to write EntityClassRegister error:" + e + " stack:" + Arrays.toString(e.getStackTrace()));
     }
   }
 
-  private void writeModuleInfoBean() {
+  /**
+   * Generate the dto mappers as soon as all {@code @DtoMapping} pairs collected so far are
+   * available - i.e. as early as possible, not deferred to {@code roundEnv.processingOver()}.
+   * Generated types (unlike the {@code EbeanEntityRegister}/module-info registrations) are
+   * directly referenced by hand-written source code, so they must be written in a round prior
+   * to the final one or javac will not compile them at all (only a warning, no error, is
+   * produced for files created in the very last round - see "will not be subject to annotation
+   * processing").
+   */
+  private void writeDtoMappers() {
+    if (wroteDtoMappers) {
+      return;
+    }
     try {
-      if (moduleWriter == null) {
-        processingContext.logNote(null, "EntityClassRegister skipped");
-      } else {
-        moduleWriter.write();
+      var metas = dtoMappingReader.resolveAndValidate();
+      if (metas.isEmpty()) {
+        return;
       }
+      wroteDtoMappers = true;
+      for (DtoBeanMeta meta : metas) {
+        new DtoMapperWriter(processingContext, meta).write();
+      }
+      new DtoMapperRegisterWriter(processingContext, metas).write();
+      processingContext.logNote("Ebean APT generated %s dto mappers", metas.size());
     } catch (Throwable e) {
-      processingContext.logError(null, "Failed to write EntityClassRegister error:" + e + " stack:" + Arrays.toString(e.getStackTrace()));
+      wroteDtoMappers = true;
+      processingContext.logError(null, "Failed to generate dto mappers error:" + e + " stack:" + Arrays.toString(e.getStackTrace()));
     }
   }
 

querybean-generator/src/main/java/io/ebean/querybean/generator/Split.java

@@ -1,7 +1,9 @@
 package io.ebean.querybean.generator;
 
 import java.util.AbstractMap.SimpleEntry;
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.StringTokenizer;
@@ -54,4 +56,22 @@ class Split {
     return new SimpleEntry<>(simpleSignature.toString(), assocImports);
   }
 
+  /**
+   * Returns the first pair of distinct full names in {@code fullNames} that share the same
+   * simple (unqualified) class name, or {@code null} if there's no such collision - used to fail
+   * fast, with a clear diagnostic, on an ambiguous set of imports (two different types sharing a
+   * simple name) rather than silently generating source with a duplicate-import/undefined-symbol
+   * compile error that's much harder to trace back to its cause.
+   */
+  static String[] findSimpleNameCollision(Set<String> fullNames) {
+    Map<String, String> seenBySimpleName = new HashMap<>();
+    for (String fullName : fullNames) {
+      String existing = seenBySimpleName.putIfAbsent(shortName(fullName), fullName);
+      if (existing != null && !existing.equals(fullName)) {
+        return new String[] {existing, fullName};
+      }
+    }
+    return null;
+  }
+
 }

querybean-generator/src/main/java/io/ebean/querybean/generator/package-info.java

@@ -0,0 +1,11 @@
+/**
+ * Annotation processor generating type-safe Ebean Query beans and DTO graph mappers.
+ */
+@GeneratePrism(io.ebean.annotation.DtoPath.class)
+@GeneratePrism(io.ebean.annotation.DtoRef.class)
+@GeneratePrism(io.ebean.annotation.DtoMapping.class)
+@GeneratePrism(io.ebean.annotation.DtoConvert.class)
+@GeneratePrism(io.ebean.annotation.DtoMixin.class)
+package io.ebean.querybean.generator;
+
+import io.avaje.prism.GeneratePrism;

querybean-generator/src/main/java/module-info.java

@@ -4,4 +4,6 @@ module io.ebean.querybean.generator {
 
   requires java.compiler;
   requires java.sql;
+  requires static io.avaje.prism;
+  requires static io.ebean.annotation;
 }

querybean-generator/src/test/java/io/ebean/querybean/generator/DtoMapperFetchPathCollisionTest.java

@@ -0,0 +1,144 @@
+package io.ebean.querybean.generator;
+
+import org.junit.jupiter.api.Test;
+
+import javax.tools.Diagnostic;
+import javax.tools.DiagnosticCollector;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.ToolProvider;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.io.Writer;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Locale;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Regression test for the fetch-path collision fail-fast added to {@code DtoMapperWriter} - a
+ * {@code @DtoPath} property whose fetch path is identical to a {@code NESTED_ONE}/{@code NESTED_MANY}
+ * property's own fetch path (e.g. both resolve to path {@code "bar"}) must be a clear compile-time
+ * error, not silently generated code where one {@code .fetch("bar", ...)} call discards the other
+ * (see {@code OrmQueryDetail.fetch()}, which replaces rather than merges same-key entries).
+ * <p>
+ * Compiles a minimal in-memory source set directly through {@code javax.tools.JavaCompiler} with
+ * this module's {@link Processor} registered explicitly - no external compile-testing dependency
+ * required.
+ */
+class DtoMapperFetchPathCollisionTest {
+
+  @Test
+  void dtoPathCollidingWithNestedFetchPath_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-collision-src");
+    Path outDir = Files.createTempDirectory("dto-collision-out");
+    writeSource(sourceDir, "org.tests.collision.Bar",
+      "package org.tests.collision;\n"
+        + "\n"
+        + "public class Bar {\n"
+        + "  private Long id;\n"
+        + "  private String name;\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.collision.Foo",
+      "package org.tests.collision;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private Bar bar;\n"
+        + "\n"
+        + "  public Bar getBar() { return bar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.collision.BarDto",
+      "package org.tests.collision;\n"
+        + "\n"
+        + "public class BarDto {\n"
+        + "  private final Long id;\n"
+        + "  private final String name;\n"
+        + "\n"
+        + "  public BarDto(Long id, String name) {\n"
+        + "    this.id = id;\n"
+        + "    this.name = name;\n"
+        + "  }\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.collision.FooDto",
+      "package org.tests.collision;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoPath;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  private final BarDto bar;\n"
+        + "\n"
+        + "  @DtoPath(\"bar.name\")\n"
+        + "  private final String barName;\n"
+        + "\n"
+        + "  public FooDto(BarDto bar, String barName) {\n"
+        + "    this.bar = bar;\n"
+        + "    this.barName = barName;\n"
+        + "  }\n"
+        + "\n"
+        + "  public BarDto getBar() { return bar; }\n"
+        + "  public String getBarName() { return barName; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.collision.package-info",
+      "@DtoMapping(source = Bar.class, target = BarDto.class)\n"
+        + "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.collision;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoMapping;\n");
+
+    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
+    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+    try (StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, Locale.getDefault(), null)) {
+      List<Path> sourceFiles;
+      try (var walk = Files.walk(sourceDir)) {
+        sourceFiles = walk.filter(p -> p.toString().endsWith(".java")).collect(Collectors.toList());
+      }
+      Iterable<? extends JavaFileObject> compilationUnits =
+        fileManager.getJavaFileObjectsFromPaths(sourceFiles);
+
+      List<String> options = List.of(
+        "-d", outDir.toString(),
+        "-classpath", System.getProperty("java.class.path"),
+        "-processor", Processor.class.getName());
+
+      JavaCompiler.CompilationTask task = compiler.getTask(
+        null, fileManager, diagnostics, options, null, compilationUnits);
+      boolean success = task.call();
+
+      assertFalse(success, "compilation should fail due to the fetch path collision");
+      List<Diagnostic<? extends JavaFileObject>> errors = diagnostics.getDiagnostics().stream()
+        .filter(d -> d.getKind() == Diagnostic.Kind.ERROR)
+        .collect(Collectors.toList());
+      assertFalse(errors.isEmpty(), "expected at least one compile ERROR diagnostic");
+      boolean matched = errors.stream()
+        .map(d -> d.getMessage(Locale.getDefault()))
+        .anyMatch(msg -> msg.contains("resolves to fetch path 'bar'")
+          && msg.contains("collides with the nested mapping"));
+      assertTrue(matched, "expected the fetch-path-collision error message, got: " + errors);
+    }
+  }
+
+  private void writeSource(Path sourceDir, String fqn, String content) {
+    try {
+      Path pkgDir = sourceDir.resolve(fqn.substring(0, fqn.lastIndexOf('.')).replace('.', '/'));
+      Files.createDirectories(pkgDir);
+      String simpleName = fqn.substring(fqn.lastIndexOf('.') + 1);
+      Path file = pkgDir.resolve(simpleName + ".java");
+      try (Writer writer = Files.newBufferedWriter(file)) {
+        writer.write(content);
+      }
+    } catch (IOException e) {
+      throw new UncheckedIOException(e);
+    }
+  }
+}

querybean-generator/src/test/java/io/ebean/querybean/generator/DtoMapperRecordSourceTest.java

@@ -0,0 +1,252 @@
+package io.ebean.querybean.generator;
+
+import org.junit.jupiter.api.Test;
+
+import javax.tools.Diagnostic;
+import javax.tools.DiagnosticCollector;
+import javax.tools.JavaCompiler;
+import javax.tools.JavaFileObject;
+import javax.tools.StandardJavaFileManager;
+import javax.tools.ToolProvider;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.io.Writer;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Locale;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Regression test proving DTO mapping resolves the correct source accessor for two non-JavaBean
+ * accessor shapes - both a genuine Java {@code record} source (see {@code
+ * org.example.records.CourseRecordEntity} in {@code test-java16}) and, separately, an ordinary
+ * (non-record) class that simply exposes bare/fluent-style accessors (e.g. {@code active()},
+ * {@code name()}) with no {@code get}/{@code is} prefix at all - Ebean supports record entity
+ * beans, but a bare-name accessor isn't exclusive to an actual {@code record} type. Both the
+ * accessor call generated for reading the source value, and the Ebean bean-property name used in
+ * the generated {@code FetchGroup.select(...)}/{@code .fetch(...)} calls, must match whichever
+ * shape the source type actually exposes, rather than blindly guessing a JavaBean {@code get}/
+ * {@code is} prefix.
+ */
+class DtoMapperRecordSourceTest {
+
+  @Test
+  void recordSource_expectBareAccessorsAndPropertyNames() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-record-src");
+    Path outDir = Files.createTempDirectory("dto-record-out");
+    Path genSourceDir = Files.createTempDirectory("dto-record-gensrc");
+
+    writeSource(sourceDir, "org.tests.recordsrc.Region",
+      "package org.tests.recordsrc;\n"
+        + "\n"
+        + "public record Region(long id, String code) {\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.recordsrc.ItemRecord",
+      "package org.tests.recordsrc;\n"
+        + "\n"
+        + "public record ItemRecord(long id, String name, boolean active, Region region) {\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.recordsrc.ItemDto",
+      "package org.tests.recordsrc;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoRef;\n"
+        + "\n"
+        + "public class ItemDto {\n"
+        + "  private final long id;\n"
+        + "  private final String name;\n"
+        + "  private final boolean active;\n"
+        + "  @DtoRef\n"
+        + "  private final Long regionId;\n"
+        + "\n"
+        + "  public ItemDto(long id, String name, boolean active, Long regionId) {\n"
+        + "    this.id = id;\n"
+        + "    this.name = name;\n"
+        + "    this.active = active;\n"
+        + "    this.regionId = regionId;\n"
+        + "  }\n"
+        + "\n"
+        + "  public long getId() { return id; }\n"
+        + "  public String getName() { return name; }\n"
+        + "  public boolean isActive() { return active; }\n"
+        + "  public Long getRegionId() { return regionId; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.recordsrc.package-info",
+      "@DtoMapping(source = ItemRecord.class, target = ItemDto.class)\n"
+        + "package org.tests.recordsrc;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoMapping;\n");
+    writeTypequeryGeneratedStub(sourceDir);
+
+    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
+    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+    try (StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, Locale.getDefault(), null)) {
+      List<Path> sourceFiles;
+      try (var walk = Files.walk(sourceDir)) {
+        sourceFiles = walk.filter(p -> p.toString().endsWith(".java")).collect(Collectors.toList());
+      }
+      Iterable<? extends JavaFileObject> compilationUnits =
+        fileManager.getJavaFileObjectsFromPaths(sourceFiles);
+
+      List<String> options = List.of(
+        "-d", outDir.toString(),
+        "-s", genSourceDir.toString(),
+        "-processor", Processor.class.getName());
+
+      JavaCompiler.CompilationTask task = compiler.getTask(
+        null, fileManager, diagnostics, options, null, compilationUnits);
+      boolean success = task.call();
+
+      List<Diagnostic<? extends JavaFileObject>> errors = diagnostics.getDiagnostics().stream()
+        .filter(d -> d.getKind() == Diagnostic.Kind.ERROR)
+        .collect(Collectors.toList());
+      assertTrue(success, "compilation should succeed for a record source type, got errors: " + errors);
+
+      Path mapperFile;
+      try (var walk = Files.walk(genSourceDir)) {
+        mapperFile =         walk.filter(p -> p.getFileName().toString().equals("ItemDtoMapper.java"))
+          .findFirst()
+          .orElseThrow(() -> new AssertionError("generated mapper source not found under " + genSourceDir));
+      }
+      String generated = Files.readString(mapperFile);
+
+      assertTrue(generated.contains("source.name()"), "expected bare record accessor source.name(), got:\n" + generated);
+      assertTrue(generated.contains("source.active()"), "expected bare record accessor source.active(), got:\n" + generated);
+      assertFalse(generated.contains("getName()"), "should not guess a JavaBean getter for a record source, got:\n" + generated);
+      assertFalse(generated.contains("isActive()"), "should not guess an isXxx() getter for a record source, got:\n" + generated);
+      assertFalse(generated.contains("getActive()"), "should not guess a getXxx() getter for a record source, got:\n" + generated);
+
+      assertTrue(generated.contains("select(\"id,name,active,region\")"),
+        "expected FetchGroup.select(...) to use bare Ebean property names, got:\n" + generated);
+
+      assertTrue(generated.contains("source.region() == null ? null : source.region().id()"),
+        "expected @DtoRef id shortcut to use the associated record's bare id() accessor, got:\n" + generated);
+    }
+  }
+
+  @Test
+  void plainClassWithBareAccessors_expectBareAccessorsResolved() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-bare-src");
+    Path outDir = Files.createTempDirectory("dto-bare-out");
+    Path genSourceDir = Files.createTempDirectory("dto-bare-gensrc");
+
+    writeSource(sourceDir, "org.tests.baresrc.WidgetSource",
+      "package org.tests.baresrc;\n"
+        + "\n"
+        + "public class WidgetSource {\n"
+        + "  private final long id;\n"
+        + "  private final String name;\n"
+        + "  private final boolean active;\n"
+        + "\n"
+        + "  public WidgetSource(long id, String name, boolean active) {\n"
+        + "    this.id = id;\n"
+        + "    this.name = name;\n"
+        + "    this.active = active;\n"
+        + "  }\n"
+        + "\n"
+        + "  public long id() { return id; }\n"
+        + "  public String name() { return name; }\n"
+        + "  public boolean active() { return active; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.baresrc.WidgetDto",
+      "package org.tests.baresrc;\n"
+        + "\n"
+        + "public class WidgetDto {\n"
+        + "  private final long id;\n"
+        + "  private final String name;\n"
+        + "  private final boolean active;\n"
+        + "\n"
+        + "  public WidgetDto(long id, String name, boolean active) {\n"
+        + "    this.id = id;\n"
+        + "    this.name = name;\n"
+        + "    this.active = active;\n"
+        + "  }\n"
+        + "\n"
+        + "  public long getId() { return id; }\n"
+        + "  public String getName() { return name; }\n"
+        + "  public boolean isActive() { return active; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.baresrc.package-info",
+      "@DtoMapping(source = WidgetSource.class, target = WidgetDto.class)\n"
+        + "package org.tests.baresrc;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoMapping;\n");
+    writeTypequeryGeneratedStub(sourceDir);
+
+    DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
+    JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
+    try (StandardJavaFileManager fileManager = compiler.getStandardFileManager(diagnostics, Locale.getDefault(), null)) {
+      List<Path> sourceFiles;
+      try (var walk = Files.walk(sourceDir)) {
+        sourceFiles = walk.filter(p -> p.toString().endsWith(".java")).collect(Collectors.toList());
+      }
+      Iterable<? extends JavaFileObject> compilationUnits =
+        fileManager.getJavaFileObjectsFromPaths(sourceFiles);
+
+      List<String> options = List.of(
+        "-d", outDir.toString(),
+        "-s", genSourceDir.toString(),
+        "-processor", Processor.class.getName());
+
+      JavaCompiler.CompilationTask task = compiler.getTask(
+        null, fileManager, diagnostics, options, null, compilationUnits);
+      boolean success = task.call();
+
+      List<Diagnostic<? extends JavaFileObject>> errors = diagnostics.getDiagnostics().stream()
+        .filter(d -> d.getKind() == Diagnostic.Kind.ERROR)
+        .collect(Collectors.toList());
+      assertTrue(success, "compilation should succeed for a plain class with bare accessors, got errors: " + errors);
+
+      Path mapperFile;
+      try (var walk = Files.walk(genSourceDir)) {
+        mapperFile = walk.filter(p -> p.getFileName().toString().equals("WidgetDtoMapper.java"))
+          .findFirst()
+          .orElseThrow(() -> new AssertionError("generated mapper source not found under " + genSourceDir));
+      }
+      String generated = Files.readString(mapperFile);
+
+      assertTrue(generated.contains("source.id()"), "expected bare accessor source.id(), got:\n" + generated);
+      assertTrue(generated.contains("source.name()"), "expected bare accessor source.name(), got:\n" + generated);
+      assertTrue(generated.contains("source.active()"), "expected bare accessor source.active(), got:\n" + generated);
+      assertFalse(generated.contains("getName()"), "should not guess a JavaBean getter, got:\n" + generated);
+      assertFalse(generated.contains("isActive()"), "should not guess an isXxx() getter, got:\n" + generated);
+      assertFalse(generated.contains("getActive()"), "should not guess a getXxx() getter, got:\n" + generated);
+
+      assertTrue(generated.contains("select(\"id,name,active\")"),
+        "expected FetchGroup.select(...) to use bare Ebean property names, got:\n" + generated);
+    }
+  }
+
+  /**
+   * The generated mapper source references {@code io.ebean.typequery.Generated} ({@code
+   * ebean-querybean}) - that can't be a real dependency here (it would create a circular reactor
+   * module dependency since {@code ebean-querybean} depends on {@code querybean-generator}).
+   * Write a self-contained stub of just that one annotation alongside the test sources so the
+   * generated mapper source fully compiles without needing the real module.
+   */
+  private void writeTypequeryGeneratedStub(Path sourceDir) {
+    writeSource(sourceDir, "io.ebean.typequery.Generated",
+      "package io.ebean.typequery;\n"
+        + "\n"
+        + "public @interface Generated {\n"
+        + "  String value();\n"
+        + "}\n");
+  }
+
+  private void writeSource(Path sourceDir, String fqn, String content) {
+    try {
+      Path pkgDir = sourceDir.resolve(fqn.substring(0, fqn.lastIndexOf('.')).replace('.', '/'));
+      Files.createDirectories(pkgDir);
+      String simpleName = fqn.substring(fqn.lastIndexOf('.') + 1);
+      Path file = pkgDir.resolve(simpleName + ".java");
+      try (Writer writer = Files.newBufferedWriter(file)) {
+        writer.write(content);
+      }
+    } catch (IOException e) {
+      throw new UncheckedIOException(e);
+    }
+  }
+}

tests/test-dto-mapping/pom.xml

@@ -0,0 +1,103 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <artifactId>tests</artifactId>
+    <groupId>io.ebean</groupId>
+    <version>18.2.0</version>
+  </parent>
+
+  <artifactId>test-dto-mapping</artifactId>
+
+  <name>test dto mapping</name>
+  <description>
+    Standalone validation module for issue #2540 nested DTO mapping codegen
+    (dto-codegen-mapper) - wires querybean-generator as an annotation processor (via
+    provided-scope dependency, mirroring test-java16) so its generated XxxMapper classes and
+    EbeanDtoMapperRegister can be exercised end-to-end, which the main ebean-test module cannot
+    do since it does not wire querybean-generator at all.
+  </description>
+
+  <dependencies>
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>ebean-h2</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>ch.qos.logback</groupId>
+      <artifactId>logback-classic</artifactId>
+      <version>1.3.12</version>
+    </dependency>
+
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>ebean-test</artifactId>
+      <version>${project.version}</version>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>io.ebean</groupId>
+      <artifactId>querybean-generator</artifactId>
+      <version>${project.version}</version>
+      <scope>provided</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.assertj</groupId>
+      <artifactId>assertj-core</artifactId>
+      <version>3.27.7</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <configuration>
+          <annotationProcessorPaths>
+            <path>
+              <groupId>io.ebean</groupId>
+              <artifactId>querybean-generator</artifactId>
+              <version>${project.version}</version>
+            </path>
+          </annotationProcessorPaths>
+        </configuration>
+      </plugin>
+
+      <plugin>
+        <groupId>io.ebean</groupId>
+        <artifactId>ebean-maven-plugin</artifactId>
+        <version>${ebean-maven-plugin.version}</version>
+        <executions>
+          <execution>
+            <id>main</id>
+            <phase>process-classes</phase>
+            <configuration>
+              <transformArgs>debug=0</transformArgs>
+            </configuration>
+            <goals>
+              <goal>enhance</goal>
+            </goals>
+          </execution>
+          <execution>
+            <id>test</id>
+            <phase>process-test-classes</phase>
+            <configuration>
+              <transformArgs>debug=0</transformArgs>
+            </configuration>
+            <goals>
+              <goal>testEnhance</goal>
+            </goals>
+          </execution>
+        </executions>
+      </plugin>
+    </plugins>
+  </build>
+
+</project>

tests/test-dto-mapping/src/main/java/org/tests/dtomapping/model/Address.java

@@ -0,0 +1,40 @@
+package org.tests.dtomapping.model;
+
+import io.ebean.Model;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+@Entity
+public class Address extends Model {
+
+  @Id
+  private Long id;
+
+  private String line1;
+  private String city;
+
+  public Address(String line1, String city) {
+    this.line1 = line1;
+    this.city = city;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getLine1() {
+    return line1;
+  }
+
+  public void setLine1(String line1) {
+    this.line1 = line1;
+  }
+
+  public String getCity() {
+    return city;
+  }
+
+  public void setCity(String city) {
+    this.city = city;
+  }
+}

tests/test-dto-mapping/src/main/java/org/tests/dtomapping/model/Contact.java

@@ -0,0 +1,107 @@
+package org.tests.dtomapping.model;
+
+import io.ebean.Model;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
+
+@Entity
+public class Contact extends Model {
+
+  @Id
+  private Long id;
+
+  private String firstName;
+  private String lastName;
+
+  /**
+   * Primitive {@code boolean} field, mapped directly (no {@code @DtoPath}/{@code @DtoConvert}) -
+   * exercises the generator resolving {@code isActive()} rather than guessing {@code getActive()}
+   * for the source accessor (standard JavaBean convention for a primitive boolean).
+   */
+  private boolean active = true;
+
+  @ManyToOne
+  private Customer customer;
+
+  /** Per-contact engagement score - purely so {@link ContactStats} has something to {@code @Sum}. */
+  private Integer engagementScore;
+
+  /**
+   * Stored as a raw {@code Short} (0/1) - a stand-in for the kind of legacy scalar encoding
+   * {@code @DtoConvert}'s static dispatch is meant for (e.g. {@code short} to {@code boolean}).
+   */
+  private Short status;
+
+  /**
+   * Stand-in for a value needing a real dependency to convert (e.g. a cipher) - a stand-in for
+   * {@code @DtoConvert}'s instance dispatch, resolved via {@code DtoConverterManager}.
+   */
+  private String secretCode;
+
+  public Contact(String firstName, String lastName, Customer customer) {
+    this.firstName = firstName;
+    this.lastName = lastName;
+    this.customer = customer;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public void setFirstName(String firstName) {
+    this.firstName = firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+
+  public void setLastName(String lastName) {
+    this.lastName = lastName;
+  }
+
+  public boolean isActive() {
+    return active;
+  }
+
+  public void setActive(boolean active) {
+    this.active = active;
+  }
+
+  public Customer getCustomer() {
+    return customer;
+  }
+
+  public void setCustomer(Customer customer) {
+    this.customer = customer;
+  }
+
+  public Integer getEngagementScore() {
+    return engagementScore;
+  }
+
+  public void setEngagementScore(Integer engagementScore) {
+    this.engagementScore = engagementScore;
+  }
+
+  public Short getStatus() {
+    return status;
+  }
+
+  public void setStatus(Short status) {
+    this.status = status;
+  }
+
+  public String getSecretCode() {
+    return secretCode;
+  }
+
+  public void setSecretCode(String secretCode) {
+    this.secretCode = secretCode;
+  }
+}

tests/test-dto-mapping/src/main/java/org/tests/dtomapping/model/ContactStats.java

@@ -0,0 +1,54 @@
+package org.tests.dtomapping.model;
+
+import io.ebean.Model;
+import io.ebean.annotation.Aggregation;
+import io.ebean.annotation.Sum;
+import io.ebean.annotation.View;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
+
+/**
+ * Per-customer contact aggregates, read through the same {@code contact} table as {@link Contact}
+ * (rather than a real database view or a new table - {@code @View(name = "contact")} just points
+ * this entity's base table at the existing one, so no new DDL is generated).
+ * <p>
+ * This is the worked example for Blaze-Persistence-style aggregate/group-by mappings (see
+ * docs/dto-mapping-design.md, "Aggregate/group-by computed properties"): {@code contactCount} and
+ * {@code engagementScore} are group-by aggregate formulas ({@code @Aggregation}/{@code @Sum}),
+ * grouped implicitly by whichever non-aggregate properties end up selected - here {@code customer}.
+ * The Blaze-Persistence parallel is an {@code @EntityView} with {@code @Mapping("SIZE(contacts)")}
+ * / {@code @Mapping("SUM(contacts.engagementScore)")} correlated mappings.
+ * <p>
+ * {@code id} is declared (required so {@code @Aggregation("count(id)")} has a property to count)
+ * but deliberately never selected/mapped - selecting it would defeat the aggregation by grouping
+ * one row per contact instead of one row per customer.
+ */
+@Entity
+@View(name = "contact")
+public class ContactStats extends Model {
+
+  @Id
+  private Long id;
+
+  @ManyToOne
+  private Customer customer;
+
+  @Aggregation("count(id)")
+  private Long contactCount;
+
+  @Sum
+  private Integer engagementScore;
+
+  public Customer getCustomer() {
+    return customer;
+  }
+
+  public Long getContactCount() {
+    return contactCount;
+  }
+
+  public Integer getEngagementScore() {
+    return engagementScore;
+  }
+}

tests/test-dto-mapping/src/main/java/org/tests/dtomapping/model/ContactSummary.java

@@ -0,0 +1,53 @@
+package org.tests.dtomapping.model;
+
+import io.ebean.annotation.Formula2;
+import io.ebean.annotation.View;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+
+/**
+ * Worked example: a read-only "view" entity mapped onto the *same* underlying table as
+ * {@link Contact} (via {@code @View(name = "contact")}) rather than a real database view -
+ * this deliberately generates no DDL of its own, it just reads {@link Contact}'s table
+ * through a second, purpose-built entity shape.
+ * <p>
+ * This is the pattern proposed in docs/dto-mapping-design.md's "Ad-hoc computed/formula
+ * properties" section as the preferred way to get a Blaze-Persistence-style computed DTO
+ * property: model the computed value as a plain {@code @Formula2} on a dedicated read
+ * entity, then map that entity to a DTO with the existing (unmodified) {@code @DtoMapping}
+ * machinery - no new ad-hoc-SQL-on-DTO annotation required.
+ */
+@Entity
+@View(name = "contact")
+public class ContactSummary {
+
+  @Id
+  private Long id;
+
+  private String firstName;
+  private String lastName;
+
+  /**
+   * Computed purely from {@link #firstName} and {@link #lastName} - no join required, but
+   * demonstrates the same {@code @Formula2} mechanism used for join-requiring formulas
+   * elsewhere (see {@code AggStockProduct}/{@code ParentPerson} in ebean-test).
+   */
+  @Formula2("concat(firstName, ' ', lastName)")
+  private String fullName;
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+
+  public String getFullName() {
+    return fullName;
+  }
+}

tests/test-dto-mapping/src/main/java/org/tests/dtomapping/model/Customer.java

@@ -0,0 +1,52 @@
+package org.tests.dtomapping.model;
+
+import io.ebean.Model;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.OneToMany;
+import java.util.ArrayList;
+import java.util.List;
+
+@Entity
+public class Customer extends Model {
+
+  @Id
+  private Long id;
+
+  private String name;
+
+  @ManyToOne
+  private Address billingAddress;
+
+  @OneToMany(mappedBy = "customer")
+  private List<Contact> contacts = new ArrayList<>();
+
+  public Customer(String name) {
+    this.name = name;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public void setName(String name) {
+    this.name = name;
+  }
+
+  public Address getBillingAddress() {
+    return billingAddress;
+  }
+
+  public void setBillingAddress(Address billingAddress) {
+    this.billingAddress = billingAddress;
+  }
+
+  public List<Contact> getContacts() {
+    return contacts;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/AddressDto.java

@@ -0,0 +1,29 @@
+package org.tests.dtomapping;
+
+/**
+ * Plain DTO with no framework attachment - nested ToOne target for {@link CustomerDto}.
+ */
+public class AddressDto {
+
+  private final Long id;
+  private final String line1;
+  private final String city;
+
+  public AddressDto(Long id, String line1, String city) {
+    this.id = id;
+    this.line1 = line1;
+    this.city = city;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getLine1() {
+    return line1;
+  }
+
+  public String getCity() {
+    return city;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactBuilderDto.java

@@ -0,0 +1,103 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoRef;
+
+/**
+ * Builder-constructed DTO for requirement r18 - forced via {@code @DtoMapping(builder = ALWAYS)}
+ * on the {@code package-info.java} declaration. Follows the {@code avaje-recordbuilder}
+ * convention by hand (no dependency on that library needed just to test detection): a static
+ * no-arg {@code builder()} factory method, a fluent (returns-itself) same-named setter per
+ * property, and a no-arg {@code build()} method returning the target type.
+ */
+public class ContactBuilderDto {
+
+  private final Long id;
+  private final String firstName;
+  private final String lastName;
+  private final Short status;
+  private final String secretCode;
+
+  @DtoRef
+  private final Long customerId;
+
+  private ContactBuilderDto(Builder builder) {
+    this.id = builder.id;
+    this.firstName = builder.firstName;
+    this.lastName = builder.lastName;
+    this.status = builder.status;
+    this.secretCode = builder.secretCode;
+    this.customerId = builder.customerId;
+  }
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+
+  public Short getStatus() {
+    return status;
+  }
+
+  public String getSecretCode() {
+    return secretCode;
+  }
+
+  public Long getCustomerId() {
+    return customerId;
+  }
+
+  public static final class Builder {
+
+    private Long id;
+    private String firstName;
+    private String lastName;
+    private Short status;
+    private String secretCode;
+    private Long customerId;
+
+    public Builder id(Long id) {
+      this.id = id;
+      return this;
+    }
+
+    public Builder firstName(String firstName) {
+      this.firstName = firstName;
+      return this;
+    }
+
+    public Builder lastName(String lastName) {
+      this.lastName = lastName;
+      return this;
+    }
+
+    public Builder status(Short status) {
+      this.status = status;
+      return this;
+    }
+
+    public Builder secretCode(String secretCode) {
+      this.secretCode = secretCode;
+      return this;
+    }
+
+    public Builder customerId(Long customerId) {
+      this.customerId = customerId;
+      return this;
+    }
+
+    public ContactBuilderDto build() {
+      return new ContactBuilderDto(this);
+    }
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactConversionDbConfigProvider.java

@@ -0,0 +1,22 @@
+package org.tests.dtomapping;
+
+import io.ebean.DatabaseBuilder;
+import io.ebean.DtoConverterManager;
+import io.ebean.config.DatabaseConfigProvider;
+
+/**
+ * Registers the {@link SecretCipher} instance needed by {@link ContactConversionDto}'s
+ * {@code @DtoConvert} instance-dispatch conversion, via the standard
+ * {@code DatabaseConfigProvider} ServiceLoader hook (see
+ * {@code META-INF/services/io.ebean.config.DatabaseConfigProvider}) - which runs before the
+ * {@code Database} (and so the generated {@code EbeanDtoMapperRegister}) is built, satisfying
+ * {@code DtoConverterManager}'s "register before starting the Database" requirement regardless
+ * of which test happens to trigger the default {@code Database}'s startup first.
+ */
+public class ContactConversionDbConfigProvider implements DatabaseConfigProvider {
+
+  @Override
+  public void apply(DatabaseBuilder config) {
+    DtoConverterManager.put(SecretCipher.class, new ReverseSecretCipher());
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactConversionDto.java

@@ -0,0 +1,47 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoConvert;
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Standalone (not nested under {@link ContactDto}) DTO exercising {@code @DtoConvert} - both the
+ * static-dispatch (requirement r13, {@link #active}) and instance-dispatch (requirement r14,
+ * {@link #secretCode}) cases - see {@code docs/dto-mapping-requirements.md} "Section E: Custom
+ * property conversion".
+ */
+public class ContactConversionDto {
+
+  private final long id;
+  private final String firstName;
+
+  /** {@code Contact.status} (a raw {@code Short}) converted via the static {@link ContactConversions#toActive}. */
+  @DtoPath("status")
+  @DtoConvert(value = ContactConversions.class, method = "toActive")
+  private final boolean active;
+
+  @DtoConvert(value = SecretCipher.class, method = "decode")
+  private final String secretCode;
+
+  public ContactConversionDto(long id, String firstName, boolean active, String secretCode) {
+    this.id = id;
+    this.firstName = firstName;
+    this.active = active;
+    this.secretCode = secretCode;
+  }
+
+  public long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public boolean isActive() {
+    return active;
+  }
+
+  public String getSecretCode() {
+    return secretCode;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactConversions.java

@@ -0,0 +1,16 @@
+package org.tests.dtomapping;
+
+/**
+ * Static, dependency-free scalar conversions - the {@code @DtoConvert} static-dispatch case
+ * (requirement r13): no registration needed, the generated mapper calls
+ * {@code ContactConversions.toActive(...)} directly.
+ */
+public final class ContactConversions {
+
+  private ContactConversions() {
+  }
+
+  public static boolean toActive(Short status) {
+    return status != null && status != 0;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactDto.java

@@ -0,0 +1,66 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+import io.ebean.annotation.DtoRef;
+
+public class ContactDto {
+
+  private final long id;
+  private final String firstName;
+  private final String lastName;
+  /** Direct scalar mapping of a primitive {@code boolean} source field - see {@link org.tests.dtomapping.model.Contact#isActive()}. */
+  private final boolean active;
+  private final CustomerRefDto customer;
+
+  /** {@code @DtoRef} id-only shortcut - {@code s.getCustomer().getId()}, no nested mapper. */
+  @DtoRef
+  private final Long customerId;
+
+  /**
+   * {@code @DtoPath} multi-hop getter chain - {@code s.getCustomer().getBillingAddress().getCity()},
+   * null-guarded at each hop. Deliberately a 2-hop path through {@code customer} (rather than
+   * repeating the {@code billingAddress.line1} example already used elsewhere) so its fetch path
+   * ({@code customer.billingAddress}) doesn't collide with the plain {@code customer} nested-DTO
+   * fetch on this same class.
+   */
+  @DtoPath("customer.billingAddress.city")
+  private final String customerCity;
+
+  public ContactDto(long id, String firstName, String lastName, boolean active, CustomerRefDto customer, Long customerId, String customerCity) {
+    this.id = id;
+    this.firstName = firstName;
+    this.lastName = lastName;
+    this.active = active;
+    this.customer = customer;
+    this.customerId = customerId;
+    this.customerCity = customerCity;
+  }
+
+  public long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+
+  public boolean isActive() {
+    return active;
+  }
+
+  public CustomerRefDto getCustomer() {
+    return customer;
+  }
+
+  public Long getCustomerId() {
+    return customerId;
+  }
+
+  public String getCustomerCity() {
+    return customerCity;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactMixinDto.java

@@ -0,0 +1,45 @@
+package org.tests.dtomapping;
+
+/**
+ * Stand-in for a DTO that can't be annotated directly (e.g. generated from an OpenAPI spec,
+ * regenerated on every build) - carries no {@code @DtoPath}/{@code @DtoRef}/{@code @DtoConvert}
+ * annotations of its own at all. {@link ContactMixinDtoMixin} overlays them instead (requirement
+ * "Section E: Custom property conversion" / {@code @DtoMixin} in
+ * docs/dto-mapping-requirements.md).
+ */
+public class ContactMixinDto {
+
+  private final long id;
+  private final String firstName;
+  private final boolean active;
+  private final String secretCode;
+  private final CustomerRefDto owner;
+
+  public ContactMixinDto(long id, String firstName, boolean active, String secretCode, CustomerRefDto owner) {
+    this.id = id;
+    this.firstName = firstName;
+    this.active = active;
+    this.secretCode = secretCode;
+    this.owner = owner;
+  }
+
+  public long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public boolean isActive() {
+    return active;
+  }
+
+  public String getSecretCode() {
+    return secretCode;
+  }
+
+  public CustomerRefDto getOwner() {
+    return owner;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactMixinDtoMixin.java

@@ -0,0 +1,31 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoConvert;
+import io.ebean.annotation.DtoMixin;
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Overlays {@code @DtoPath}/{@code @DtoConvert} onto {@link ContactMixinDto}, which carries no
+ * annotations of its own - mirrors avaje-jsonb's {@code @Json.MixIn} mechanism. Method names
+ * match {@link ContactMixinDto}'s field names ({@code active}, {@code secretCode}, {@code owner});
+ * the querybean generator matches each mixin method to the corresponding target property by name
+ * and applies whichever annotations are present as if declared on the target field itself.
+ */
+@DtoMixin(ContactMixinDto.class)
+interface ContactMixinDtoMixin {
+
+  @DtoPath("status")
+  @DtoConvert(value = ContactConversions.class, method = "toActive")
+  boolean active();
+
+  @DtoConvert(value = SecretCipher.class, method = "decode")
+  String secretCode();
+
+  /**
+   * A single-hop {@code @DtoPath} rename onto a nested (registered {@code @DtoMapping}) type -
+   * {@code owner} is renamed from {@code Contact#getCustomer()}, resolving to
+   * {@code CustomerRefDto} via its own generated mapper rather than a raw scalar getter call.
+   */
+  @DtoPath("customer")
+  CustomerRefDto owner();
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactStatsDto.java

@@ -0,0 +1,38 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoRef;
+
+/**
+ * Flat DTO for {@link org.tests.dtomapping.model.ContactStats} - a group-by aggregation result
+ * (contact count + summed engagement score per customer), not a graph fetch.
+ * <p>
+ * {@code customerId} uses {@code @DtoRef} - the generated fetch spec adds {@code customer} to the
+ * root {@code select(...)}, which reads the FK column directly off the base table (no join) and
+ * is exactly the property this aggregation query is grouped by. This doubles as the grouping key.
+ */
+public class ContactStatsDto {
+
+  @DtoRef
+  private final Long customerId;
+
+  private final Long contactCount;
+  private final Integer engagementScore;
+
+  public ContactStatsDto(Long customerId, Long contactCount, Integer engagementScore) {
+    this.customerId = customerId;
+    this.contactCount = contactCount;
+    this.engagementScore = engagementScore;
+  }
+
+  public Long getCustomerId() {
+    return customerId;
+  }
+
+  public Long getContactCount() {
+    return contactCount;
+  }
+
+  public Integer getEngagementScore() {
+    return engagementScore;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ContactSummaryDto.java

@@ -0,0 +1,25 @@
+package org.tests.dtomapping;
+
+/**
+ * Plain DTO with no framework attachment - mapping target for {@code ContactSummary}, the
+ * worked example of a {@code @Formula2}-backed computed property flowing into a DTO via a
+ * dedicated {@code @View}-mapped read entity rather than a bespoke ad-hoc-SQL-on-DTO feature.
+ */
+public class ContactSummaryDto {
+
+  private final Long id;
+  private final String fullName;
+
+  public ContactSummaryDto(Long id, String fullName) {
+    this.id = id;
+    this.fullName = fullName;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFullName() {
+    return fullName;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/CustomerDto.java

@@ -0,0 +1,39 @@
+package org.tests.dtomapping;
+
+import java.util.List;
+
+/**
+ * Plain DTO with no framework attachment - target of the nested DTO graph mapping spike for
+ * issue #2540. Nests {@link AddressDto} for the {@code billingAddress} ToOne relationship and
+ * {@link ContactDto} for the {@code contacts} ToMany relationship.
+ */
+public class CustomerDto {
+
+  private final Long id;
+  private final String name;
+  private final AddressDto billingAddress;
+  private final List<ContactDto> contacts;
+
+  public CustomerDto(Long id, String name, AddressDto billingAddress, List<ContactDto> contacts) {
+    this.id = id;
+    this.name = name;
+    this.billingAddress = billingAddress;
+    this.contacts = contacts;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public AddressDto getBillingAddress() {
+    return billingAddress;
+  }
+
+  public List<ContactDto> getContacts() {
+    return contacts;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/CustomerRefDto.java

@@ -0,0 +1,28 @@
+package org.tests.dtomapping;
+
+/**
+ * Shallow reference DTO for {@code Customer} - deliberately does <b>not</b> include a
+ * {@code contacts} field (or any other back-reference), so that {@link ContactDto#getCustomer()}
+ * can point back to its owning customer without re-introducing the {@code Customer -> Contact ->
+ * Customer} cycle. This is the hand-written analogue of the {@code @DtoRef} escape hatch
+ * described in docs/dto-mapping-design.md, just modelled as a distinct shallow DTO type here
+ * rather than an id-only field.
+ */
+public class CustomerRefDto {
+
+  private final Long id;
+  private final String name;
+
+  public CustomerRefDto(Long id, String name) {
+    this.id = id;
+    this.name = name;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getName() {
+    return name;
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/ReverseSecretCipher.java

@@ -0,0 +1,14 @@
+package org.tests.dtomapping;
+
+/**
+ * Simple, deterministic (non-cryptographic) {@link SecretCipher} used purely to prove instance
+ * dispatch actually goes through the resolved instance (rather than being coincidentally
+ * static-callable) - reverses the encoded string.
+ */
+public final class ReverseSecretCipher implements SecretCipher {
+
+  @Override
+  public String decode(String encoded) {
+    return new StringBuilder(encoded).reverse().toString();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/SecretCipher.java

@@ -0,0 +1,12 @@
+package org.tests.dtomapping;
+
+/**
+ * Stand-in for a conversion needing a real dependency (e.g. {@code AES256Cipher}) - the
+ * {@code @DtoConvert} instance-dispatch case (requirement r14): an instance is resolved via
+ * {@code DtoConverterManager.get(SecretCipher.class)}, which must be registered (see
+ * {@link ContactConversionDbConfigProvider}) before the {@code Database} is built.
+ */
+public interface SecretCipher {
+
+  String decode(String encoded);
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestAddressDtoMapping.java

@@ -0,0 +1,47 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Isolated test for the generated {@code AddressDtoMapper} - validates it can be used standalone,
+ * independent of {@code CustomerDtoMapper}, confirming the per-type mapper composition approach.
+ * The mapper itself is generated by {@code querybean-generator} from the {@code @DtoMapping}
+ * registered in {@code package-info.java} - see docs/dto-mapping-design.md (requirement
+ * dto-codegen-mapper).
+ */
+class TestAddressDtoMapping {
+
+  private final AddressDtoMapper mapper = new AddressDtoMapper();
+
+  @Test
+  void mapAddress_expectFieldsCopied() {
+    Address address = new Address("12 Test Street", "Auckland");
+    address.save();
+
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+
+    Customer found = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .fetch("billingAddress", "id,line1,city")
+      .where().idEq(customer.getId())
+      .findOne();
+
+    AddressDto dto = mapper.map(found.getBillingAddress());
+
+    assertThat(dto.getId()).isEqualTo(address.getId());
+    assertThat(dto.getLine1()).isEqualTo(address.getLine1());
+    assertThat(dto.getCity()).isEqualTo(address.getCity());
+  }
+
+  @Test
+  void mapAddress_whenNull_expectNull() {
+    assertThat(mapper.map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestContactDtoGraphMapping.java

@@ -0,0 +1,75 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates the generated {@code ContactDtoMapper} standalone, and specifically the identity
+ * de-duplication behaviour of {@code io.ebean.DtoMapContext} (requirements r1/r3): several
+ * {@link Contact}s sharing the same parent {@link Customer} must map their {@code customer}
+ * back-reference to the exact same {@link CustomerRefDto} instance rather than each producing an
+ * equal-but-distinct copy.
+ * <p>
+ * {@link CustomerRefDto} exists (rather than reusing {@link CustomerDto}) so this back-reference
+ * doesn't reintroduce the {@code Customer -> Contact -> Customer} cycle.
+ */
+class TestContactDtoGraphMapping {
+
+  private final ContactDtoMapper mapper = new ContactDtoMapper();
+
+  @Test
+  void mapContacts_sharingSameCustomer_expectIdenticalCustomerRefInstance() {
+    Address address = new Address("1 High Street", "Wellington");
+    address.save();
+
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    new Contact("John", "Doe", customer).save();
+
+    Customer found = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .fetch("contacts", "id,firstName,lastName,active,customer")
+      .fetch("contacts.customer", "id,name")
+      .fetch("contacts.customer.billingAddress", "id,city")
+      .where().idEq(customer.getId())
+      .findOne();
+
+    List<Contact> contacts = found.getContacts();
+    assertThat(contacts.size()).isGreaterThan(1);
+
+    List<ContactDto> dtos = mapper.mapList(contacts);
+
+    assertThat(dtos).hasSameSizeAs(contacts);
+    for (int i = 0; i < dtos.size(); i++) {
+      assertThat(dtos.get(i).getFirstName()).isEqualTo(contacts.get(i).getFirstName());
+      // direct boolean scalar mapping - source's isActive() (not a guessed getActive())
+      assertThat(dtos.get(i).isActive()).isTrue();
+      assertThat(dtos.get(i).getCustomer().getId()).isEqualTo(customer.getId());
+      assertThat(dtos.get(i).getCustomer().getName()).isEqualTo(customer.getName());
+      // @DtoRef (id-only) and @DtoPath (multi-hop, through the customer association) properties
+      assertThat(dtos.get(i).getCustomerId()).isEqualTo(customer.getId());
+      assertThat(dtos.get(i).getCustomerCity()).isEqualTo("Wellington");
+    }
+
+    // identity de-dup: every contact's customer back-reference is the exact same DTO instance
+    CustomerRefDto first = dtos.get(0).getCustomer();
+    for (ContactDto dto : dtos) {
+      assertThat(dto.getCustomer()).isSameAs(first);
+    }
+  }
+
+  @Test
+  void mapContact_whenSourceNull_expectNullDto() {
+    assertThat(mapper.map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestContactStatsDtoMapping.java

@@ -0,0 +1,78 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.ContactStats;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Worked example: {@code @Sum}/{@code @Aggregation} group-by formulas modelled as a second
+ * {@code @Entity @View} read entity over the same {@code contact} table, mapped to a flat DTO.
+ * See docs/dto-mapping-design.md, "Aggregate/group-by computed properties".
+ */
+class TestContactStatsDtoMapping {
+
+  @Test
+  void mapContactStats_expectCountAndSumGroupedByCustomer() {
+    Customer customerA = new Customer("Quill Quarry");
+    customerA.save();
+    contact(customerA, "Ann", "Anders", 10);
+    contact(customerA, "Bert", "Baxter", 20);
+    contact(customerA, "Cleo", "Cross", 30);
+
+    Customer customerB = new Customer("Rill Ridge");
+    customerB.save();
+    contact(customerB, "Dom", "Dune", 5);
+    contact(customerB, "Eve", "Ellis", 15);
+
+    ContactStatsDto statsA = DB.find(ContactStats.class)
+      .where().eq("customer.id", customerA.getId())
+      .mapTo(ContactStatsDto.class)
+      .findOne();
+
+    assertThat(statsA).isNotNull();
+    assertThat(statsA.getCustomerId()).isEqualTo(customerA.getId());
+    assertThat(statsA.getContactCount()).isEqualTo(3);
+    assertThat(statsA.getEngagementScore()).isEqualTo(60);
+
+    ContactStatsDto statsB = DB.find(ContactStats.class)
+      .where().eq("customer.id", customerB.getId())
+      .mapTo(ContactStatsDto.class)
+      .findOne();
+
+    assertThat(statsB).isNotNull();
+    assertThat(statsB.getCustomerId()).isEqualTo(customerB.getId());
+    assertThat(statsB.getContactCount()).isEqualTo(2);
+    assertThat(statsB.getEngagementScore()).isEqualTo(20);
+  }
+
+  @Test
+  void mapContactStats_findList_expectOneRowPerCustomer() {
+    Customer customer = new Customer("Sable Springs");
+    customer.save();
+    contact(customer, "Fay", "Finch", 7);
+    contact(customer, "Gus", "Gray", 13);
+
+    List<ContactStatsDto> list = DB.find(ContactStats.class)
+      .where().eq("customer.id", customer.getId())
+      .mapTo(ContactStatsDto.class)
+      .findList();
+
+    assertThat(list).hasSize(1);
+    ContactStatsDto dto = list.get(0);
+    assertThat(dto.getCustomerId()).isEqualTo(customer.getId());
+    assertThat(dto.getContactCount()).isEqualTo(2);
+    assertThat(dto.getEngagementScore()).isEqualTo(20);
+  }
+
+  private void contact(Customer customer, String firstName, String lastName, int engagementScore) {
+    Contact contact = new Contact(firstName, lastName, customer);
+    contact.setEngagementScore(engagementScore);
+    contact.save();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestContactSummaryDtoMapping.java

@@ -0,0 +1,44 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.ContactSummary;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Worked example: a Blaze-Persistence-style computed DTO property ({@code fullName}) achieved
+ * via a {@code @View}-mapped read entity ({@link ContactSummary}, pointed at the same table as
+ * {@link Contact}) carrying a {@code @Formula2} computed property, mapped into a plain DTO
+ * ({@link ContactSummaryDto}) with the existing {@code @DtoMapping} machinery - no new
+ * ad-hoc-SQL-on-DTO annotation needed. See docs/dto-mapping-design.md, "Ad-hoc computed/formula
+ * properties: model as {@code @Entity @View}/{@code @Sql}, not ad-hoc SQL-on-DTO".
+ */
+class TestContactSummaryDtoMapping {
+
+  private final ContactSummaryDtoMapper mapper = new ContactSummaryDtoMapper();
+
+  @Test
+  void mapContactSummary_expectComputedFullName() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    new Contact("Zenith", "Zolton", customer).save();
+
+    ContactSummary summary = DB.find(ContactSummary.class)
+      .setUnmodifiable(true)
+      .where().eq("firstName", "Zenith").eq("lastName", "Zolton")
+      .findOne();
+
+    ContactSummaryDto dto = mapper.map(summary);
+
+    assertThat(dto.getId()).isEqualTo(summary.getId());
+    assertThat(dto.getFullName()).isEqualTo("Zenith Zolton");
+  }
+
+  @Test
+  void mapContactSummary_whenNull_expectNull() {
+    assertThat(mapper.map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestCustomerDtoGraphMapping.java

@@ -0,0 +1,97 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import io.ebean.LazyInitialisationException;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * End-to-end validation of the generated nested (ToOne + ToMany) DTO graph mapping for issue
+ * #2540 - the key milestone for requirement dto-codegen-mapper: {@code CustomerDtoMapper} (and
+ * its nested {@code AddressDtoMapper}/{@code ContactDtoMapper}/{@code CustomerRefDtoMapper}) are
+ * entirely generated by {@code querybean-generator} from the {@code @DtoMapping} declarations in
+ * {@code package-info.java} - no hand-written mapper code exists in this module.
+ */
+class TestCustomerDtoGraphMapping {
+
+  private final CustomerDtoMapper mapper = new CustomerDtoMapper();
+
+  @Test
+  void mapCustomerWithBillingAddress_whenFetched_expectPopulatedDto() {
+    Address address = new Address("12 Test Street", "Auckland");
+    address.save();
+
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    new Contact("John", "Doe", customer).save();
+
+    List<Customer> customers = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .fetch("billingAddress", "id,line1,city")
+      .fetch("contacts", "id,firstName,lastName,active,customer")
+      .fetch("contacts.customer", "id,name")
+      .fetch("contacts.customer.billingAddress", "id,city")
+      .where().idEq(customer.getId())
+      .findList();
+
+    List<CustomerDto> dtos = mapper.mapList(customers);
+
+    assertThat(dtos).hasSameSizeAs(customers);
+    for (int i = 0; i < dtos.size(); i++) {
+      Customer source = customers.get(i);
+      CustomerDto dto = dtos.get(i);
+
+      assertThat(dto.getId()).isEqualTo(source.getId());
+      assertThat(dto.getName()).isEqualTo(source.getName());
+
+      assertThat(dto.getBillingAddress().getId()).isEqualTo(source.getBillingAddress().getId());
+      assertThat(dto.getBillingAddress().getLine1()).isEqualTo(source.getBillingAddress().getLine1());
+      assertThat(dto.getBillingAddress().getCity()).isEqualTo(source.getBillingAddress().getCity());
+
+      assertThat(dto.getContacts()).hasSameSizeAs(source.getContacts());
+      for (int c = 0; c < dto.getContacts().size(); c++) {
+        assertThat(dto.getContacts().get(c).getFirstName()).isEqualTo(source.getContacts().get(c).getFirstName());
+        // the ToMany contact's back-reference resolves to the very same CustomerRefDto instance
+        // as every sibling contact under this customer - identity de-dup (requirement r3/r1)
+        assertThat(dto.getContacts().get(c).getCustomer().getId()).isEqualTo(dto.getId());
+      }
+      assertThat(dto.getContacts().get(0).getCustomer()).isSameAs(dto.getContacts().get(1).getCustomer());
+    }
+  }
+
+  @Test
+  void mapCustomer_whenBillingAddressNotFetched_expectFailFastNotSilentNullOrLazyLoad() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+
+    // deliberately does NOT fetch billingAddress - mismatch between DTO shape and query
+    Customer found = DB.find(Customer.class)
+      .setUnmodifiable(true)
+      .select("id,name")
+      .where().idEq(customer.getId())
+      .findOne();
+
+    // The generated mapper has no special-case handling for this - it just calls
+    // getBillingAddress(), which fails fast because the unmodifiable+disableLazyLoading graph
+    // refuses to silently lazy load or return null for an unloaded property. This is the
+    // fail-fast guarantee (requirement r7) coming "for free" out of the mapTo pipeline design.
+    assertThatThrownBy(() -> mapper.map(found))
+      .isInstanceOf(LazyInitialisationException.class)
+      .hasMessageContaining("Property not loaded: billingAddress");
+  }
+
+  @Test
+  void mapCustomer_whenSourceNull_expectNullDto() {
+    assertThat(mapper.map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoBuilderConstruction.java

@@ -0,0 +1,48 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates builder-based target construction (requirement r18, "Section G" in
+ * docs/dto-mapping-requirements.md) - {@link ContactBuilderDto} is registered with
+ * {@code @DtoMapping(builder = ALWAYS)}, forcing the generated {@code ContactBuilderDtoMapper} to
+ * construct the target via {@code ContactBuilderDto.builder()....build()} rather than a
+ * positional constructor.
+ */
+class TestDtoBuilderConstruction {
+
+  private final ContactBuilderDtoMapper mapper = new ContactBuilderDtoMapper();
+
+  @Test
+  void mapTo_expectBuilderConstructedDto() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.setStatus((short) 1);
+    contact.setSecretCode("shh");
+    contact.save();
+
+    ContactBuilderDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(ContactBuilderDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getId()).isEqualTo(contact.getId());
+    assertThat(dto.getFirstName()).isEqualTo("Jane");
+    assertThat(dto.getLastName()).isEqualTo("Doe");
+    assertThat(dto.getStatus()).isEqualTo((short) 1);
+    assertThat(dto.getSecretCode()).isEqualTo("shh");
+    assertThat(dto.getCustomerId()).isEqualTo(customer.getId());
+  }
+
+  @Test
+  void map_whenSourceNull_expectNullDto() {
+    assertThat(mapper.map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoConvert.java

@@ -0,0 +1,78 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import io.ebean.DtoConverterManager;
+import jakarta.persistence.PersistenceException;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Validates {@code @DtoConvert} (requirements r13/r14, "Section E: Custom property conversion"
+ * in docs/dto-mapping-requirements.md) - both static dispatch (no registration,
+ * {@link ContactConversions#toActive}) and instance dispatch (resolved via
+ * {@link DtoConverterManager}, {@link SecretCipher#decode}).
+ * <p>
+ * {@link SecretCipher} is registered by {@link ContactConversionDbConfigProvider} (a
+ * {@code DatabaseConfigProvider}, discovered via ServiceLoader before the {@code Database} is
+ * built) rather than in a test {@code @BeforeAll} - {@code EbeanDtoMapperRegister}'s mapper
+ * fields (including {@code ContactConversionDtoMapper}'s {@code SecretCipher} field) are all
+ * constructed eagerly during {@code Database} startup, which can be triggered by whichever test
+ * class in this module happens to run first.
+ */
+class TestDtoConvert {
+
+  @Test
+  void mapTo_expectStaticAndInstanceConversionsApplied() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.setStatus((short) 1);
+    contact.setSecretCode("terces");
+    contact.save();
+
+    ContactConversionDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(ContactConversionDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getFirstName()).isEqualTo("Jane");
+    // static dispatch - Short(1) -> true, no registration needed
+    assertThat(dto.isActive()).isTrue();
+    // instance dispatch - resolved via DtoConverterManager, ReverseSecretCipher reverses the string
+    assertThat(dto.getSecretCode()).isEqualTo("secret");
+  }
+
+  @Test
+  void mapTo_whenStatusZero_expectInactive() {
+    Customer customer = new Customer("Beta");
+    customer.save();
+    Contact contact = new Contact("John", "Smith", customer);
+    contact.setStatus((short) 0);
+    contact.setSecretCode("abc");
+    contact.save();
+
+    ContactConversionDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(ContactConversionDto.class)
+      .findOne();
+
+    assertThat(dto.isActive()).isFalse();
+  }
+
+  @Test
+  void get_whenTypeNotRegistered_expectPersistenceException() {
+    assertThatThrownBy(() -> DtoConverterManager.get(UnregisteredConverter.class))
+      .isInstanceOf(PersistenceException.class)
+      .hasMessageContaining("No " + UnregisteredConverter.class.getName() + " registered")
+      .hasMessageContaining("DtoConverterManager.put(UnregisteredConverter.class, ...)");
+  }
+
+  /** Deliberately never registered with {@link DtoConverterManager} - used to prove {@link DtoConverterManager#get} fails fast. */
+  private interface UnregisteredConverter {
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoMapperManager.java

@@ -0,0 +1,61 @@
+package org.tests.dtomapping;
+
+import io.ebean.DtoMapper;
+import io.ebean.DtoMapperManager;
+import io.ebean.DtoConverterManager;
+import jakarta.persistence.PersistenceException;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * {@link DtoMapperManager} has no dependency on {@code Database} - its constructor only does
+ * {@code ServiceLoader} discovery of generated {@code DtoMapperRegister}s - so it can be
+ * constructed standalone, independent of (or before) any {@code Database}.
+ * <p>
+ * A standalone construction like this bypasses the {@code DatabaseConfigProvider} hook (that
+ * hook is specifically about {@code Database} startup ordering) - so any {@code @DtoConvert}
+ * instance-dispatch converter this module's mappers need (here, {@link SecretCipher}) must
+ * already be registered via {@link DtoConverterManager#put} by the application itself before
+ * constructing its own {@code DtoMapperManager}, exactly as it would before building a
+ * {@code Database}.
+ */
+class TestDtoMapperManager {
+
+  private final DtoMapperManager manager = manager();
+
+  private static DtoMapperManager manager() {
+    DtoConverterManager.put(SecretCipher.class, new ReverseSecretCipher());
+    return new DtoMapperManager();
+  }
+
+  @Test
+  void get_byMapperType_returnsTheGeneratedMapperInstance() {
+    CustomerDtoMapper mapper = manager.get(CustomerDtoMapper.class);
+
+    assertThat(mapper).isNotNull();
+    // repeated lookups return the exact same cached instance
+    assertThat(manager.get(CustomerDtoMapper.class)).isSameAs(mapper);
+  }
+
+  @Test
+  void get_andMapperFor_resolveToTheSameUnderlyingMapperInstance() {
+    CustomerDtoMapper byType = manager.get(CustomerDtoMapper.class);
+    DtoMapper<Customer, CustomerDto> byPair = manager.mapperFor(Customer.class, CustomerDto.class);
+
+    assertThat(byType).isSameAs(byPair);
+  }
+
+  @Test
+  void get_whenMapperTypeNotRegistered_expectPersistenceException() {
+    assertThatThrownBy(() -> manager.get(UnregisteredMapper.class))
+      .isInstanceOf(PersistenceException.class)
+      .hasMessageContaining("No DtoMapper of type " + UnregisteredMapper.class.getName() + " registered");
+  }
+
+  /** Deliberately never generated - used to prove {@link DtoMapperManager#get} fails fast. */
+  private interface UnregisteredMapper {
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoMapperManagerSharing.java

@@ -0,0 +1,82 @@
+package org.tests.dtomapping;
+
+import io.ebean.Database;
+import io.ebean.DatabaseBuilder;
+import io.ebean.DtoConverterManager;
+import io.ebean.DtoMapperManager;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.Properties;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates that {@link DtoMapperManager} can be constructed independently of any {@code
+ * Database} (its constructor only does {@code ServiceLoader} discovery of generated {@code
+ * DtoMapperRegister}s) and, once registered via {@code
+ * DatabaseBuilder.putServiceObject(DtoMapperManager.class, ...)} before {@code build()}, is the
+ * instance actually used internally by {@code query.mapTo(...)} - so the very same instance is
+ * also directly usable elsewhere, e.g. wired up for constructor injection into application
+ * services (replacing hand-written mapper wiring like {@code DriverMapper}/{@code DriverService}
+ * in the motivating central-access example).
+ */
+class TestDtoMapperManagerSharing {
+
+  @Test
+  void putServiceObject_sharesSameManagerInstance_betweenMapToAndDirectInjection() {
+    // a standalone construction bypasses the DatabaseConfigProvider hook, so this module's
+    // @DtoConvert instance-dispatch converter must already be registered - see TestDtoMapperManager
+    DtoConverterManager.put(SecretCipher.class, new ReverseSecretCipher());
+    DtoMapperManager sharedManager = new DtoMapperManager();
+
+    Database db = buildSecondaryDatabase(sharedManager);
+    try {
+      Customer customer = new Customer("Acme");
+      db.save(customer);
+
+      // query.mapTo(...) against this secondary Database resolves via the supplied manager
+      CustomerDto dto = db.find(Customer.class)
+        .where().idEq(customer.getId())
+        .mapTo(CustomerDto.class)
+        .findOne();
+
+      assertThat(dto).isNotNull();
+      assertThat(dto.getName()).isEqualTo("Acme");
+
+      // the exact same manager instance we passed into putServiceObject resolves the same
+      // generated mapper by its own concrete type - directly usable for e.g. constructor
+      // injection into application services, independent of query.mapTo()
+      CustomerDtoMapper mapper = sharedManager.get(CustomerDtoMapper.class);
+      assertThat(mapper.map(customer).getName()).isEqualTo("Acme");
+    } finally {
+      db.shutdown();
+    }
+  }
+
+  private static Database buildSecondaryDatabase(DtoMapperManager sharedManager) {
+    DatabaseBuilder config = Database.builder();
+    config.setName("dtoMapperManagerSharing");
+    config.setRegister(false);
+    config.setDefaultServer(false);
+    config.setDdlGenerate(true);
+    config.setDdlRun(true);
+    config.setDdlExtra(false);
+
+    Properties properties = new Properties();
+    properties.setProperty("datasource.dtoMapperManagerSharing.username", "sa");
+    properties.setProperty("datasource.dtoMapperManagerSharing.password", "");
+    properties.setProperty("datasource.dtoMapperManagerSharing.databaseUrl", "jdbc:h2:mem:dtoMapperManagerSharing");
+    properties.setProperty("datasource.dtoMapperManagerSharing.databaseDriver", "org.h2.Driver");
+    config.loadFromProperties(properties);
+
+    config.addClass(Customer.class);
+    config.addClass(Contact.class);
+    config.addClass(Address.class);
+
+    config.putServiceObject(DtoMapperManager.class, sharedManager);
+    return config.build();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoMapperRegister.java

@@ -0,0 +1,53 @@
+package org.tests.dtomapping;
+
+import io.ebean.DtoMapper;
+import io.ebean.config.DtoMapperRegister;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.ServiceLoader;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates the generated {@code EbeanDtoMapperRegister} is discoverable via
+ * {@code META-INF/services/io.ebean.config.DtoMapperRegister} and correctly dispatches on the
+ * (source, target) pair - see docs/dto-mapping-design.md (requirement dto-codegen-mapper).
+ */
+class TestDtoMapperRegister {
+
+  private final DtoMapperRegister register = ServiceLoader.load(DtoMapperRegister.class)
+    .findFirst()
+    .orElseThrow(() -> new IllegalStateException("No DtoMapperRegister found via ServiceLoader"));
+
+  @Test
+  void mapperFor_whenSourceAndTargetMatch_expectMapper() {
+    DtoMapper<Customer, CustomerDto> mapper = register.mapperFor(Customer.class, CustomerDto.class);
+
+    assertThat(mapper).isInstanceOf(CustomerDtoMapper.class);
+  }
+
+  @Test
+  void mapperFor_whenDifferentTargetForSameSource_expectDifferentMapper() {
+    DtoMapper<Customer, CustomerRefDto> refMapper = register.mapperFor(Customer.class, CustomerRefDto.class);
+
+    assertThat(refMapper).isInstanceOf(CustomerRefDtoMapper.class);
+  }
+
+  @Test
+  void mapperFor_whenSourceDoesNotMatchTarget_expectNull() {
+    // CustomerDto only maps from Customer, not Contact - so this pair is unregistered.
+    DtoMapper<Contact, CustomerDto> mapper = register.mapperFor(Contact.class, CustomerDto.class);
+
+    assertThat(mapper).isNull();
+  }
+
+  @Test
+  void mapperFor_whenUnregisteredPair_expectNull() {
+    DtoMapper<Address, CustomerDto> mapper = register.mapperFor(Address.class, CustomerDto.class);
+
+    assertThat(mapper).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoMapperVariants.java

@@ -0,0 +1,72 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates named mapper variants (requirement r19, "Section G" in
+ * docs/dto-mapping-requirements.md) - {@code CustomerDto} is registered twice: the base mapping,
+ * plus {@code @DtoMapping(name = "noContacts", exclude = "contacts")}. Both share the very same
+ * generated {@code CustomerDtoMapper} class; the variant is exposed as its {@code noContacts()}
+ * accessor and selected via the {@code query.mapTo(Class, DtoMapper)} overload (requirement
+ * r19's API addition) rather than a string-based lookup.
+ */
+class TestDtoMapperVariants {
+
+  private final CustomerDtoMapper mapper = new CustomerDtoMapper();
+
+  @Test
+  void mapTo_withNoContactsVariant_expectContactsExcludedButAddressPopulated() {
+    Address address = new Address("12 Test Street", "Auckland");
+    address.save();
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+
+    CustomerDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class, mapper.noContacts())
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getId()).isEqualTo(customer.getId());
+    assertThat(dto.getName()).isEqualTo("Acme");
+    // billingAddress is NOT excluded by this variant - still populated
+    assertThat(dto.getBillingAddress()).isNotNull();
+    assertThat(dto.getBillingAddress().getCity()).isEqualTo("Auckland");
+    // contacts IS excluded by this variant - empty, not null, and no fetch/join issued for it
+    assertThat(dto.getContacts()).isEmpty();
+  }
+
+  @Test
+  void mapTo_baseMapping_expectContactsStillPopulated() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    new Contact("John", "Doe", customer).save();
+
+    CustomerDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class)
+      .findOne();
+
+    assertThat(dto.getContacts()).hasSize(2);
+  }
+
+  @Test
+  void noContacts_expectOwnFetchGroupOmitsContactsFetch() {
+    assertThat(mapper.noContacts().fetchGroup()).isNotNull();
+    assertThat(mapper.fetchGroup()).isNotSameAs(mapper.noContacts().fetchGroup());
+  }
+
+  @Test
+  void noContacts_whenSourceNull_expectNullDto() {
+    assertThat(mapper.noContacts().map(null)).isNull();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestDtoMixin.java

@@ -0,0 +1,59 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Validates {@code @DtoMixin} - overlaying {@code @DtoPath}/{@code @DtoConvert} annotations from
+ * {@link ContactMixinDtoMixin} onto {@link ContactMixinDto}, which carries no annotations of its
+ * own at all (a stand-in for a DTO generated elsewhere, e.g. from an OpenAPI spec).
+ */
+class TestDtoMixin {
+
+  @Test
+  void mapTo_expectMixinAnnotationsApplied() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.setStatus((short) 1);
+    contact.setSecretCode("terces");
+    contact.save();
+
+    ContactMixinDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(ContactMixinDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getFirstName()).isEqualTo("Jane");
+    // @DtoPath("status") + static @DtoConvert, both declared on the mixin method
+    assertThat(dto.isActive()).isTrue();
+    // instance @DtoConvert declared on the mixin method, resolved via DtoConverterManager
+    assertThat(dto.getSecretCode()).isEqualTo("secret");
+    // @DtoPath("customer") rename on the mixin, resolving to the nested CustomerRefDto mapper
+    // rather than a raw (type-mismatched) scalar getter call
+    assertThat(dto.getOwner()).isNotNull();
+    assertThat(dto.getOwner().getName()).isEqualTo("Acme");
+  }
+
+  @Test
+  void mapTo_whenStatusZero_expectInactive() {
+    Customer customer = new Customer("Beta");
+    customer.save();
+    Contact contact = new Contact("John", "Smith", customer);
+    contact.setStatus((short) 0);
+    contact.setSecretCode("abc");
+    contact.save();
+
+    ContactMixinDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(ContactMixinDto.class)
+      .findOne();
+
+    assertThat(dto.isActive()).isFalse();
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestMapperManualUsage.java

@@ -0,0 +1,81 @@
+package org.tests.dtomapping;
+
+import io.ebean.DtoMapContext;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Every generated {@code XxxDtoMapper} is a plain public class - a public no-arg constructor
+ * (or an explicit constructor taking its nested-mapper/converter dependencies) and a public
+ * {@code map(...)}/{@code mapList(...)} - so it can be called directly, without going through
+ * {@code query.mapTo()} at all. This is useful both as a normal API (map an entity graph you
+ * already have on hand, from wherever it came from) and for fast, isolated unit tests of the
+ * mapping logic itself - construct plain entities, call the mapper, assert on the DTO, with no
+ * query execution and no {@code DtoMapperManager}/{@code ServiceLoader} registry involved.
+ * <p>
+ * See also {@link TestCustomerDtoGraphMapping}, which does the same thing against a manually run
+ * (non-{@code mapTo}) query.
+ */
+class TestMapperManualUsage {
+
+  @Test
+  void map_directlyOnEntitiesJustCreated_withoutQueryOrMapTo() {
+    Address address = new Address("1 Queen Street", "Auckland");
+    address.save();
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.save();
+    customer.getContacts().add(contact);
+
+    // the very same in-memory objects just saved - no DB.find()/mapTo() query at all
+    CustomerDto dto = new CustomerDtoMapper().map(customer);
+
+    assertThat(dto.getName()).isEqualTo("Acme");
+    assertThat(dto.getBillingAddress().getCity()).isEqualTo("Auckland");
+    assertThat(dto.getContacts()).hasSize(1);
+    assertThat(dto.getContacts().get(0).getFirstName()).isEqualTo("Jane");
+  }
+
+  @Test
+  void mapList_sharedContext_identityDedupWithoutMapTo() {
+    Customer customer = new Customer("Acme");
+    customer.save();
+    Contact jane = new Contact("Jane", "Doe", customer);
+    jane.save();
+    Contact john = new Contact("John", "Doe", customer);
+    john.save();
+
+    DtoMapContext context = new DtoMapContext();
+    List<ContactDto> dtos = new ContactDtoMapper().mapList(List.of(jane, john), context);
+
+    // both contacts share the same Customer instance - mapped via the same shared context - so
+    // the nested CustomerRefDto instance is de-duplicated (same reference, not just equal)
+    assertThat(dtos.get(0).getCustomer()).isSameAs(dtos.get(1).getCustomer());
+  }
+
+  @Test
+  void map_withTestDoubleConverter_bypassingDtoConverterManager() {
+    // the explicit constructor lets a test pass its own SecretCipher directly - no need to
+    // register anything with DtoConverterManager for this kind of isolated unit test
+    SecretCipher upperCasingTestCipher = String::toUpperCase;
+    Customer customer = new Customer("Acme");
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.setStatus((short) 1);
+    contact.setSecretCode("shh");
+    contact.save();
+
+    ContactConversionDto dto = new ContactConversionDtoMapper(upperCasingTestCipher).map(contact);
+
+    assertThat(dto.isActive()).isTrue();
+    assertThat(dto.getSecretCode()).isEqualTo("SHH");
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/TestQueryMapTo.java

@@ -0,0 +1,264 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import io.ebean.LazyInitialisationException;
+import io.ebean.PagedList;
+import io.ebean.Transaction;
+import io.ebean.test.LoggedSql;
+import jakarta.persistence.PersistenceException;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.Customer;
+import org.tests.dtomapping.model.query.QCustomer;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * End-to-end validation of {@code query.mapTo(Dto.class)} - the full-scope runtime wiring for
+ * issue #2540. Unlike {@link TestCustomerDtoGraphMapping} (which calls the generated mapper
+ * directly against a manually fetched entity graph), these tests exercise the entire pipeline:
+ * resolving the generated {@code DtoMapper} via {@code ServiceLoader}, automatically applying its
+ * {@code fetchGroup()} (derived from the DTO's declared shape - no manual {@code .select()}/
+ * {@code .fetch()} needed), forcing {@code setUnmodifiable(true)}, then mapping the result.
+ */
+class TestQueryMapTo {
+
+  @Test
+  void mapTo_findList_expectAutoFetchSpecAppliedAndPopulatedDtoGraph() {
+    Address address = new Address("12 Test Street", "Auckland");
+    address.save();
+
+    Customer customer = new Customer("Acme");
+    customer.setBillingAddress(address);
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    new Contact("John", "Doe", customer).save();
+
+    // no .select()/.fetch() at all - the fetch spec is derived from CustomerDto's shape
+    List<CustomerDto> dtos = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class)
+      .findList();
+
+    assertThat(dtos).hasSize(1);
+    CustomerDto dto = dtos.get(0);
+    assertThat(dto.getId()).isEqualTo(customer.getId());
+    assertThat(dto.getName()).isEqualTo("Acme");
+    assertThat(dto.getBillingAddress().getLine1()).isEqualTo("12 Test Street");
+    assertThat(dto.getBillingAddress().getCity()).isEqualTo("Auckland");
+    assertThat(dto.getContacts()).hasSize(2);
+    assertThat(dto.getContacts().get(0).getCustomer()).isSameAs(dto.getContacts().get(1).getCustomer());
+    // @DtoRef (id-only) and @DtoPath (multi-hop) properties on ContactDto
+    assertThat(dto.getContacts().get(0).getCustomerId()).isEqualTo(customer.getId());
+    assertThat(dto.getContacts().get(0).getCustomerCity()).isEqualTo("Auckland");
+  }
+
+  @Test
+  void mapTo_findOne_expectPopulatedDto() {
+    Customer customer = new Customer("Beta");
+    customer.save();
+
+    CustomerDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getName()).isEqualTo("Beta");
+  }
+
+  @Test
+  void mapTo_findOneOrEmpty_whenNoMatch_expectEmpty() {
+    Optional<CustomerDto> dto = new QCustomer()
+      .id.eq(-1L)
+      .mapTo(CustomerDto.class)
+      .findOneOrEmpty();
+
+    assertThat(dto).isEmpty();
+  }
+
+  @Test
+  void mapTo_whenPairNotRegistered_expectPersistenceException() {
+    assertThatThrownBy(() -> DB.find(Contact.class).mapTo(CustomerDto.class).findList())
+      .isInstanceOf(PersistenceException.class)
+      .hasMessageContaining("No DtoMapper registered");
+  }
+
+  @Test
+  void mapTo_findPagedList_expectPagedMappedDtos() {
+    new Customer("PageA").save();
+    new Customer("PageB").save();
+    new Customer("PageC").save();
+
+    PagedList<CustomerDto> paged = DB.find(Customer.class)
+      .where().startsWith("name", "Page")
+      .orderBy().asc("name")
+      .setFirstRow(0)
+      .setMaxRows(2)
+      .mapTo(CustomerDto.class)
+      .findPagedList();
+
+    assertThat(paged.getTotalCount()).isEqualTo(3);
+    assertThat(paged.hasNext()).isTrue();
+    assertThat(paged.hasPrev()).isFalse();
+    List<CustomerDto> page1 = paged.getList();
+    assertThat(page1).extracting(CustomerDto::getName).containsExactly("PageA", "PageB");
+    // getList() is cached - same instance on repeated calls
+    assertThat(paged.getList()).isSameAs(page1);
+  }
+
+  @Test
+  void mapTo_whenSelectAlreadySet_expectManualFetchSpecPreserved() {
+    Address address = new Address("1 Manual Street", "Wellington");
+    address.save();
+
+    Customer customer = new Customer("ManualSelect");
+    customer.setBillingAddress(address);
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+
+    LoggedSql.start();
+    // manually tuned select() - deliberately narrower than CustomerDto's own fetch spec
+    // (excludes billingAddress and contacts) - this should be left untouched by mapTo()
+    var query = DB.find(Customer.class)
+      .select("name")
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class);
+
+    // mapper.fetchGroup() was NOT merged over the top of the manual select() - so mapping
+    // billingAddress (not fetched) fails fast rather than silently lazy loading it
+    assertThatThrownBy(query::findList)
+      .isInstanceOf(LazyInitialisationException.class)
+      .hasMessageContaining("billingAddress");
+
+    List<String> sql = LoggedSql.stop();
+    // only the manually selected properties were fetched - no join to address
+    assertThat(sql).hasSize(1);
+    assertThat(sql.get(0)).doesNotContain("o_address");
+  }
+
+  @Test
+  void mapTo_usingMaster_expectFluentReturnAndNoError() {
+    Customer customer = new Customer("MasterCo");
+    customer.save();
+
+    // usingMaster() can be called on the MappedQuery itself - e.g. on retry after a read-replica
+    // failure - without needing to rebuild the underlying query and call mapTo() again
+    var mapped = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class);
+
+    assertThat(mapped.usingMaster(false)).isSameAs(mapped);
+    assertThat(mapped.usingMaster(true)).isSameAs(mapped);
+
+    List<CustomerDto> dtos = mapped.findList();
+    assertThat(dtos).hasSize(1);
+    assertThat(dtos.get(0).getName()).isEqualTo("MasterCo");
+  }
+
+  @Test
+  void mapTo_usingTransaction_expectQueryRunsOnExplicitTransaction() {
+    Customer customer = new Customer("TxnCo");
+    customer.save();
+
+    try (Transaction txn = DB.beginTransaction()) {
+      List<CustomerDto> dtos = DB.find(Customer.class)
+        .where().idEq(customer.getId())
+        .mapTo(CustomerDto.class)
+        .usingTransaction(txn)
+        .findList();
+
+      assertThat(dtos).hasSize(1);
+      assertThat(dtos.get(0).getName()).isEqualTo("TxnCo");
+      txn.commit();
+    }
+  }
+
+  @Test
+  void mapTo_usingConnection_expectFluentReturn() {
+    Customer customer = new Customer("ConnCo");
+    customer.save();
+
+    try (Transaction txn = DB.beginTransaction()) {
+      var mapped = DB.find(Customer.class)
+        .where().idEq(customer.getId())
+        .mapTo(CustomerDto.class);
+
+      assertThat(mapped.usingConnection(txn.connection())).isSameAs(mapped);
+
+      List<CustomerDto> dtos = mapped.findList();
+      assertThat(dtos).hasSize(1);
+      assertThat(dtos.get(0).getName()).isEqualTo("ConnCo");
+    }
+  }
+
+  @Test
+  void mapTo_findStream_expectLazilyMappedDtoStream() {
+    Customer customerA = new Customer("StreamCoA");
+    customerA.save();
+    Customer customerB = new Customer("StreamCoB");
+    customerB.save();
+
+    List<String> names;
+    try (var stream = DB.find(Customer.class)
+      .where().in("name", "StreamCoA", "StreamCoB")
+      .orderBy().asc("name")
+      .mapTo(CustomerDto.class)
+      .findStream()) {
+      names = stream.map(CustomerDto::getName).collect(Collectors.toList());
+    }
+
+    assertThat(names).containsExactly("StreamCoA", "StreamCoB");
+  }
+
+  @Test
+  void mapTo_findStream_expectIdentityDedupSharedAcrossStream() {
+    Customer customer = new Customer("StreamDedupCo");
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    new Contact("John", "Doe", customer).save();
+
+    // both contacts share the same underlying Customer instance - the shared DtoMapContext used
+    // across the whole findStream() call should still de-duplicate to the same nested DTO
+    List<ContactDto> dtos;
+    try (var stream = DB.find(Contact.class)
+      .where().eq("customer", customer)
+      .orderBy().asc("firstName")
+      .mapTo(ContactDto.class)
+      .findStream()) {
+      dtos = stream.collect(Collectors.toList());
+    }
+
+    assertThat(dtos).hasSize(2);
+    assertThat(dtos.get(0).getCustomer()).isSameAs(dtos.get(1).getCustomer());
+  }
+
+  @Test
+  void mapTo_withFilterMany_expectFilteredContactsInDtoGraph() {
+    Customer customer = new Customer("FilterManyCo");
+    customer.save();
+    new Contact("Jane", "Doe", customer).save();
+    Contact inactive = new Contact("John", "Doe", customer);
+    inactive.setActive(false);
+    inactive.save();
+
+    // filterMany() combined with the DTO mapper's auto-applied fetchGroup() - contacts is part
+    // of CustomerDto's own fetch spec, filterMany() narrows the rows fetched for that relationship
+    List<CustomerDto> dtos = DB.find(Customer.class)
+      .filterMany("contacts").eq("active", true)
+      .where().idEq(customer.getId())
+      .mapTo(CustomerDto.class)
+      .findList();
+
+    assertThat(dtos).hasSize(1);
+    CustomerDto dto = dtos.get(0);
+    assertThat(dto.getContacts()).hasSize(1);
+    assertThat(dto.getContacts().get(0).getFirstName()).isEqualTo("Jane");
+  }
+}

tests/test-dto-mapping/src/test/java/org/tests/dtomapping/package-info.java

@@ -0,0 +1,60 @@
+/**
+ * Registers the DTO mapping pairs for issue #2540's nested DTO mapping - triggers
+ * {@code querybean-generator} to generate a {@code XxxMapper} implementing
+ * {@code io.ebean.DtoMapper<Source, Target>} for each pair (see docs/dto-mapping-design.md).
+ * <p>
+ * {@code Customer -> CustomerRefDto} is a second, shallow mapping for {@code Customer} (in
+ * addition to the full {@code Customer -> CustomerDto} mapping) - it's what {@link
+ * org.tests.dtomapping.ContactDto#getCustomer()} maps to, so the back-reference doesn't
+ * reintroduce the {@code Customer -> Contact -> Customer} cycle that a full nested {@code
+ * CustomerDto} would create.
+ * <p>
+ * {@code ContactSummary -> ContactSummaryDto} is a worked example (see docs/dto-mapping-design.md,
+ * "Ad-hoc computed/formula properties") of the recommended pattern for a Blaze-Persistence-style
+ * computed DTO property: {@code ContactSummary} is a {@code @View}-mapped read entity (pointed at
+ * the plain {@code contact} table, no new DDL) with a {@code @Formula2}-computed {@code fullName}
+ * property, mapped to a plain DTO with no new ad-hoc-SQL-on-DTO annotation required.
+ * <p>
+ * {@code ContactStats -> ContactStatsDto} is a worked example (see docs/dto-mapping-design.md,
+ * "Aggregate/group-by computed properties") of the same {@code @View} pattern applied to Ebean's
+ * {@code @Sum}/{@code @Aggregation} group-by formulas - the Blaze-Persistence parallel being an
+ * {@code @EntityView} with {@code @Mapping("SIZE(...)")}/{@code @Mapping("SUM(...)")} correlated
+ * mappings.
+ * <p>
+ * {@code Contact -> ContactConversionDto} exercises {@code @DtoConvert} (requirements r13/r14,
+ * "Section E: Custom property conversion" in docs/dto-mapping-requirements.md) - both the
+ * static-dispatch (no registration) and instance-dispatch (via {@code DtoConverterManager}) cases.
+ * <p>
+ * {@code Contact -> ContactMixinDto} exercises {@code @DtoMixin} - {@link
+ * org.tests.dtomapping.ContactMixinDto} carries no annotations of its own at all;
+ * {@link org.tests.dtomapping.ContactMixinDtoMixin} overlays the {@code @DtoPath}/
+ * {@code @DtoConvert} annotations instead.
+ * <p>
+ * {@code Customer -> CustomerDto, name = "noContacts", exclude = "contacts"} exercises named
+ * variants (requirement r19) - a second, differently-shaped mapping sharing the very same
+ * generated {@code CustomerDtoMapper} class, exposed as its {@code noContacts()} accessor method,
+ * used via the new {@code query.mapTo(Class, DtoMapper)} overload.
+ * <p>
+ * {@code Contact -> ContactBuilderDto} exercises builder-based construction (requirement r18) -
+ * {@link org.tests.dtomapping.ContactBuilderDto} follows the {@code avaje-recordbuilder}
+ * convention (a static {@code builder()} factory + fluent setters + {@code build()}), forced via
+ * {@code builder = ALWAYS}.
+ */
+@DtoMapping(source = Customer.class, target = CustomerDto.class)
+@DtoMapping(source = Customer.class, target = CustomerDto.class, name = "noContacts", exclude = "contacts")
+@DtoMapping(source = Address.class, target = AddressDto.class)
+@DtoMapping(source = Contact.class, target = ContactDto.class)
+@DtoMapping(source = Customer.class, target = CustomerRefDto.class)
+@DtoMapping(source = ContactSummary.class, target = ContactSummaryDto.class)
+@DtoMapping(source = ContactStats.class, target = ContactStatsDto.class)
+@DtoMapping(source = Contact.class, target = ContactConversionDto.class)
+@DtoMapping(source = Contact.class, target = ContactMixinDto.class)
+@DtoMapping(source = Contact.class, target = ContactBuilderDto.class, builder = DtoMapping.Builder.ALWAYS)
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoMapping;
+import org.tests.dtomapping.model.Address;
+import org.tests.dtomapping.model.Contact;
+import org.tests.dtomapping.model.ContactStats;
+import org.tests.dtomapping.model.ContactSummary;
+import org.tests.dtomapping.model.Customer;

tests/test-dto-mapping/src/test/resources/META-INF/services/io.ebean.config.DatabaseConfigProvider

@@ -0,0 +1 @@
+org.tests.dtomapping.ContactConversionDbConfigProvider