dto mapping: add some negative tests

Fix #2 — @DtoRef never checked hasField(): Added requires() to @DtoRef
 (same explicit-empty semantics as @DtoPath). DtoMappingReader now
 detects a computed association getter and requires an explicit
 requires(); DtoMapperWriter's REF case routes computed segments
 through extraFetchPaths instead of a broken select(assoc).

Fix #3 — requires() values never validated: Added DtoMappingReader.validateRequiresPath(...), walking every requires() segment against the real property graph (with List unwrapping via a new getterReturnTypeMirror helper). A typo now fails at compile time instead of resurfacing as a runtime PersistenceException. New negative

Fix #4 — bare requires() fetch vs narrowed sibling @DtoPath fetch collision: Traced into Ebean's OrmQueryDetail.fetch(...) and confirmed same-path fetch calls replace, not merge (Map.put). The old dedup logic had priority backwards, silently letting a narrow selection win and drop a computed getter's real dependency. Fixed by prioritizing the full fetch. Proved the regression test was meaningful by reverting the fix and confirming it fails with LazyInitialisationException: Property not loaded: line1, then restored the fix and confirmed it passes.

composites/ebean-clickhouse/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-clickhouse</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-cockroach/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-db2/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-db2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-h2/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-hana/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-hana</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-mariadb/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-mariadb</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-mysql/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-mysql</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-net-postgis/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -22,13 +22,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -47,19 +47,19 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-net-postgis-types</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

composites/ebean-nuodb/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-nuodb</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-oracle/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-oracle</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-pgvector/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -22,13 +22,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -47,19 +47,19 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-pgvector-types</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

composites/ebean-postgis/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -22,13 +22,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -47,19 +47,19 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-postgis-types</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

composites/ebean-postgres/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-sqlite/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlite</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-sqlserver/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlserver</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean-yugabyte/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -42,13 +42,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/ebean/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -17,13 +17,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -41,7 +41,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-jackson-mapper</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -60,13 +60,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-all</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

composites/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>composites</artifactId>

docs/dto-mapping-design.md

@@ -136,8 +136,31 @@ already recognise, which is worth spelling out explicitly so it's easy to "grok
   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`
+**Bug found and fixed (validation phase, testing against `central-access`): primitive-typed field +
+nullable intermediate hop = unboxing `NullPointerException`.** A multi-hop `@DtoPath` (or `@DtoRef`,
+which is always 2-hop) null-guards each intermediate getter with a ternary, e.g.
+`(source.getOrganisation() == null ? null : source.getOrganisation().getId())`. That ternary's static
+type is always the boxed wrapper (`Long`), since one branch is the `null` literal - fine when the DTO
+field is itself a reference type (`Long organisationId`), but when the DTO field is a **primitive**
+(`long organisationId`), passing that boxed expression to the constructor auto-unboxes it, throwing an
+unhelpful `NullPointerException` at runtime whenever the relation really is `null`. This compiled clean
+and only failed at runtime with real (nullable) production data - exactly the kind of gap a hand-written
+mapper would defensively guard against (e.g. `cEbox.getOrganisation() == null ? 0 : ...getId()`) but
+generated code didn't.
 
+Fixed in the generator: when a multi-hop `SCALAR`/`REF` property's DTO field type is primitive, the
+whole null-guarded chain is now wrapped in a small runtime helper (`io.ebean.DtoMapperSupport`) that
+resolves it safely:
+- **Default** (`@DtoPath` with no `failOnNull`, or any `@DtoRef`): silently defaults to the primitive's
+  zero-equivalent value (`0`/`false`/etc.) - matches the old hand-written-mapper convention.
+- **`@DtoPath(failOnNull = true)`**: throws a clear `IllegalStateException` naming the offending property
+  path instead, for callers who'd rather fail fast than silently mask a null they don't expect.
+
+`@DtoRef` has no `failOnNull` attribute (it has no other attributes at all) - it always uses the
+default (silent zero) behaviour. See `PrimitiveNullPathDto`/`PrimitiveNullPathFailOnNullDto` /
+`TestPrimitiveNullPath` for regression coverage.
+
+### 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
@@ -701,6 +724,264 @@ callers must consume it via try-with-resources to ensure the underlying resource
     `DtoConverterManager`) are all constructed eagerly during `Database` startup, which can be
     triggered by whichever test class in the module happens to run first.
 
+- **Fixed (validation phase, found via `central-access`): `@DtoPath` through a computed/derived
+  getter now fails at compile time, with an explicit `requires()` escape hatch.** `@DtoPath`
+  assumes every dotted segment names a real, fetchable Ebean bean property - so a path like
+  `@DtoPath("currentMachine.organisationMachine.registrationPlate")`, where `getOrganisationMachine()`
+  is a hand-written derived getter (not a real relation/column), used to **compile cleanly** (the
+  codegen had no way to tell it apart from a real property from source alone) but **fail at
+  runtime** with a `PersistenceException: No property found for [organisationMachine] in
+  expression ...`, because the generated `FetchGroup` builder tried to `fetch`/`select` it as if it
+  were a real Ebean property.
+  - Two genuinely separate sub-problems: (1) *detecting* that a path segment isn't a real,
+    fetchable property - solvable at compile time, since a real persistent property always has a
+    backing field (Ebean requires one to enhance), checked via `javax.lang.model`
+    (`ElementFilter.fieldsIn(...)` over the type + superclass chain, see `DtoMappingReader.hasField(...)`);
+    versus (2) *knowing what the computed getter needs fetched* to execute safely - not solvable at
+    compile time without full static/bytecode analysis of the getter's method body, out of scope.
+  - Resolution: don't attempt to infer (2) automatically. When `DtoMappingReader` detects a `@DtoPath`
+    segment with no backing field, it now fails fast at compile time (`ctx.logError(...)`) unless the
+    developer explicitly declares the real entity paths that must be fetched via
+    `@DtoPath(requires = {...})` (dot-notation, same convention as `@DtoPath`'s own `value()`) - e.g.
+    `@DtoPath(value = "primaryContact.lastName", requires = "contacts")` where `getPrimaryContact()`
+    picks the first entry out of the `contacts` collection. The real prefix before the computed
+    segment (if any) is automatically combined with the declared `requires()` paths, so the developer
+    doesn't need to redundantly repeat it. Declared paths are emitted as bare `.fetch(path)` calls in
+    the generated `FetchGroup` (distinct from the `.fetch(path, "props")` shape used for ordinary
+    scalar `@DtoPath` properties, since there's no specific target property list to narrow to here).
+  - **The zero-extra-fetch case is also supported, via an explicit `requires = {}`** - e.g.
+    `@DtoPath(value = "idBadge", requires = {})` where `getIdBadge()` derives purely from `id`
+    (always fetched regardless). An explicit empty array confirms "nothing extra needed", distinct
+    from omitting `requires()` entirely ("not yet considered", still a compile error) - `requires()`
+    itself can't tell the two cases apart (both read back as an empty `List`), so `DtoMappingReader`
+    checks the avaje-prism-generated `DtoPathPrism.values.requires()` instead, which returns `null`
+    only when the member was left at its default (i.e. omitted from source). `DtoPropertyMeta`
+    correspondingly carries `hasComputedSegment()` as its own boolean flag (set whenever a computed
+    segment was detected at all), independent of whether `requiredFetchPaths()` happens to be empty -
+    an earlier version conflated the two (inferring "has a computed segment" from "has a non-empty
+    requiredFetchPaths list"), which broke exactly this explicit-empty case by falling through to the
+    ordinary scalar `.select(...)` path and failing at runtime with `PersistenceException: Property
+    not found - idBadge` (`idBadge` isn't a real Ebean property, so it can't be selected).
+  - Implemented in `ebean-annotation` (`DtoPath.requires()`), and `querybean-generator`
+    (`DtoMappingReader` computed-segment detection/validation, `DtoPropertyMeta.requiredFetchPaths()`/
+    `hasComputedSegment()`, `DtoMapperWriter.fetchGroupChainCalls()` bare-fetch emission). Test
+    coverage: `tests/test-dto-mapping` `ComputedPathDto`/`TestComputedPath` (happy path, `requires`
+    correctly fetches the dependency and the mapped value is correct), `ComputedPathNoFetchDto`/
+    `TestComputedPathNoFetch` (explicit `requires = {}`, genuinely nothing extra needed), and
+    `querybean-generator`'s `DtoMapperComputedPathTest` (negative case - omitting `requires` on a
+    computed segment is a compile-time `ERROR` diagnostic, verified via direct `javax.tools.JavaCompiler`
+    compilation, mirroring `DtoMapperFetchPathCollisionTest`).
+  - Known gap: the dedup between the computed segment's required fetch paths and existing
+    `pathSelect`/`nestedAssocPaths` keys in `DtoMapperWriter` is a simplified exact-path-string check
+    (skip emitting a duplicate `.fetch(path)`), not full collision detection like the existing
+    NESTED_ONE/MANY vs `@DtoPath` check - a bare `fetch(path)` and an existing `fetch(path,
+    "specific,props")` for the same path string are not merged/reconciled, just left as two separate
+    calls if that edge case arises.
+
+- **Fixed: a single-hop `@DtoPath` rename through a computed/derived getter whose return type is
+  itself a registered nested DTO (`NESTED_ONE`/`NESTED_MANY`, not `SCALAR`) bypassed the
+  computed-segment validation above entirely.** E.g. `@DtoPath("primaryContact")` where the DTO
+  field's declared type is `ContactDto` (a type with its own `@DtoMapping(source = Contact.class,
+  target = ContactDto.class)`) and `getPrimaryContact()` is a computed getter with no backing
+  field on `Customer`. This resolves to a single-segment path, so `DtoMappingReader.resolveProperty()`
+  took its `properties.size() == 1` nested-lookup shortcut and returned early - before the
+  `computedFrom`/`requires()` validation block (added for the `SCALAR` case above) ever ran. The
+  generated `FetchGroup` then emitted a broken `fetch("primaryContact",
+  contactMapper.fetchGroup())` call (`"primaryContact"` isn't a real Ebean fetch path), failing at
+  runtime rather than compile time - the exact class of bug the `SCALAR` fix was meant to close off
+  entirely.
+  - Resolution: restructured `resolveProperty()` so the computed-segment detection/validation block
+    runs *before* the `properties.size() == 1` nested-lookup branch, so both `SCALAR` and
+    `NESTED_ONE`/`NESTED_MANY` paths share the same detection/validation. `DtoPropertyMeta` gained a
+    matching constructor overload for `NESTED_ONE`/`NESTED_MANY` carrying `computedSegment`/
+    `requiredFetchPaths`. In `DtoMapperWriter.fetchGroupChainCalls()`, a `NESTED_ONE`/`NESTED_MANY`
+    property with `hasComputedSegment()` true is routed into `extraFetchPaths` (the same bare
+    `.fetch(path)` mechanism as the `SCALAR` case) instead of emitting `fetch(path,
+    mapper.fetchGroup())` - since the nested mapper's own `FetchGroup` requirements can't be
+    meaningfully attached under a path name that doesn't exist on the source entity.
+  - Note the nested mapper's *own* fetch requirements (e.g. if `ContactDto` itself needed
+    `customer.billingAddress`) are **not** automatically propagated up through a computed segment -
+    only whatever the computed getter itself needs (via `requires()`) is fetched. The nested
+    mapper's `map(...)` call still works via plain Java method invocation regardless (Ebean
+    transparent lazy loading covers any gap), but relying on that silently reintroduces N+1 queries,
+    so the nested DTO used through a computed segment should ideally be a "leaf" shape needing
+    nothing beyond what `requires()` already declares.
+  - Implemented in `querybean-generator` (`DtoMappingReader.resolveProperty()` restructuring,
+    `DtoPropertyMeta`'s new constructor overload, `DtoMapperWriter.fetchGroupChainCalls()`). Test
+    coverage: `tests/test-dto-mapping` `ContactLeafDto`/`ComputedNestedDto`/`TestComputedNestedPath`
+    (happy path - generated `FetchGroup` is `.select("id").fetch("contacts")`, no broken
+    `fetch("primaryContact", ...)` call, and the mapped value is correct end-to-end), and
+    `querybean-generator`'s `DtoMapperComputedPathTest#dtoPathThroughComputedGetter_targetingNestedDto_withoutRequires_expectCompileError`
+    (negative case, mirroring the `SCALAR` one). The `NESTED_MANY` variant (a computed getter
+    returning a `List` of a type with its own registered nested DTO mapping) shares the identical
+    code path but had no dedicated regression test until later confirmed via `Customer
+    .getRecentContacts()` / `ComputedNestedListDto` / `TestComputedNestedListPath` (coverage only,
+    not a bug fix - passed cleanly first try, confirming the shared code path does work end-to-end
+    for both `NESTED_ONE` and `NESTED_MANY`).
+
+- **Fixed: `@DtoRef` never checked for a computed/derived association getter at all.** Unlike
+  `@DtoPath`, `@DtoRef`'s association name (derived by stripping the `Id` suffix off the field
+  name, e.g. `primaryContactId` -> `primaryContact`) was never checked against `hasField(...)` -
+  so `@DtoRef` on a computed getter (e.g. `getPrimaryContact()` picking the first entry out of a
+  `contacts` collection) compiled cleanly and generated a broken `FetchGroup.select("primaryContact")`
+  call (`"primaryContact"` isn't a real Ebean property), failing at runtime rather than compile
+  time - the same class of bug as the original `@DtoPath` fix, just entirely unaddressed for
+  `@DtoRef`'s separate code path.
+  - Resolution: `@DtoRef` gained its own `requires()` attribute (dot-notation, same convention and
+    explicit-empty semantics as `@DtoPath#requires()`, using the same `DtoRefPrism.values.requires()
+    == null` omitted-vs-explicit-empty technique). `DtoMappingReader`'s `@DtoRef` branch now checks
+    `hasField(meta.source(), assocName)` and fails fast at compile time (`ctx.logError(...)`) when
+    the association has no backing field and `requires()` wasn't specified. `DtoPropertyMeta`'s
+    `REF` properties now carry `computedSegment`/`requiredFetchPaths` through the existing fields
+    (no new constructor needed - the full constructor already had the right shape).
+    `DtoMapperWriter.fetchGroupChainCalls()`'s `REF` case now checks `hasComputedSegment()` and
+    routes into `extraFetchPaths` (bare `.fetch(path)`) instead of `rootSelect.add(assoc)` when
+    true - the value expression itself (`source.getPrimaryContact().getId()`, null-guarded) is
+    unaffected, since it's plain Java method invocation regardless of whether the association name
+    is a real Ebean property.
+  - Implemented in `ebean-annotation` (`DtoRef.requires()`), and `querybean-generator`
+    (`DtoMappingReader`'s `@DtoRef` branch, `DtoMapperWriter.fetchGroupChainCalls()`'s `REF` case).
+    Test coverage: `tests/test-dto-mapping` `ComputedRefDto`/`TestComputedRefPath` (happy path -
+    generated `FetchGroup` is `.select("id").fetch("contacts")`, no broken `select("primaryContact")`
+    call, and the mapped id is correct end-to-end), and `querybean-generator`'s
+    `DtoMapperComputedPathTest#dtoRefThroughComputedGetter_withoutRequires_expectCompileError`
+    (negative case, mirroring the `@DtoPath` ones).
+
+- **Fixed: `requires()` path values themselves were never validated against the source type's
+  real property graph.** `@DtoPath(requires = {...})`/`@DtoRef(requires = {...})` values are
+  handed straight through to `FetchGroup.fetch(...)` unmodified - a typo (e.g. `requires =
+  "contactz"` for the real `contacts` property) compiled cleanly, since only the *computed
+  segment itself* was checked against `hasField(...)`, not the developer-declared dependency
+  paths meant to fix it. That silently reintroduced the exact runtime `PersistenceException` the
+  whole `requires()` escape hatch exists to prevent, just one step removed and harder to spot.
+  - Resolution: added `DtoMappingReader.validateRequiresPath(...)`, which walks each dot-notation
+    segment of a declared `requires()` value from the source root (`meta.source()`), checking
+    `hasField(...)` at every hop exactly like `@DtoPath#value()`'s own segments are checked, and
+    unwrapping a `java.util.List`-typed intermediate hop to its element type (via
+    `listElementType(TypeMirror)`) so a collection segment followed by a further hop resolves
+    correctly - needed a new `getterReturnTypeMirror(...)` helper (returning the raw `TypeMirror`
+    rather than converting straight to `TypeElement`, which can't distinguish a `List` from any
+    other declared type) alongside the existing `getterReturnType(...)`. Called for every entry in
+    `pathPrism.requires()`/`refPrism.requires()` right after they're read, for both the `@DtoPath`
+    and `@DtoRef` branches. The already-validated real prefix (segments before the computed one in
+    a `@DtoPath#value()`) is intentionally *not* re-validated, since it was already checked while
+    walking `value()` itself.
+  - Implemented in `querybean-generator` (`DtoMappingReader.validateRequiresPath(...)`,
+    `getterReturnTypeMirror(...)`, called from both the `@DtoPath` and `@DtoRef` branches). Test
+    coverage: `querybean-generator`'s
+    `DtoMapperComputedPathTest#dtoPathRequires_withTypoInPathValue_expectCompileError` (negative
+    case - a typo'd `requires()` segment is a compile-time `ERROR` diagnostic); existing
+    `tests/test-dto-mapping`/`central-access` suites (real multi-segment `requires()` values like
+    `"currentMachine.organisationMachines"`) continue to pass unchanged, confirming the validation
+    doesn't false-positive on legitimate paths.
+
+- **Fixed: a bare, full `requires()` fetch and a sibling property's narrowed `@DtoPath` fetch of
+  the exact same path silently conflicted, with the narrow one always (incorrectly) winning.**
+  `DtoMapperWriter.fetchGroupChainCalls()`'s dedup logic used to skip emitting a computed
+  segment's bare `fetch(path)` call whenever another property's `@DtoPath` already had a narrowed
+  `fetch(path, "specific,props")` entry for that exact path string - on the assumption the two
+  were interchangeable/redundant. They aren't: `FetchGroup`'s builder (`OrmQueryDetail.fetch(...)`)
+  keys fetch calls by path in a plain `Map` and **replaces** rather than merges same-path entries,
+  so whichever call format was emitted meant the *other* was silently discarded. Since the narrow
+  entry was always emitted first and the bare one skipped whenever it existed, the narrow selection
+  always won - meaning a computed getter's `requires()` declaration could be completely ignored
+  whenever an unrelated sibling `@DtoPath` happened to narrow-select the exact same path, leaving
+  whatever extra properties the computed getter actually touches unfetched (a silent lazy load, or
+  a hard `LazyInitialisationException` outside a persistence context).
+  - Resolution: reversed the priority - `fetchGroupChainCalls()` now skips a narrowed `pathSelect`
+    entry when `extraFetchPaths` (the computed segment's `requires()`) declares the exact same
+    path, letting the bare, full `fetch(path)` call win instead. This is always safe since a full
+    fetch is a superset of any narrower property selection - the narrow entry's own properties are
+    included within it regardless. The existing `nestedAssocPaths` priority (a `NESTED_ONE`/
+    `NESTED_MANY` property's full `fetch(path, mapper.fetchGroup())` always wins over a bare
+    `fetch(path)`) was correct already and left unchanged - a nested mapper's own `FetchGroup` is
+    strictly richer than either form and must not be replaced by either.
+  - Implemented in `querybean-generator` (`DtoMapperWriter.fetchGroupChainCalls()`). Test coverage:
+    `tests/test-dto-mapping` `FetchCollisionDto`/`TestFetchCollisionPath`, plus a new computed
+    getter `Customer.getBillingSummary()` (reads `billingAddress.getLine1()`, deliberately a
+    different `Address` property to the `city` narrowly selected by a sibling `@DtoPath` on the
+    same DTO) - confirmed to reproduce `LazyInitialisationException: Property not loaded: line1`
+    when the fix is reverted, and pass cleanly (correct `line1`-derived value, generated
+    `FetchGroup` is `.select("id").fetch("billingAddress")` with no narrowed variant at all) with
+    it in place.
+
+- **Fixed: two `@DtoMixin` companion types targeting the same DTO class silently conflicted, with
+  the second-processed one winning.** `DtoMappingReader.collectMixins()` keyed a single
+  `mixinsByTarget` map by the target DTO's FQN, and `Map.put(...)` unconditionally overwrote any
+  existing entry - so if two mixin interfaces (e.g. a legitimate one plus an accidental duplicate,
+  or two independently-added mixins that both happened to target the same generated/unowned DTO)
+  both declared `@DtoMixin(SameDto.class)`, whichever was visited last by
+  `roundEnv.getElementsAnnotatedWith(...)` silently won, and *all* of the other mixin's
+  `@DtoPath`/`@DtoRef`/`@DtoConvert` overlays were discarded with no diagnostic at all.
+  - Resolution: `collectMixins()` now checks for an existing registration before storing a new one
+    and raises a compile `ERROR` naming both the target and the already-registered mixin's
+    qualified name, rather than silently overwriting it.
+  - Implemented in `querybean-generator` (`DtoMappingReader.collectMixins()`). Test coverage: new
+    negative compile-error test `DtoMapperComputedPathTest#duplicateDtoMixin_forSameTarget_expectCompileError`
+    (two minimal `@DtoMixin(FooDto.class)` interfaces both declaring a `bar()` method, compiled
+    together, asserting the `Duplicate @DtoMixin` diagnostic is raised); existing
+    `tests/test-dto-mapping` `TestDtoMixin` (single, legitimate mixin usage) continues to pass
+    unchanged.
+
+- **Fixed: `@DtoRef` and `@DtoPath` both present on the same field silently conflicted, with
+  `@DtoRef` always (invisibly) winning.** `resolveProperty()` checked `refPrism != null` first and
+  returned immediately whenever present, so a field carrying both annotations at once - whether by
+  copy/paste mistake, a half-finished rename from one style to the other, or simple confusion
+  between the two escape hatches - had its `@DtoPath` completely ignored with no diagnostic at all.
+  - Resolution: `resolveProperty()` now resolves both prisms upfront and raises a compile `ERROR`
+    naming the field when both are present, rather than silently picking `@DtoRef` and discarding
+    `@DtoPath`.
+  - Implemented in `querybean-generator` (`DtoMappingReader.resolveProperty()`). Test coverage: new
+    negative compile-error test `DtoMapperComputedPathTest#dtoRefAndDtoPath_onSameField_expectCompileError`
+    (a field carrying both `@DtoRef` and `@DtoPath("bar.id")` over a real, non-computed association,
+    isolating the conflict diagnostic from the separate computed-getter `requires()` diagnostics).
+
+- **Fixed: `@DtoConvert` on a `NESTED_ONE`/`NESTED_MANY` property was silently ignored.**
+  `resolveProperty()` resolves the property's `DtoConverterMeta` unconditionally up front (before
+  it's known whether the property will resolve to `SCALAR`/`REF`/`NESTED_ONE`/`NESTED_MANY`), but
+  only the `SCALAR`/`REF` `DtoPropertyMeta` constructors actually accept/store a converter - the
+  `NESTED_ONE`/`NESTED_MANY` constructor calls never took one, so a resolved converter was simply
+  dropped on the floor with no diagnostic. A developer adding `@DtoConvert` to a nested-DTO field
+  (e.g. hoping to post-process the nested mapper's result) would see it silently do nothing -
+  `DtoMapperWriter.propertyValueExpression()`'s `NESTED_ONE`/`NESTED_MANY` cases call straight into
+  `mapperFieldName(property) + ".map(...)"`/`".mapList(...)"` with no converter wrapping at all.
+  - Resolution: added `rejectConverterOnNested(...)`, called at each of the four call sites that
+    construct a `NESTED_ONE`/`NESTED_MANY` `DtoPropertyMeta` (the single-hop `@DtoPath`-rename
+    branch's two cases, and the plain non-`@DtoPath` branch's two cases) - raises a compile `ERROR`
+    naming the field whenever a converter was resolved for it, rather than silently discarding it.
+  - Implemented in `querybean-generator` (`DtoMappingReader.resolveProperty()`,
+    `rejectConverterOnNested()`). Test coverage: new negative compile-error test
+    `DtoMapperComputedPathTest#dtoConvertOnNestedOne_expectCompileError` (a `NESTED_ONE` field
+    carrying `@DtoConvert` over a legitimately nested, separately-`@DtoMapping`-registered type);
+    existing `tests/test-dto-mapping` suite (no nested property currently combines `@DtoConvert`
+    with `NESTED_ONE`/`NESTED_MANY`) continues to pass unchanged, confirming no false positives on
+    plain nested properties.
+
+- **Fixed: `@DtoConvert(method = ...)` resolution ignored parameter arity/overloads.** The shared
+  `findMethod(type, name)` helper (also used for the builder's `build()` lookup and `@DtoMixin`
+  companion-method lookup) matches purely by simple name - the first `ExecutableElement` found -
+  with no arity or parameter-type check at all. For `@DtoConvert` specifically this is a real risk:
+  its documented contract is a method "taking the source property value and returning the
+  converted DTO property value" (i.e. exactly one parameter), but a shared/reusable conversion
+  utility class is a very plausible place to have multiple same-named overloads (e.g. `format
+  (Instant)` and `format(LocalDate)`) - `findMethod` would silently bind to whichever one
+  `ElementFilter.methodsIn` happened to return first, independent of which one the developer
+  actually meant, generating either a confusing arity/type-mismatch compile error in the generated
+  mapper or, if both overloads happened to be call-compatible, silently invoking the wrong one.
+  - Resolution: added a dedicated `findConverterMethod(...)` (used only by `resolveConverter()`,
+    leaving the shared `findMethod()` untouched for the builder/mixin call sites which have their
+    own, different arity expectations) that filters same-named candidates down to those taking
+    exactly one parameter. Zero matches raises a clear "not found ... taking exactly one
+    parameter" error; more than one match (multiple 1-arg overloads sharing the name) raises an
+    "ambiguous - N overloads take exactly one parameter" error, since `@DtoConvert` has no
+    parameter-type-based way to disambiguate and the developer must rename one of the overloads.
+  - Implemented in `querybean-generator` (`DtoMappingReader.resolveConverter()`,
+    `findConverterMethod()`). Test coverage: new negative compile-error tests
+    `DtoMapperComputedPathTest#dtoConvertMethod_withAmbiguousOverloads_expectCompileError` (two
+    same-named 1-arg overloads) and `#dtoConvertMethod_withWrongArity_expectCompileError` (a
+    same-named 0-arg method, no 1-arg candidate at all); existing `tests/test-dto-mapping`
+    converter usage (a single, unambiguous 1-arg method per converter type) continues to resolve
+    and pass unchanged.
 
 ## References
 

ebean-api/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean api</name>

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

@@ -0,0 +1,137 @@
+package io.ebean;
+
+/**
+ * Runtime helpers used by generated {@link DtoMapper} implementations to safely resolve a
+ * primitive-typed DTO field whose value is derived from a multi-hop {@code @DtoPath} that
+ * traverses a nullable intermediate relation.
+ * <p>
+ * A {@code null}-guarded getter-chain (e.g. {@code source.getOrganisation() == null ? null :
+ * source.getOrganisation().getId()}) always types as the boxed wrapper (since one branch is the
+ * {@code null} literal). When the DTO's target field is a primitive (e.g. {@code long
+ * organisationId}), passing that boxed expression to the constructor auto-unboxes it - which
+ * throws a raw, unhelpful {@link NullPointerException} if the relation really is {@code null}.
+ * <p>
+ * These methods give the generated mapper a choice, controlled by {@code @DtoPath#failOnNull()}:
+ * default to the primitive's zero-equivalent value ({@code orZero} methods, the default), or
+ * throw a clear, descriptive exception naming the offending property path ({@code require}
+ * methods, opted into via {@code failOnNull = true}).
+ *
+ * @see io.ebean.annotation.DtoPath
+ */
+public final class DtoMapperSupport {
+
+  private DtoMapperSupport() {
+  }
+
+  /** Return {@code 0} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static long orZero(Long value) {
+    return value == null ? 0L : value;
+  }
+
+  /** Return {@code 0} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static int orZero(Integer value) {
+    return value == null ? 0 : value;
+  }
+
+  /** Return {@code 0} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static short orZero(Short value) {
+    return value == null ? 0 : value;
+  }
+
+  /** Return {@code 0} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static byte orZero(Byte value) {
+    return value == null ? 0 : value;
+  }
+
+  /** Return {@code 0.0} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static double orZero(Double value) {
+    return value == null ? 0.0 : value;
+  }
+
+  /** Return {@code 0.0f} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static float orZero(Float value) {
+    return value == null ? 0.0f : value;
+  }
+
+  /** Return {@code false} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static boolean orZero(Boolean value) {
+    return value != null && value;
+  }
+
+  /** Return {@code '\u0000'} if {@code value} is {@code null}, otherwise its unboxed value. */
+  public static char orZero(Character value) {
+    return value == null ? '\u0000' : value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static long require(Long value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static int require(Integer value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static short require(Short value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static byte require(Byte value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static double require(Double value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static float require(Float value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static boolean require(Boolean value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  /** Return the unboxed value, or throw if {@code value} is {@code null}. */
+  public static char require(Character value, String path) {
+    if (value == null) {
+      throw failure(path);
+    }
+    return value;
+  }
+
+  private static IllegalStateException failure(String path) {
+    return new IllegalStateException(
+      "@DtoPath(\"" + path + "\") resolved to null via a nullable intermediate relation, but the"
+        + " target DTO field is primitive and failOnNull=true - either handle the null case in"
+        + " source data, use a boxed wrapper type for the DTO field, or remove failOnNull to"
+        + " default to the primitive's zero-equivalent value instead.");
+  }
+}

ebean-bench/pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-bench</artifactId>

ebean-bom/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean bom</name>
@@ -89,25 +89,25 @@
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-api</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-core</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-core-type</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
@@ -125,13 +125,13 @@
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-jackson-mapper</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-ddl-generator</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
@@ -155,37 +155,37 @@
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-querybean</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>querybean-generator</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>kotlin-querybean-generator</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-test</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-redis</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-spring-txn</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <!-- platforms -->
@@ -193,91 +193,91 @@
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-clickhouse</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-db2</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-h2</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-hana</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-mariadb</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-mysql</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-nuodb</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-oracle</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-postgres</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-postgis</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-postgis-types</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-pgvector</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-pgvector-types</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-sqlite</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
       <dependency>
         <groupId>io.ebean</groupId>
         <artifactId>ebean-sqlserver</artifactId>
-        <version>18.2.0</version>
+        <version>18.3.0</version>
       </dependency>
 
     </dependencies>

ebean-core-json/pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <groupId>io.ebean</groupId>
     <artifactId>ebean-parent</artifactId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
   <artifactId>ebean-core-json</artifactId>
   <name>ebean-core-json</name>
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

ebean-core-type/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-core-type</artifactId>
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

ebean-core/pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-core</artifactId>
@@ -22,13 +22,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core-json</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -52,7 +52,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core-type</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -157,21 +157,21 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlserver</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-core/src/main/java/io/ebeaninternal/server/persist/dml/InsertMetaOptionsPostgres.java

@@ -18,12 +18,14 @@ final class InsertMetaOptionsPostgres implements InsertMetaOptions {
   private final InsertMeta meta;
   private final BeanDescriptor<?> desc;
   private final String baseTable;
+  private final List<String> nonUpdatableColumns;
   private final Map<String, String> sqlCache = new ConcurrentHashMap<>();
 
   InsertMetaOptionsPostgres(InsertMeta meta, BeanDescriptor<?> desc) {
     this.meta = meta;
     this.desc = desc;
     this.baseTable = desc.baseTable();
+    this.nonUpdatableColumns = InsertMetaOptionsSupport.nonUpdatableColumns(desc);
   }
 
   @Override
@@ -84,6 +86,7 @@ final class InsertMetaOptionsPostgres implements InsertMetaOptions {
   private void setColumns(boolean withId, GenerateDmlRequest request, List<String> uniqueColumns) {
     List<String> columns = request.columns();
     columns.removeAll(uniqueColumns);
+    columns.removeAll(nonUpdatableColumns);
     if (withId) {
       BeanProperty idProperty = desc.idProperty();
       if (idProperty != null && !idProperty.isEmbedded()) {

ebean-core/src/main/java/io/ebeaninternal/server/persist/dml/InsertMetaOptionsSqlite.java

@@ -21,12 +21,14 @@ final class InsertMetaOptionsSqlite implements InsertMetaOptions {
   private final InsertMeta meta;
   private final BeanDescriptor<?> desc;
   private final String baseTable;
+  private final List<String> nonUpdatableColumns;
   private final Map<String, String> sqlCache = new ConcurrentHashMap<>();
 
   InsertMetaOptionsSqlite(InsertMeta meta, BeanDescriptor<?> desc) {
     this.meta = meta;
     this.desc = desc;
     this.baseTable = desc.baseTable();
+    this.nonUpdatableColumns = InsertMetaOptionsSupport.nonUpdatableColumns(desc);
   }
 
   @Override
@@ -85,6 +87,7 @@ final class InsertMetaOptionsSqlite implements InsertMetaOptions {
   private void setColumns(boolean withId, GenerateDmlRequest request, List<String> uniqueColumns) {
     List<String> columns = request.columns();
     columns.removeAll(uniqueColumns);
+    columns.removeAll(nonUpdatableColumns);
     if (withId) {
       BeanProperty idProperty = desc.idProperty();
       if (idProperty != null && !idProperty.isEmbedded()) {

ebean-core/src/main/java/io/ebeaninternal/server/persist/dml/InsertMetaOptionsSupport.java

@@ -0,0 +1,37 @@
+package io.ebeaninternal.server.persist.dml;
+
+import io.ebeaninternal.server.deploy.BeanDescriptor;
+import io.ebeaninternal.server.deploy.BeanProperty;
+import io.ebeaninternal.server.deploy.generatedproperty.GeneratedProperty;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Shared support for the platform specific insert on conflict do update generation.
+ */
+final class InsertMetaOptionsSupport {
+
+  private InsertMetaOptionsSupport() {
+  }
+
+  /**
+   * Return the columns that should be excluded from the generated "do update set" clause
+   * as they are not updatable, e.g. {@code @Column(updatable=false)} or a generated property
+   * that is insert only such as {@code @WhenCreated}/{@code @WhoCreated}.
+   */
+  static List<String> nonUpdatableColumns(BeanDescriptor<?> desc) {
+    List<String> columns = new ArrayList<>();
+    for (BeanProperty prop : desc.propertiesNonTransient()) {
+      if (!prop.isDbUpdatable() || isInsertOnlyGenerated(prop)) {
+        columns.add(prop.dbColumn());
+      }
+    }
+    return columns;
+  }
+
+  private static boolean isInsertOnlyGenerated(BeanProperty prop) {
+    GeneratedProperty gen = prop.generatedProperty();
+    return gen != null && gen.includeInInsert() && !gen.includeInUpdate();
+  }
+}

ebean-ddl-generator/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean ddl generation</name>
@@ -28,14 +28,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core-type</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -65,7 +65,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-all</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-jackson-mapper/pom.xml

@@ -3,7 +3,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 
@@ -15,7 +15,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core-type</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 

ebean-net-postgis-types/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean net postgis types</name>
@@ -19,14 +19,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <!-- provided scope -->
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -54,7 +54,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-opentelemetry/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-opentelemetry</artifactId>
@@ -28,7 +28,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -71,21 +71,21 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>querybean-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 

ebean-pgvector-types/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean pgvector types</name>
@@ -19,14 +19,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <!-- provided scope -->
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -54,7 +54,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-postgis-types/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean postgis types</name>
@@ -19,14 +19,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <!-- provided scope -->
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -62,7 +62,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-querybean/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean querybean</name>
@@ -17,7 +17,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -59,14 +59,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-ddl-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
@@ -80,7 +80,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>querybean-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 

ebean-redis/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-redis</artifactId>
@@ -29,35 +29,35 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>querybean-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 

ebean-redisson/pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-redisson</artifactId>
@@ -29,35 +29,35 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>querybean-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 

ebean-spring-txn/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>ebean-spring-txn</artifactId>
@@ -28,7 +28,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
@@ -77,7 +77,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-test/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>ebean test</name>
@@ -33,20 +33,20 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>provided</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-ddl-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -149,14 +149,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-jackson-mapper</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-all</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

ebean-test/src/test/java/org/tests/insert/EConflictWithCreated.java

@@ -0,0 +1,61 @@
+package org.tests.insert;
+
+import io.ebean.annotation.Index;
+import io.ebean.annotation.WhenCreated;
+import io.ebean.annotation.WhenModified;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import java.time.Instant;
+
+/**
+ * Used to verify that insert on conflict do update excludes insert-only generated
+ * properties (such as {@code @WhenCreated}) from the generated update set clause.
+ */
+@Entity
+public class EConflictWithCreated {
+
+  @Id
+  Long id;
+
+  @Index(unique = true)
+  String code;
+
+  @WhenCreated
+  Instant whenCreated;
+
+  @WhenModified
+  Instant whenUpdated;
+
+  public Long getId() {
+    return id;
+  }
+
+  public void setId(Long id) {
+    this.id = id;
+  }
+
+  public String getCode() {
+    return code;
+  }
+
+  public void setCode(String code) {
+    this.code = code;
+  }
+
+  public Instant getWhenCreated() {
+    return whenCreated;
+  }
+
+  public void setWhenCreated(Instant whenCreated) {
+    this.whenCreated = whenCreated;
+  }
+
+  public Instant getWhenUpdated() {
+    return whenUpdated;
+  }
+
+  public void setWhenUpdated(Instant whenUpdated) {
+    this.whenUpdated = whenUpdated;
+  }
+}

ebean-test/src/test/java/org/tests/insert/TestInsertOnConflict.java

@@ -307,6 +307,35 @@ class TestInsertOnConflict extends BaseTestCase {
     assertThat(list.get(0).getWhenUpdated()).isEqualTo(bean.getWhenUpdated());
   }
 
+  @ForPlatform({Platform.POSTGRES, Platform.YUGABYTE, Platform.SQLITE})
+  @Test
+  void insertOnConflictUpdate_excludesWhenCreatedFromUpdateSet() {
+    Database db = DB.getDefault();
+    db.truncate(EConflictWithCreated.class);
+    LoggedSql.start();
+
+    var bean = new EConflictWithCreated();
+    bean.setCode("abc");
+    db.insert(bean, ON_CONFLICT_UPDATE);
+
+    var bean2 = new EConflictWithCreated();
+    bean2.setCode("abc");
+    db.insert(bean2, ON_CONFLICT_UPDATE);
+
+    var sql = LoggedSql.stop();
+    assertThat(sql).hasSize(2);
+    // when_created is not included in the "do update set" clause - it is insert only
+    assertThat(sql.get(0)).contains("on conflict (code) do update set when_updated=excluded.when_updated");
+    assertThat(sql.get(0)).doesNotContain("when_created=excluded.when_created");
+    assertThat(sql.get(1)).contains("on conflict (code) do update set when_updated=excluded.when_updated");
+    assertThat(sql.get(1)).doesNotContain("when_created=excluded.when_created");
+
+    List<EConflictWithCreated> list = db.find(EConflictWithCreated.class).findList();
+    assertThat(list).hasSize(1);
+    // original whenCreated value is preserved rather than being overwritten by the 2nd insert
+    assertThat(list.get(0).getWhenCreated()).isEqualTo(bean.getWhenCreated());
+  }
+
   @ForPlatform({Platform.POSTGRES, Platform.YUGABYTE})
   @Test
   void updateQueryReturning() throws SQLException {

kotlin-querybean-generator/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>kotlin querybean generator</name>
@@ -21,7 +21,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-querybean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
@@ -35,7 +35,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-core</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
@@ -56,14 +56,14 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-ddl-generator</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
 

platforms/all/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,67 +16,67 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-clickhouse</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-db2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-hana</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-hsqldb</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-mysql</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-mariadb</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-nuodb</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-oracle</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-postgres</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlanywhere</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlite</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-sqlserver</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/clickhouse/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/db2/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/h2/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <!-- Provided scope so that the H2HistoryTrigger can live in Ebean core

platforms/hana/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/hsqldb/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-h2</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/mariadb/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,13 +16,13 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-platform-mysql</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/mysql/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/nuodb/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/oracle/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>platforms</artifactId>

platforms/postgres/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>

platforms/sqlanywhere/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/sqlite/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

platforms/sqlserver/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
     <relativePath>../..</relativePath>
   </parent>
 
@@ -16,7 +16,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
   </dependencies>

pom.xml

@@ -9,7 +9,7 @@
 
   <groupId>io.ebean</groupId>
   <artifactId>ebean-parent</artifactId>
-  <version>18.2.0</version>
+  <version>18.3.0</version>
   <packaging>pom</packaging>
 
   <name>ebean parent</name>
@@ -45,7 +45,7 @@
     <ebean-persistence-api.version>3.2</ebean-persistence-api.version>
     <ebean-types.version>3.0</ebean-types.version>
 
-    <ebean-annotation.version>8.6</ebean-annotation.version>
+    <ebean-annotation.version>8.9</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>

querybean-generator/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <name>querybean generator</name>
@@ -45,7 +45,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-api</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>
   </dependencies>

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

@@ -104,6 +104,9 @@ class DtoMapperWriter {
     if (!meta.converterDeps().isEmpty()) {
       imports.add("io.ebean.DtoConverterManager");
     }
+    if (meta.properties().stream().anyMatch(DtoPropertyMeta::usesMapperSupport)) {
+      imports.add("io.ebean.DtoMapperSupport");
+    }
     if (variableProperties().stream().anyMatch(p -> p.kind() == DtoPropertyMeta.Kind.NESTED_MANY)) {
       imports.add("java.util.List");
     }
@@ -222,21 +225,41 @@ class DtoMapperWriter {
     }
     Set<String> nestedAssocPaths = new LinkedHashSet<>();
     for (DtoPropertyMeta property : activeProperties) {
-      if (property.kind() == DtoPropertyMeta.Kind.NESTED_ONE || property.kind() == DtoPropertyMeta.Kind.NESTED_MANY) {
+      if ((property.kind() == DtoPropertyMeta.Kind.NESTED_ONE || property.kind() == DtoPropertyMeta.Kind.NESTED_MANY)
+        && !property.hasComputedSegment()) {
         nestedAssocPaths.add(property.sourcePropertyPath().get(0));
       }
     }
     Set<String> rootSelect = new LinkedHashSet<>();
     Map<String, List<String>> pathSelect = new LinkedHashMap<>();
+    Set<String> extraFetchPaths = new LinkedHashSet<>();
     List<String> fetchCalls = new ArrayList<>();
     for (DtoPropertyMeta property : activeProperties) {
       switch (property.kind()) {
         case NESTED_ONE:
         case NESTED_MANY:
+          if (property.hasComputedSegment()) {
+            // a single-hop @DtoPath rename traversing a computed/derived getter (no backing
+            // field) that happens to target a nested DTO type - just as unfetchable via
+            // fetch(path, mapper.fetchGroup()) as the analogous SCALAR case, since "path" here
+            // isn't a real Ebean fetch path either. The nested mapper is still invoked directly
+            // against whatever the getter returns (see DtoMapperWriter#propertyValueExpression) -
+            // it's purely the FetchGroup derivation that must fall back to @DtoPath#requires().
+            extraFetchPaths.addAll(property.requiredFetchPaths());
+            break;
+          }
           fetchCalls.add(String.format("fetch(\"%s\", %s.fetchGroup())",
             property.sourcePropertyPath().get(0), mapperFieldName(property)));
           break;
         case SCALAR:
+          if (property.hasComputedSegment()) {
+            // the path traverses a computed/derived getter (no backing field) - its own segments
+            // past that point aren't real Ebean fetch paths, so don't add them to pathSelect/
+            // rootSelect at all; @DtoPath#requires() (plus the real prefix, if any) already names
+            // exactly what needs fetching instead - see DtoPropertyMeta#requiredFetchPaths().
+            extraFetchPaths.addAll(property.requiredFetchPaths());
+            break;
+          }
           List<String> path = property.sourcePropertyPath();
           if (path.size() == 1) {
             rootSelect.add(path.get(0));
@@ -254,6 +277,15 @@ class DtoMapperWriter {
           break;
         case REF:
         default:
+          if (property.hasComputedSegment()) {
+            // the association has no backing field (a computed/derived getter) - "assoc" isn't a
+            // real Ebean property name, so it can't be handed to FetchGroup.select(...) directly;
+            // @DtoRef#requires() already names exactly what needs fetching instead - see
+            // DtoPropertyMeta#requiredFetchPaths(). The value mapping itself (source.getAssoc().
+            // getId()) still works via plain Java method invocation regardless.
+            extraFetchPaths.addAll(property.requiredFetchPaths());
+            break;
+          }
           String assoc = property.sourcePropertyPath().get(0);
           if (!nestedAssocPaths.contains(assoc)) {
             rootSelect.add(assoc);
@@ -262,8 +294,27 @@ class DtoMapperWriter {
       }
     }
     for (var entry : pathSelect.entrySet()) {
+      if (extraFetchPaths.contains(entry.getKey())) {
+        // an unrelated computed-segment property also needs a bare, full fetch(path) at this
+        // exact same path (emitted below) - FetchGroup's builder REPLACES (not merges) same-path
+        // fetch calls (OrmQueryDetail.fetch(...) is a plain Map.put keyed by path), so emitting
+        // both a narrowed fetch(path, "props") here and a bare fetch(path) below would leave
+        // only whichever call happens to be added last in effect, silently discarding the other's
+        // requirement depending on emission order. Skip the narrow entry - a full fetch(path) is
+        // always a safe superset of any narrower property selection, so let the bare fetch below
+        // win deterministically instead of depending on iteration order.
+        continue;
+      }
       fetchCalls.add(String.format("fetch(\"%s\", \"%s\")", entry.getKey(), String.join(",", entry.getValue())));
     }
+    for (String extraPath : extraFetchPaths) {
+      // already covered by another property's NESTED_ONE/MANY fetch of the exact same path (a
+      // full nested mapper.fetchGroup()) - that's richer than a bare fetch(path) (which would
+      // replace it and lose the nested mapper's own fetch requirements), so it must win instead.
+      if (!nestedAssocPaths.contains(extraPath)) {
+        fetchCalls.add(String.format("fetch(\"%s\")", extraPath));
+      }
+    }
     List<String> calls = new ArrayList<>();
     if (!rootSelect.isEmpty()) {
       calls.add(String.format("select(\"%s\")", String.join(",", rootSelect)));

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

@@ -135,7 +135,14 @@ class DtoMappingReader {
         ctx.logError(element, "@DtoMixin value() must be a class type");
         continue;
       }
-      mixinsByTarget.put(target.getQualifiedName().toString(), (TypeElement) element);
+      String targetFqn = target.getQualifiedName().toString();
+      TypeElement existing = mixinsByTarget.get(targetFqn);
+      if (existing != null) {
+        ctx.logError(element, "Duplicate @DtoMixin for target %s - %s already declares a mixin for"
+          + " it, only one @DtoMixin is allowed per target", targetFqn, existing.getQualifiedName());
+        continue;
+      }
+      mixinsByTarget.put(targetFqn, (TypeElement) element);
     }
   }
 
@@ -444,63 +451,178 @@ class DtoMappingReader {
     String name = field.getSimpleName().toString();
     DtoConverterMeta converter = resolveConverter(field, meta);
     DtoRefPrism refPrism = prismOn(field, meta, DtoRefPrism::getInstanceOn);
+    DtoPathPrism pathPrism = prismOn(field, meta, DtoPathPrism::getInstanceOn);
+    if (refPrism != null && pathPrism != null) {
+      ctx.logError(field, "%s.%s carries both @DtoRef and @DtoPath - these are mutually exclusive"
+        + " (@DtoRef always wins silently otherwise), remove whichever doesn't apply",
+        meta.targetFullName(), name);
+    }
     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);
+      boolean computedSegment = meta.source() == null || !hasField(meta.source(), assocName);
+      List<String> requiredFetchPaths = List.of();
+      if (computedSegment) {
+        // the association has no backing field on the source - a computed/derived getter (e.g.
+        // picking one entry out of a collection) rather than a real, fetchable Ebean relation, so
+        // its data dependencies can't be inferred automatically - same problem class, and same
+        // requires() escape hatch, as the analogous @DtoPath handling above. Unlike @DtoPath there's
+        // no "real prefix" to combine with, since @DtoRef only ever derives a single association
+        // name directly off the source (no dotted value() of its own).
+        if (refPrism.values.requires() == null) {
+          ctx.logError(field,
+            "@DtoRef on %s traverses '%s' which has no backing field on %s - it looks like a"
+              + " computed/derived getter rather than a real, fetchable Ebean relation, so its data"
+              + " dependencies can't be inferred automatically. Specify @DtoRef(requires = {...})"
+              + " naming the real entity paths that must be fetched for it to execute safely, or"
+              + " requires = {} if it genuinely needs nothing extra fetched, or remove @DtoRef and"
+              + " compute this value another way (e.g. @DtoConvert).",
+            meta.targetFullName(), assocName, meta.source() != null ? meta.source().getSimpleName() : "?");
+        }
+        requiredFetchPaths = refPrism.requires();
+        String annotationDisplay = String.format("@DtoRef(requires = ...) on %s.%s", meta.targetFullName(), name);
+        for (String requiresPath : requiredFetchPaths) {
+          validateRequiresPath(field, meta.source(), requiresPath, annotationDisplay);
+        }
+      }
+      // @DtoRef has no failOnNull escape hatch - always default to the primitive's zero-equivalent
+      // rather than let a null-guarded getter chain auto-unbox to a NullPointerException.
+      return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.REF, List.of(assocGetter, idGetter), List.of(assocName, "id"),
+        null, converter, field.asType().getKind().isPrimitive(), false, computedSegment, requiredFetchPaths);
     }
-    DtoPathPrism pathPrism = prismOn(field, meta, DtoPathPrism::getInstanceOn);
     if (pathPrism != null) {
       List<String> getters = new ArrayList<>();
       List<String> properties = new ArrayList<>();
       TypeElement currentType = meta.source();
+      TypeElement computedDeclaringType = null;
+      int computedFrom = -1;
       for (String segment : pathPrism.value().split("\\.")) {
         String getter = getterName(currentType, segment);
         getters.add(getter);
         properties.add(segment);
+        if (computedFrom < 0 && (currentType == null || !hasField(currentType, segment))) {
+          computedFrom = properties.size() - 1;
+          computedDeclaringType = currentType;
+        }
         currentType = currentType != null ? getterReturnType(currentType, getter) : null;
       }
+      List<String> requiredFetchPaths = List.of();
+      if (computedFrom >= 0) {
+        // a segment with no backing field is a computed/derived getter, not a real, fetchable
+        // Ebean property - its own data dependencies (what it touches internally) can't be
+        // inferred from the path alone, so require the developer to spell them out explicitly
+        // via @DtoPath(requires = {...}) rather than silently generating a FetchGroup.fetch(...)
+        // call for a path segment Ebean doesn't actually recognise (which only fails at runtime).
+        // Computed here regardless of whether the path ultimately resolves to a plain SCALAR or a
+        // single-hop NESTED_ONE/MANY rename below - both cases share the exact same problem: a
+        // fake path segment that can't be handed to FetchGroup as a real fetch/select target.
+        String realPrefix = computedFrom == 0 ? null : String.join(".", properties.subList(0, computedFrom));
+        // pathPrism.requires() always returns List.of() whether the attribute was explicitly
+        // written as an empty array or omitted entirely - only pathPrism.values.requires() (which
+        // returns null for a defaulted/omitted member) can tell the two apart. That distinction
+        // matters here: an explicit requires = {} is the developer's way of confirming the
+        // computed getter genuinely needs nothing extra fetched, whereas omitting requires
+        // entirely means they haven't considered it yet - only the latter should fail the build.
+        if (pathPrism.values.requires() == null) {
+          String hint = realPrefix != null
+            ? String.format(" (e.g. requires = \"%s\", or a deeper path under it your getter actually needs)", realPrefix)
+            : "";
+          ctx.logError(field,
+            "@DtoPath(\"%s\") on %s traverses '%s' which has no backing field on %s - it looks like"
+              + " a computed/derived getter rather than a real, fetchable Ebean property, so its data"
+              + " dependencies can't be inferred automatically. Specify @DtoPath(requires = {...})"
+              + " naming the real entity paths that must be fetched for it to execute safely%s, or"
+              + " requires = {} if it genuinely needs nothing extra fetched, or remove @DtoPath and"
+              + " compute this value another way (e.g. @DtoConvert).",
+            pathPrism.value(), meta.targetFullName(), properties.get(computedFrom),
+            computedDeclaringType != null ? computedDeclaringType.getSimpleName() : "?", hint);
+        }
+        List<String> combined = new ArrayList<>();
+        if (realPrefix != null) {
+          combined.add(realPrefix);
+        }
+        combined.addAll(pathPrism.requires());
+        requiredFetchPaths = combined;
+        // realPrefix is already known-good (each of its segments was hasField-checked while
+        // walking value() above) - only the developer-declared requires() values themselves are
+        // unchecked and need validating here.
+        String annotationDisplay = String.format("@DtoPath(\"%s\").requires()", pathPrism.value());
+        for (String requiresPath : pathPrism.requires()) {
+          validateRequiresPath(field, meta.source(), requiresPath, annotationDisplay);
+        }
+      }
       // 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.
+      // derivation for NESTED_ONE/MANY only supports a single association name. A computed
+      // segment here (the single segment has no backing field - e.g. @DtoPath("primaryContact")
+      // where getPrimaryContact() is a derived getter) is just as unfetchable as the SCALAR case
+      // above, so it carries the same computedFrom/requiredFetchPaths validation through - see
+      // DtoMapperWriter's NESTED_ONE/NESTED_MANY handling of DtoPropertyMeta#hasComputedSegment().
       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);
+            rejectConverterOnNested(field, converter, name, meta);
+            return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_MANY, getters, properties, nested,
+              computedFrom >= 0, requiredFetchPaths);
           }
         } else {
           DtoBeanMeta nested = lookupByTarget(fieldType);
           if (nested != null) {
-            return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_ONE, getters, properties, nested);
+            rejectConverterOnNested(field, converter, name, meta);
+            return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.NESTED_ONE, getters, properties, nested,
+              computedFrom >= 0, requiredFetchPaths);
           }
         }
       }
-      return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.SCALAR, getters, properties, null, converter);
+      // A multi-hop path can pass through a nullable intermediate relation - if the DTO field is
+      // primitive, the generated null-guarded getter chain would otherwise auto-unbox a null
+      // straight into a NullPointerException. Default to the primitive's zero-equivalent value,
+      // or fail fast with a clear message instead when @DtoPath(failOnNull = true).
+      return new DtoPropertyMeta(name, DtoPropertyMeta.Kind.SCALAR, getters, properties, null, converter,
+        field.asType().getKind().isPrimitive(), pathPrism.failOnNull(), computedFrom >= 0, requiredFetchPaths);
     }
     TypeMirror fieldType = field.asType();
     TypeMirror listElementType = listElementType(fieldType);
     if (listElementType != null) {
       DtoBeanMeta nested = lookupByTarget(listElementType);
       if (nested != null) {
+        rejectConverterOnNested(field, converter, name, meta);
         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) {
+        rejectConverterOnNested(field, converter, name, meta);
         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);
   }
 
+  /**
+   * {@code @DtoConvert} only applies to {@code SCALAR}/{@code REF} value expressions
+   * ({@link DtoMapperWriter#propertyValueExpression}) - a {@code NESTED_ONE}/{@code NESTED_MANY}
+   * property's value comes entirely from its own nested mapper's {@code map(...)}/{@code
+   * mapList(...)} call, so a converter resolved for it would silently have no effect at all.
+   * Raise a compile error instead of letting the annotation quietly do nothing.
+   */
+  private void rejectConverterOnNested(VariableElement field, DtoConverterMeta converter, String name, DtoBeanMeta meta) {
+    if (converter != null) {
+      ctx.logError(field, "@DtoConvert on %s.%s has no effect - it isn't supported on a nested DTO"
+        + " graph property (NESTED_ONE/NESTED_MANY), only on SCALAR/REF properties. Remove"
+        + " @DtoConvert, or perform the conversion inside the nested DTO's own mapper instead.",
+        meta.targetFullName(), name);
+    }
+  }
+
   /**
    * 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
@@ -544,15 +666,54 @@ class DtoMappingReader {
       return null;
     }
     String methodName = prism.method();
-    ExecutableElement method = findMethod(converterType, methodName);
+    ExecutableElement method = findConverterMethod(field, 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);
   }
 
+  /**
+   * Resolve {@code @DtoConvert}'s {@code method()} on {@code converterType} - unlike
+   * {@link #findMethod}, this requires exactly one candidate taking a single parameter (the
+   * documented {@code @DtoConvert} contract: "taking the source property value and returning the
+   * converted DTO property value"). {@code findMethod} alone matches by simple name only, so a
+   * converter type with two same-named overloads (a very plausible shape for a shared conversion
+   * utility class, e.g. {@code format(Instant)} and {@code format(LocalDate)}) would silently bind
+   * to whichever one {@code ElementFilter.methodsIn} happens to return first, regardless of which
+   * one the developer actually intended - generating either a confusing compile error in the
+   * generated mapper (arity/type mismatch) or, worse, silently generating a call to the wrong
+   * overload if both happen to be call-compatible.
+   */
+  private ExecutableElement findConverterMethod(VariableElement field, TypeElement converterType, String methodName) {
+    List<ExecutableElement> oneArgCandidates = new ArrayList<>();
+    boolean anyNameMatch = false;
+    for (ExecutableElement candidate : ElementFilter.methodsIn(converterType.getEnclosedElements())) {
+      if (!candidate.getSimpleName().contentEquals(methodName)) {
+        continue;
+      }
+      anyNameMatch = true;
+      if (candidate.getParameters().size() == 1) {
+        oneArgCandidates.add(candidate);
+      }
+    }
+    if (oneArgCandidates.size() == 1) {
+      return oneArgCandidates.get(0);
+    }
+    if (oneArgCandidates.isEmpty()) {
+      ctx.logError(field, "@DtoConvert method \"%s\" not found on %s taking exactly one parameter%s",
+        methodName, converterType.getQualifiedName(),
+        anyNameMatch ? " (a method with that name exists but doesn't take exactly one parameter)" : "");
+      return null;
+    }
+    ctx.logError(field, "@DtoConvert method \"%s\" on %s is ambiguous - %d overloads take exactly one"
+      + " parameter, and @DtoConvert can't disambiguate by parameter type. Rename one of the"
+      + " overloads so the reference is unambiguous.",
+      methodName, converterType.getQualifiedName(), oneArgCandidates.size());
+    return null;
+  }
+
   private ExecutableElement findMethod(TypeElement type, String methodName) {
     for (ExecutableElement method : ElementFilter.methodsIn(type.getEnclosedElements())) {
       if (method.getSimpleName().contentEquals(methodName)) {
@@ -615,6 +776,29 @@ class DtoMappingReader {
     return getName;
   }
 
+  /**
+   * Whether {@code type} (searching {@code type} and its superclass chain) declares a field
+   * named {@code propertyName} - used to distinguish a real, fetchable Ebean bean property (which
+   * always has a backing field once enhanced) from a computed/derived getter with no backing
+   * storage at all (e.g. a hand-written method that filters/derives a value from other
+   * properties). {@code type == null} (unresolvable) conservatively returns {@code true} so an
+   * already-unresolvable segment doesn't also get flagged as "computed" - it'll already have
+   * fallen back to a guessed getter name via {@link #getterName}.
+   */
+  private boolean hasField(TypeElement type, String propertyName) {
+    if (type == null) {
+      return true;
+    }
+    for (TypeElement current = type; current != null; current = superclassOf(current)) {
+      for (VariableElement f : ElementFilter.fieldsIn(current.getEnclosedElements())) {
+        if (f.getSimpleName().contentEquals(propertyName)) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
   /**
    * 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
@@ -642,16 +826,61 @@ class DtoMappingReader {
    * which case later segments fall back to the guessed {@code getXxx()} name.
    */
   private TypeElement getterReturnType(TypeElement type, String getterMethodName) {
+    TypeMirror mirror = getterReturnTypeMirror(type, getterMethodName);
+    return mirror != null ? asTypeElement(mirror) : null;
+  }
+
+  /**
+   * As {@link #getterReturnType(TypeElement, String)}, but returns the raw {@link TypeMirror}
+   * rather than converting it to a {@link TypeElement} - needed by {@link #validateRequiresPath}
+   * to detect a {@code java.util.List}-typed return (via {@link #listElementType(TypeMirror)}),
+   * which {@link #getterReturnType(TypeElement, String)}'s {@code asTypeElement} conversion can't
+   * distinguish from any other declared type.
+   */
+  private TypeMirror getterReturnTypeMirror(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 method.getReturnType();
         }
       }
     }
     return null;
   }
 
+  /**
+   * Validate that every dot-notation segment of a declared {@code @DtoPath(requires = ...)}/
+   * {@code @DtoRef(requires = ...)} path value names a real, fetchable Ebean property (one with a
+   * backing field) on {@code source} - these are meant to be real entity fetch paths handed
+   * straight through to {@code FetchGroup.fetch(...)}, so a typo here would otherwise silently
+   * reintroduce the exact "compiles cleanly, fails at runtime with {@code PersistenceException}"
+   * problem the {@code requires()} escape hatch itself exists to prevent - it just wouldn't be
+   * caught until much later, since {@code requires()} paths are trusted verbatim rather than
+   * walked/checked like {@code @DtoPath#value()}'s own segments are. Handles a {@code List}-typed
+   * intermediate hop (e.g. {@code "currentMachine.organisationMachines"}) by unwrapping to the
+   * element type via {@link #listElementType(TypeMirror)}, mirroring how a real fetch path can
+   * traverse a collection.
+   */
+  private void validateRequiresPath(Element field, TypeElement source, String requiresPath, String annotationDisplay) {
+    TypeElement currentType = source;
+    for (String segment : requiresPath.split("\\.")) {
+      if (currentType == null) {
+        return; // already unresolvable upstream - don't cascade a confusing secondary error
+      }
+      if (!hasField(currentType, segment)) {
+        ctx.logError(field,
+          "%s names '%s' (in \"%s\") which has no backing field on %s - check for a typo, every"
+            + " requires() path segment must be a real, fetchable Ebean property.",
+          annotationDisplay, segment, requiresPath, currentType.getSimpleName());
+        return;
+      }
+      String getter = getterName(currentType, segment);
+      TypeMirror returnMirror = getterReturnTypeMirror(currentType, getter);
+      TypeMirror elementType = returnMirror != null ? listElementType(returnMirror) : null;
+      currentType = asTypeElement(elementType != null ? elementType : returnMirror);
+    }
+  }
+
   private TypeElement superclassOf(TypeElement type) {
     return asTypeElement(type.getSuperclass());
   }

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

@@ -25,18 +25,59 @@ class DtoPropertyMeta {
   private final List<String> sourcePropertyPath;
   private final DtoBeanMeta nested;
   private final DtoConverterMeta converter;
+  private final boolean primitiveTarget;
+  private final boolean failOnNull;
+  private final boolean computedSegment;
+  private final List<String> requiredFetchPaths;
 
   DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath, DtoBeanMeta nested) {
     this(dtoFieldName, kind, sourceGetterPath, sourcePropertyPath, nested, null);
   }
 
+  /**
+   * {@code NESTED_ONE}/{@code NESTED_MANY} constructor variant for a single-hop {@code @DtoPath}
+   * rename that traverses a computed/derived getter segment (no backing field) - see
+   * {@link #hasComputedSegment()}. Just as unfetchable via {@code FetchGroup.fetch(path, ...)} as
+   * the analogous {@link Kind#SCALAR} case, so it carries the same
+   * {@code computedSegment}/{@code requiredFetchPaths} through to {@code DtoMapperWriter}.
+   */
+  DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath,
+                  DtoBeanMeta nested, boolean computedSegment, List<String> requiredFetchPaths) {
+    this(dtoFieldName, kind, sourceGetterPath, sourcePropertyPath, nested, null, false, false, computedSegment, requiredFetchPaths);
+  }
+
   DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath, DtoBeanMeta nested, DtoConverterMeta converter) {
+    this(dtoFieldName, kind, sourceGetterPath, sourcePropertyPath, nested, converter, false, false);
+  }
+
+  DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath,
+                  DtoBeanMeta nested, DtoConverterMeta converter, boolean primitiveTarget, boolean failOnNull) {
+    this(dtoFieldName, kind, sourceGetterPath, sourcePropertyPath, nested, converter, primitiveTarget, failOnNull, false, List.of());
+  }
+
+  /**
+   * Full constructor - {@code primitiveTarget}/{@code failOnNull} only matter for a multi-hop
+   * ({@code sourceGetterPath.size() > 1}) {@link Kind#SCALAR}/{@link Kind#REF} property whose DTO
+   * field type is a Java primitive, per {@code @DtoPath#failOnNull()} - see
+   * {@link #sourceValueExpression(String)}. {@code computedSegment} is {@code true} only for a
+   * {@code @DtoPath} that traverses a computed/derived getter segment (no backing field) - see
+   * {@link #hasComputedSegment()}; kept separate from whether {@code requiredFetchPaths} happens
+   * to be empty, since {@code @DtoPath(requires = {})} legitimately declares "nothing extra
+   * needed" for a computed segment.
+   */
+  DtoPropertyMeta(String dtoFieldName, Kind kind, List<String> sourceGetterPath, List<String> sourcePropertyPath,
+                  DtoBeanMeta nested, DtoConverterMeta converter, boolean primitiveTarget, boolean failOnNull,
+                  boolean computedSegment, List<String> requiredFetchPaths) {
     this.dtoFieldName = dtoFieldName;
     this.kind = kind;
     this.sourceGetterPath = sourceGetterPath;
     this.sourcePropertyPath = sourcePropertyPath;
     this.nested = nested;
     this.converter = converter;
+    this.primitiveTarget = primitiveTarget;
+    this.failOnNull = failOnNull;
+    this.computedSegment = computedSegment;
+    this.requiredFetchPaths = requiredFetchPaths;
   }
 
   String dtoFieldName() {
@@ -79,11 +120,40 @@ class DtoPropertyMeta {
     return converter;
   }
 
+  /**
+   * {@code true} if this {@code @DtoPath} traverses a segment with no backing field (a computed/
+   * derived getter rather than a real, fetchable Ebean property) - in which case
+   * {@link #sourcePropertyPath()} must NOT be used to derive a {@code .fetch(path, "props")}
+   * ({@link Kind#SCALAR}) or {@code .fetch(path, mapper.fetchGroup())} ({@link Kind#NESTED_ONE}/
+   * {@link Kind#NESTED_MANY}) call (the path isn't a real Ebean fetch path), and
+   * {@link #requiredFetchPaths()} should be used instead (see {@code @DtoPath#requires()}).
+   */
+  boolean hasComputedSegment() {
+    return computedSegment;
+  }
+
+  /**
+   * Real entity paths that must be added to the {@code FetchGroup} to support this property's
+   * computed/derived getter segment - the real prefix path (if any) followed by the declared
+   * {@code @DtoPath#requires()} paths. Empty by default when {@link #hasComputedSegment()} is
+   * {@code false}; can also legitimately be empty when it's {@code true} (an explicit
+   * {@code @DtoPath(requires = {})} confirming nothing extra is needed).
+   */
+  List<String> requiredFetchPaths() {
+    return requiredFetchPaths;
+  }
+
   /**
    * 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())}.
+   * <p>
+   * That null-guarded chain always types as the boxed wrapper (one ternary branch is the
+   * {@code null} literal) - when {@link #primitiveTarget} is set (the DTO field is a Java
+   * primitive), the whole chain is additionally wrapped in a {@code DtoMapperSupport} call so it
+   * safely resolves to the primitive's zero-equivalent value (the default), or throws a clear
+   * exception instead, per {@code @DtoPath#failOnNull()} - see {@code DtoMapperSupport}.
    */
   String sourceValueExpression(String rootVariable) {
     if (sourceGetterPath.size() == 1) {
@@ -91,7 +161,23 @@ class DtoPropertyMeta {
     }
     StringBuilder sb = new StringBuilder();
     appendGuardedChain(sb, rootVariable, 0);
-    return sb.toString();
+    String chain = sb.toString();
+    if (!primitiveTarget) {
+      return chain;
+    }
+    return failOnNull
+      ? "DtoMapperSupport.require(" + chain + ", \"" + String.join(".", sourcePropertyPath) + "\")"
+      : "DtoMapperSupport.orZero(" + chain + ")";
+  }
+
+  /**
+   * {@code true} if {@link #sourceValueExpression(String)} wraps its chain in a
+   * {@code DtoMapperSupport} call - i.e. this is a multi-hop {@link Kind#SCALAR}/{@link Kind#REF}
+   * property whose DTO field type is primitive. Used to conditionally import
+   * {@code io.ebean.DtoMapperSupport} only when actually referenced.
+   */
+  boolean usesMapperSupport() {
+    return primitiveTarget && sourceGetterPath.size() > 1;
   }
 
   private void appendGuardedChain(StringBuilder sb, String prefix, int index) {
@@ -105,3 +191,4 @@ class DtoPropertyMeta {
     sb.append(')');
   }
 }
+

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

@@ -0,0 +1,814 @@
+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 {@code @DtoPath#requires()} - a {@code @DtoPath} traversing a segment with
+ * no backing field (a computed/derived getter, not a real fetchable Ebean property) must fail
+ * fast at compile time when {@code requires()} isn't specified, rather than compiling cleanly and
+ * failing later at runtime because the generated {@code FetchGroup} doesn't fetch whatever the
+ * getter itself needs internally (see docs/dto-mapping-design.md, "computed/derived getter"
+ * limitation).
+ * <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 (mirrors {@link DtoMapperFetchPathCollisionTest}).
+ */
+class DtoMapperComputedPathTest {
+
+  @Test
+  void dtoPathThroughComputedGetter_withoutRequires_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-computed-src");
+    Path outDir = Files.createTempDirectory("dto-computed-out");
+    writeSource(sourceDir, "org.tests.computed.Bar",
+      "package org.tests.computed;\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.computed.Foo",
+      "package org.tests.computed;\n"
+        + "\n"
+        + "import java.util.List;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private List<Bar> bars;\n"
+        + "\n"
+        + "  public List<Bar> getBars() { return bars; }\n"
+        + "\n"
+        + "  // computed/derived getter - no backing 'firstBar' field\n"
+        + "  public Bar getFirstBar() { return bars.isEmpty() ? null : bars.get(0); }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.computed.FooDto",
+      "package org.tests.computed;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoPath;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoPath(\"firstBar.name\")\n"
+        + "  private final String firstBarName;\n"
+        + "\n"
+        + "  public FooDto(String firstBarName) {\n"
+        + "    this.firstBarName = firstBarName;\n"
+        + "  }\n"
+        + "\n"
+        + "  public String getFirstBarName() { return firstBarName; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.computed.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.computed;\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 missing @DtoPath(requires = ...)");
+      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("no backing field")
+          && msg.contains("computed/derived getter")
+          && msg.contains("requires"));
+      assertTrue(matched, "expected the computed-getter requires() error message, got: " + errors);
+    }
+  }
+
+  /**
+   * Same defect as above, but exercising the {@code NESTED_ONE} branch rather than {@code SCALAR}
+   * - a single-hop {@code @DtoPath} rename whose target field type matches a separately registered
+   * nested DTO mapping. Prior to the fix, this case bypassed the computed-segment validation
+   * entirely (the nested-lookup branch returned early before it ran).
+   */
+  @Test
+  void dtoPathThroughComputedGetter_targetingNestedDto_withoutRequires_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-computed-nested-src");
+    Path outDir = Files.createTempDirectory("dto-computed-nested-out");
+    writeSource(sourceDir, "org.tests.computednested.Bar",
+      "package org.tests.computednested;\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.computednested.BarDto",
+      "package org.tests.computednested;\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.computednested.Foo",
+      "package org.tests.computednested;\n"
+        + "\n"
+        + "import java.util.List;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private List<Bar> bars;\n"
+        + "\n"
+        + "  public List<Bar> getBars() { return bars; }\n"
+        + "\n"
+        + "  // computed/derived getter - no backing 'firstBar' field\n"
+        + "  public Bar getFirstBar() { return bars.isEmpty() ? null : bars.get(0); }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.computednested.FooDto",
+      "package org.tests.computednested;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoPath;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoPath(\"firstBar\")\n"
+        + "  private final BarDto firstBar;\n"
+        + "\n"
+        + "  public FooDto(BarDto firstBar) {\n"
+        + "    this.firstBar = firstBar;\n"
+        + "  }\n"
+        + "\n"
+        + "  public BarDto getFirstBar() { return firstBar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.computednested.package-info",
+      "@DtoMapping(source = Bar.class, target = BarDto.class)\n"
+        + "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.computednested;\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 missing @DtoPath(requires = ...)");
+      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("no backing field")
+          && msg.contains("computed/derived getter")
+          && msg.contains("requires"));
+      assertTrue(matched, "expected the computed-getter requires() error message, got: " + errors);
+    }
+  }
+
+  /**
+   * Same defect class as the {@code @DtoPath} cases above, but for {@code @DtoRef} - a computed
+   * association getter with no backing field used via {@code @DtoRef} without {@code requires()}
+   * must fail fast at compile time rather than compile cleanly and fail later at runtime.
+   */
+  @Test
+  void dtoRefThroughComputedGetter_withoutRequires_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-ref-computed-src");
+    Path outDir = Files.createTempDirectory("dto-ref-computed-out");
+    writeSource(sourceDir, "org.tests.refcomputed.Bar",
+      "package org.tests.refcomputed;\n"
+        + "\n"
+        + "public class Bar {\n"
+        + "  private Long id;\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refcomputed.Foo",
+      "package org.tests.refcomputed;\n"
+        + "\n"
+        + "import java.util.List;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private List<Bar> bars;\n"
+        + "\n"
+        + "  public List<Bar> getBars() { return bars; }\n"
+        + "\n"
+        + "  // computed/derived getter - no backing 'firstBar' field\n"
+        + "  public Bar getFirstBar() { return bars.isEmpty() ? null : bars.get(0); }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refcomputed.FooDto",
+      "package org.tests.refcomputed;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoRef;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoRef\n"
+        + "  private final Long firstBarId;\n"
+        + "\n"
+        + "  public FooDto(Long firstBarId) {\n"
+        + "    this.firstBarId = firstBarId;\n"
+        + "  }\n"
+        + "\n"
+        + "  public Long getFirstBarId() { return firstBarId; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refcomputed.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.refcomputed;\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 missing @DtoRef(requires = ...)");
+      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("no backing field")
+          && msg.contains("computed/derived getter")
+          && msg.contains("requires"));
+      assertTrue(matched, "expected the computed-getter requires() error message, got: " + errors);
+    }
+  }
+
+  /**
+   * A {@code requires()} path value with a typo'd segment (not the computed segment itself, the
+   * developer-declared dependency path) must also fail fast at compile time - {@code requires()}
+   * values are handed straight through to {@code FetchGroup.fetch(...)}, so an unchecked typo
+   * there would silently reintroduce the exact runtime {@code PersistenceException} the whole
+   * escape hatch exists to prevent.
+   */
+  @Test
+  void dtoPathRequires_withTypoInPathValue_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-requires-typo-src");
+    Path outDir = Files.createTempDirectory("dto-requires-typo-out");
+    writeSource(sourceDir, "org.tests.requirestypo.Bar",
+      "package org.tests.requirestypo;\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.requirestypo.Foo",
+      "package org.tests.requirestypo;\n"
+        + "\n"
+        + "import java.util.List;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private List<Bar> bars;\n"
+        + "\n"
+        + "  public List<Bar> getBars() { return bars; }\n"
+        + "\n"
+        + "  // computed/derived getter - no backing 'firstBar' field\n"
+        + "  public Bar getFirstBar() { return bars.isEmpty() ? null : bars.get(0); }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.requirestypo.FooDto",
+      "package org.tests.requirestypo;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoPath;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  // 'barz' is a typo for the real 'bars' property\n"
+        + "  @DtoPath(value = \"firstBar.name\", requires = \"barz\")\n"
+        + "  private final String firstBarName;\n"
+        + "\n"
+        + "  public FooDto(String firstBarName) {\n"
+        + "    this.firstBarName = firstBarName;\n"
+        + "  }\n"
+        + "\n"
+        + "  public String getFirstBarName() { return firstBarName; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.requirestypo.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.requirestypo;\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 typo'd requires() path value");
+      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("no backing field")
+          && msg.contains("barz")
+          && msg.contains("typo"));
+      assertTrue(matched, "expected the requires() typo error message, got: " + errors);
+    }
+  }
+
+  /**
+   * Two {@code @DtoMixin} companion types targeting the same DTO class must fail fast at compile
+   * time - previously the second registration silently overwrote the first in
+   * {@code mixinsByTarget}, so whichever mixin was processed last would win with no diagnostic at
+   * all, silently discarding the other mixin's {@code @DtoPath}/{@code @DtoRef}/{@code @DtoConvert}
+   * overlays.
+   */
+  @Test
+  void duplicateDtoMixin_forSameTarget_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-mixin-dup-src");
+    Path outDir = Files.createTempDirectory("dto-mixin-dup-out");
+    writeSource(sourceDir, "org.tests.mixindup.FooDto",
+      "package org.tests.mixindup;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  private final String bar;\n"
+        + "\n"
+        + "  public FooDto(String bar) {\n"
+        + "    this.bar = bar;\n"
+        + "  }\n"
+        + "\n"
+        + "  public String getBar() { return bar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.mixindup.FooMixinA",
+      "package org.tests.mixindup;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoMixin;\n"
+        + "\n"
+        + "@DtoMixin(FooDto.class)\n"
+        + "interface FooMixinA {\n"
+        + "  String bar();\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.mixindup.FooMixinB",
+      "package org.tests.mixindup;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoMixin;\n"
+        + "\n"
+        + "@DtoMixin(FooDto.class)\n"
+        + "interface FooMixinB {\n"
+        + "  String bar();\n"
+        + "}\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 duplicate @DtoMixin for the same target");
+      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("Duplicate @DtoMixin") && msg.contains("FooDto"));
+      assertTrue(matched, "expected the duplicate @DtoMixin error message, got: " + errors);
+    }
+  }
+
+  /**
+   * A field carrying both {@code @DtoRef} and {@code @DtoPath} at once must fail fast at compile
+   * time - previously {@code resolveProperty()} checked {@code @DtoRef} first and returned early,
+   * silently ignoring any {@code @DtoPath} also present on the same field with no diagnostic,
+   * discarding whichever rename/path semantics the developer actually intended.
+   */
+  @Test
+  void dtoRefAndDtoPath_onSameField_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-ref-path-conflict-src");
+    Path outDir = Files.createTempDirectory("dto-ref-path-conflict-out");
+    writeSource(sourceDir, "org.tests.refpathconflict.Bar",
+      "package org.tests.refpathconflict;\n"
+        + "\n"
+        + "public class Bar {\n"
+        + "  private Long id;\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refpathconflict.Foo",
+      "package org.tests.refpathconflict;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private Bar bar;\n"
+        + "\n"
+        + "  public Bar getBar() { return bar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refpathconflict.FooDto",
+      "package org.tests.refpathconflict;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoPath;\n"
+        + "import io.ebean.annotation.DtoRef;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoRef\n"
+        + "  @DtoPath(\"bar.id\")\n"
+        + "  private final Long barId;\n"
+        + "\n"
+        + "  public FooDto(Long barId) {\n"
+        + "    this.barId = barId;\n"
+        + "  }\n"
+        + "\n"
+        + "  public Long getBarId() { return barId; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.refpathconflict.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.refpathconflict;\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 both @DtoRef and @DtoPath on the same field");
+      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("both @DtoRef and @DtoPath") && msg.contains("mutually exclusive"));
+      assertTrue(matched, "expected the @DtoRef/@DtoPath conflict error message, got: " + errors);
+    }
+  }
+
+  /**
+   * {@code @DtoConvert} on a {@code NESTED_ONE} (or {@code NESTED_MANY}) property must fail fast
+   * at compile time - previously the converter was resolved but simply never wired into the
+   * {@code NESTED_ONE}/{@code NESTED_MANY} {@link DtoPropertyMeta} constructor calls, so the
+   * annotation silently had zero effect (the nested mapper's own {@code map(...)} call always
+   * fully determines the value), with no diagnostic telling the developer it was ignored.
+   */
+  @Test
+  void dtoConvertOnNestedOne_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-convert-nested-src");
+    Path outDir = Files.createTempDirectory("dto-convert-nested-out");
+    writeSource(sourceDir, "org.tests.convertnested.Bar",
+      "package org.tests.convertnested;\n"
+        + "\n"
+        + "public class Bar {\n"
+        + "  private Long id;\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertnested.BarDto",
+      "package org.tests.convertnested;\n"
+        + "\n"
+        + "public class BarDto {\n"
+        + "  private final Long id;\n"
+        + "\n"
+        + "  public BarDto(Long id) {\n"
+        + "    this.id = id;\n"
+        + "  }\n"
+        + "\n"
+        + "  public Long getId() { return id; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertnested.Foo",
+      "package org.tests.convertnested;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private Bar bar;\n"
+        + "\n"
+        + "  public Bar getBar() { return bar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertnested.BarConverter",
+      "package org.tests.convertnested;\n"
+        + "\n"
+        + "public class BarConverter {\n"
+        + "  public static BarDto identity(BarDto dto) { return dto; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertnested.FooDto",
+      "package org.tests.convertnested;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoConvert;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoConvert(value = BarConverter.class, method = \"identity\")\n"
+        + "  private final BarDto bar;\n"
+        + "\n"
+        + "  public FooDto(BarDto bar) {\n"
+        + "    this.bar = bar;\n"
+        + "  }\n"
+        + "\n"
+        + "  public BarDto getBar() { return bar; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertnested.package-info",
+      "@DtoMapping(source = Bar.class, target = BarDto.class)\n"
+        + "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.convertnested;\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 @DtoConvert on a NESTED_ONE property");
+      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("@DtoConvert") && msg.contains("has no effect")
+          && msg.contains("nested DTO graph property"));
+      assertTrue(matched, "expected the @DtoConvert-on-nested error message, got: " + errors);
+    }
+  }
+
+  /**
+   * A {@code @DtoConvert(method = ...)} reference to a converter type with two overloads sharing
+   * that name, both taking exactly one parameter, must fail fast at compile time rather than
+   * silently binding to whichever overload {@code ElementFilter.methodsIn} happens to return
+   * first (unrelated to which one the developer actually meant) - {@code @DtoConvert} has no way
+   * to disambiguate by parameter type since it's declared by name alone.
+   */
+  @Test
+  void dtoConvertMethod_withAmbiguousOverloads_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-convert-ambiguous-src");
+    Path outDir = Files.createTempDirectory("dto-convert-ambiguous-out");
+    writeSource(sourceDir, "org.tests.convertambiguous.Foo",
+      "package org.tests.convertambiguous;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private String name;\n"
+        + "\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertambiguous.NameConverter",
+      "package org.tests.convertambiguous;\n"
+        + "\n"
+        + "public class NameConverter {\n"
+        + "  public static String format(String value) { return value; }\n"
+        + "  public static String format(Object value) { return String.valueOf(value); }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertambiguous.FooDto",
+      "package org.tests.convertambiguous;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoConvert;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoConvert(value = NameConverter.class, method = \"format\")\n"
+        + "  private final String name;\n"
+        + "\n"
+        + "  public FooDto(String name) {\n"
+        + "    this.name = name;\n"
+        + "  }\n"
+        + "\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertambiguous.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.convertambiguous;\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 ambiguous @DtoConvert method overloads");
+      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("ambiguous") && msg.contains("format") && msg.contains("2 overloads"));
+      assertTrue(matched, "expected the ambiguous @DtoConvert overload error message, got: " + errors);
+    }
+  }
+
+  /**
+   * A {@code @DtoConvert(method = ...)} reference to a method that exists on the converter type
+   * but doesn't take exactly one parameter (e.g. a zero-arg or two-arg overload sharing the name)
+   * must fail fast at compile time with a clear message, rather than {@code findMethod} matching
+   * it anyway and generating a call the compiler will reject with an unrelated arity-mismatch
+   * error in the generated mapper source.
+   */
+  @Test
+  void dtoConvertMethod_withWrongArity_expectCompileError() throws IOException {
+    Path sourceDir = Files.createTempDirectory("dto-convert-arity-src");
+    Path outDir = Files.createTempDirectory("dto-convert-arity-out");
+    writeSource(sourceDir, "org.tests.convertarity.Foo",
+      "package org.tests.convertarity;\n"
+        + "\n"
+        + "public class Foo {\n"
+        + "  private String name;\n"
+        + "\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertarity.NameConverter",
+      "package org.tests.convertarity;\n"
+        + "\n"
+        + "public class NameConverter {\n"
+        + "  public static String format() { return \"\"; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertarity.FooDto",
+      "package org.tests.convertarity;\n"
+        + "\n"
+        + "import io.ebean.annotation.DtoConvert;\n"
+        + "\n"
+        + "public class FooDto {\n"
+        + "  @DtoConvert(value = NameConverter.class, method = \"format\")\n"
+        + "  private final String name;\n"
+        + "\n"
+        + "  public FooDto(String name) {\n"
+        + "    this.name = name;\n"
+        + "  }\n"
+        + "\n"
+        + "  public String getName() { return name; }\n"
+        + "}\n");
+    writeSource(sourceDir, "org.tests.convertarity.package-info",
+      "@DtoMapping(source = Foo.class, target = FooDto.class)\n"
+        + "package org.tests.convertarity;\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 wrong-arity @DtoConvert method");
+      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("not found on") && msg.contains("exactly one parameter"));
+      assertTrue(matched, "expected the wrong-arity @DtoConvert 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);
+    }
+  }
+}

tests/pom.xml

@@ -4,7 +4,7 @@
   <parent>
     <artifactId>ebean-parent</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>tests</artifactId>

tests/test-dto-mapping/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <artifactId>tests</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>test-dto-mapping</artifactId>

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

@@ -49,4 +49,51 @@ public class Customer extends Model {
   public List<Contact> getContacts() {
     return contacts;
   }
+
+  /**
+   * Computed/derived getter (no backing field) - not a real Ebean property. Exercises
+   * {@code @DtoPath#requires()}: a {@code @DtoPath} traversing this segment must explicitly name
+   * {@code "contacts"} as a required fetch, since this method's own data dependency (the
+   * {@code contacts} collection) can't be inferred from the path string alone.
+   */
+  public Contact getPrimaryContact() {
+    return contacts.isEmpty() ? null : contacts.get(0);
+  }
+
+  /**
+   * Computed/derived getter (no backing field) deriving purely from {@code id} - which is always
+   * fetched as a matter of course, so unlike {@link #getPrimaryContact()} this one genuinely needs
+   * nothing extra fetched. Exercises {@code @DtoPath(requires = {})} (explicit empty array,
+   * confirming "nothing extra needed") as distinct from omitting {@code requires} entirely (a
+   * compile error).
+   */
+  public String getIdBadge() {
+    return "CUST-" + id;
+  }
+
+  /**
+   * Computed/derived getter (no backing field) reading {@code billingAddress.line1} - deliberately
+   * a different {@code Address} property to {@code city} (used narrowly elsewhere, see
+   * {@code FetchCollisionDto}), to exercise the priority between a bare, full {@code requires()}
+   * fetch of {@code billingAddress} and a sibling property's narrowed {@code fetch("billingAddress",
+   * "city")}: {@code FetchGroup}'s builder replaces (not merges) same-path fetch calls, so if the
+   * narrowed selection silently won, {@code line1} would never be loaded and calling this getter
+   * outside a persistence context would throw {@code LazyInitialisationException} instead of
+   * returning a value.
+   */
+  public String getBillingSummary() {
+    return billingAddress == null ? null : billingAddress.getLine1() + ", " + billingAddress.getCity();
+  }
+
+  /**
+   * Computed/derived getter (no backing field) returning a {@code List} - the {@code NESTED_MANY}
+   * counterpart to {@link #getPrimaryContact()}'s {@code NESTED_ONE} case. Exercises
+   * {@code @DtoPath#requires()} through a computed getter whose return type is a {@code List} of
+   * a type with its own registered nested DTO mapping - same underlying code path as
+   * {@code getPrimaryContact()} (single-hop computed segment, {@code DtoMapperWriter}'s
+   * {@code NESTED_ONE}/{@code NESTED_MANY} branch), just the collection variant.
+   */
+  public List<Contact> getRecentContacts() {
+    return contacts.isEmpty() ? List.of() : contacts.subList(0, Math.min(2, contacts.size()));
+  }
 }

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

@@ -0,0 +1,42 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Regression coverage for a single-hop {@code @DtoPath} rename traversing a computed/derived
+ * getter whose return type matches a <b>registered nested DTO mapping</b> - a variant of
+ * {@link ComputedPathDto} that exercises {@code DtoMapperWriter}'s {@code NESTED_ONE}/
+ * {@code NESTED_MANY} branch rather than its {@code SCALAR} branch.
+ * <p>
+ * {@code primaryContact} traverses {@code Customer#getPrimaryContact()} (no backing field - see
+ * {@link org.tests.dtomapping.model.Customer}), but its return type ({@code Contact}) has its own
+ * registered {@code @DtoMapping} to {@link ContactLeafDto} - so the field type here is
+ * {@code ContactLeafDto}, not a plain scalar. Without the fix, this single-hop case bypassed the
+ * computed-segment {@code requires()} validation entirely (the {@code NESTED_ONE} lookup returned
+ * early before it ran) and would have generated a broken {@code fetch("primaryContact",
+ * contactLeafMapper.fetchGroup())} call - {@code "primaryContact"} isn't a real Ebean fetch path,
+ * so that would fail at runtime with {@code PersistenceException: No property found}.
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = ComputedNestedDto.class)} is declared on
+ * {@code package-info.java}.
+ */
+public class ComputedNestedDto {
+
+  private final Long id;
+
+  @DtoPath(value = "primaryContact", requires = "contacts")
+  private final ContactLeafDto primaryContact;
+
+  public ComputedNestedDto(Long id, ContactLeafDto primaryContact) {
+    this.id = id;
+    this.primaryContact = primaryContact;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public ContactLeafDto getPrimaryContact() {
+    return primaryContact;
+  }
+}

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

@@ -0,0 +1,42 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+import java.util.List;
+
+/**
+ * Regression coverage for a single-hop {@code @DtoPath} rename traversing a computed/derived
+ * getter whose return type is a {@code List} matching a <b>registered nested DTO mapping</b> -
+ * the {@code NESTED_MANY} counterpart to {@link ComputedNestedDto}'s {@code NESTED_ONE} case.
+ * <p>
+ * {@code recentContacts} traverses {@code Customer#getRecentContacts()} (no backing field - see
+ * {@link org.tests.dtomapping.model.Customer}), returning a {@code List<Contact>} - its element
+ * type has its own registered {@code @DtoMapping} to {@link ContactLeafDto}, so the field type
+ * here is {@code List<ContactLeafDto>}. Shares the exact same codegen path as
+ * {@link ComputedNestedDto} ({@code DtoMapperWriter}'s {@code NESTED_ONE}/{@code NESTED_MANY}
+ * branch both route computed segments to {@code extraFetchPaths} identically) - this is coverage
+ * confirming the {@code NESTED_MANY} variant actually works end-to-end, not a bug fix.
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = ComputedNestedListDto.class)} is declared
+ * on {@code package-info.java}.
+ */
+public class ComputedNestedListDto {
+
+  private final Long id;
+
+  @DtoPath(value = "recentContacts", requires = "contacts")
+  private final List<ContactLeafDto> recentContacts;
+
+  public ComputedNestedListDto(Long id, List<ContactLeafDto> recentContacts) {
+    this.id = id;
+    this.recentContacts = recentContacts;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public List<ContactLeafDto> getRecentContacts() {
+    return recentContacts;
+  }
+}

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

@@ -0,0 +1,41 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Regression coverage for {@code @DtoPath#requires()} - {@code primaryContactLastName} traverses
+ * {@code Customer#getPrimaryContact()}, a computed/derived getter with no backing field (it picks
+ * the first entry out of the {@code contacts} collection). Since the generator can't infer that
+ * this getter's own data dependency is {@code contacts}, {@code requires = "contacts"} declares it
+ * explicitly so the generated {@code FetchGroup} includes a bare {@code fetch("contacts")} call -
+ * without it, {@code getPrimaryContact()} would run against an unfetched/lazy collection and either
+ * fail or trigger an extra lazy-load query at map time.
+ * <p>
+ * See {@link org.tests.dtomapping.TestComputedPath} and {@code
+ * DtoMapperComputedPathTest} (querybean-generator module) for the companion negative case - the
+ * same shape of {@code @DtoPath} but with {@code requires} omitted, which must be a compile-time
+ * error rather than a silent runtime failure.
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = ComputedPathDto.class)} is declared on
+ * {@code package-info.java}.
+ */
+public class ComputedPathDto {
+
+  private final Long id;
+
+  @DtoPath(value = "primaryContact.lastName", requires = "contacts")
+  private final String primaryContactLastName;
+
+  public ComputedPathDto(Long id, String primaryContactLastName) {
+    this.id = id;
+    this.primaryContactLastName = primaryContactLastName;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getPrimaryContactLastName() {
+    return primaryContactLastName;
+  }
+}

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

@@ -0,0 +1,36 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Regression coverage for {@code @DtoPath(requires = {})} - {@code idBadge} traverses {@code
+ * Customer#getIdBadge()}, a computed/derived getter with no backing field, but one that genuinely
+ * needs nothing extra fetched (it derives purely from {@code id}, which is always fetched as a
+ * matter of course). The explicit empty array confirms that to the generator, as opposed to
+ * omitting {@code requires} entirely (a compile error - see {@link ComputedPathDto} for the case
+ * that does need a real fetch path, and {@code DtoMapperComputedPathTest} in the
+ * querybean-generator module for the negative/omitted case).
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = ComputedPathNoFetchDto.class)} is declared
+ * on {@code package-info.java}.
+ */
+public class ComputedPathNoFetchDto {
+
+  private final Long id;
+
+  @DtoPath(value = "idBadge", requires = {})
+  private final String idBadge;
+
+  public ComputedPathNoFetchDto(Long id, String idBadge) {
+    this.id = id;
+    this.idBadge = idBadge;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getIdBadge() {
+    return idBadge;
+  }
+}

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

@@ -0,0 +1,41 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoRef;
+
+/**
+ * Regression coverage for {@code @DtoRef} traversing a computed/derived association getter (no
+ * backing field) - a variant of {@link ComputedPathDto} that exercises {@code @DtoRef}'s
+ * {@code Kind.REF} branch rather than {@code @DtoPath}'s {@code SCALAR}/{@code NESTED_ONE}
+ * branches.
+ * <p>
+ * {@code primaryContactId} derives its association name ("primaryContact") from the field name,
+ * which resolves to {@code Customer#getPrimaryContact()} - a computed getter with no backing
+ * field (see {@link org.tests.dtomapping.model.Customer}). Without the fix, {@code @DtoRef} never
+ * checked whether the association had a backing field at all, so this compiled cleanly and
+ * generated a broken {@code FetchGroup.select("primaryContact")} call - {@code "primaryContact"}
+ * isn't a real Ebean property, so that would fail at runtime with {@code PersistenceException: No
+ * property found}.
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = ComputedRefDto.class)} is declared on
+ * {@code package-info.java}.
+ */
+public class ComputedRefDto {
+
+  private final Long id;
+
+  @DtoRef(requires = "contacts")
+  private final Long primaryContactId;
+
+  public ComputedRefDto(Long id, Long primaryContactId) {
+    this.id = id;
+    this.primaryContactId = primaryContactId;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public Long getPrimaryContactId() {
+    return primaryContactId;
+  }
+}

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

@@ -0,0 +1,36 @@
+package org.tests.dtomapping;
+
+/**
+ * Minimal "leaf" DTO for {@link org.tests.dtomapping.model.Contact} - deliberately has no further
+ * nested relations of its own (unlike {@link ContactDto}, which also maps {@code customer}), so
+ * {@link ComputedNestedDto}'s bare {@code fetch("contacts")} (everything {@code Contact} itself
+ * owns, no deeper paths) is sufficient to satisfy it without needing to reason about propagating a
+ * nested mapper's own fetch requirements up through a computed getter - see {@link ComputedNestedDto}.
+ * <p>
+ * {@code @DtoMapping(source = Contact.class, target = ContactLeafDto.class)} is declared on
+ * {@code package-info.java}.
+ */
+public class ContactLeafDto {
+
+  private final Long id;
+  private final String firstName;
+  private final String lastName;
+
+  public ContactLeafDto(Long id, String firstName, String lastName) {
+    this.id = id;
+    this.firstName = firstName;
+    this.lastName = lastName;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getFirstName() {
+    return firstName;
+  }
+
+  public String getLastName() {
+    return lastName;
+  }
+}

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

@@ -0,0 +1,49 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Regression coverage for the priority between a bare, full {@code requires()} fetch and a
+ * sibling property's narrowed {@code @DtoPath} fetch of the exact same path - see
+ * {@link org.tests.dtomapping.model.Customer#getBillingSummary()}.
+ * <p>
+ * {@code billingCity} narrows the {@code billingAddress} fetch down to just {@code city} (a plain
+ * {@code @DtoPath("billingAddress.city")}). {@code billingSummary} traverses the computed
+ * {@code getBillingSummary()} getter (no backing field), declaring {@code requires =
+ * "billingAddress"} - a bare, full fetch of the exact same path. {@code FetchGroup}'s builder
+ * replaces (not merges) same-path fetch calls, so without prioritizing the full fetch over the
+ * narrow one, {@code line1} (needed internally by {@code getBillingSummary()}, but not by
+ * {@code billingCity}) would silently never be loaded - calling {@code getBillingSummary()} would
+ * then throw {@code LazyInitialisationException} rather than return a value.
+ * <p>
+ * {@code @DtoMapping(source = Customer.class, target = FetchCollisionDto.class)} is declared on
+ * {@code package-info.java}.
+ */
+public class FetchCollisionDto {
+
+  private final Long id;
+
+  @DtoPath("billingAddress.city")
+  private final String billingCity;
+
+  @DtoPath(value = "billingSummary", requires = "billingAddress")
+  private final String billingSummary;
+
+  public FetchCollisionDto(Long id, String billingCity, String billingSummary) {
+    this.id = id;
+    this.billingCity = billingCity;
+    this.billingSummary = billingSummary;
+  }
+
+  public Long getId() {
+    return id;
+  }
+
+  public String getBillingCity() {
+    return billingCity;
+  }
+
+  public String getBillingSummary() {
+    return billingSummary;
+  }
+}

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

@@ -0,0 +1,31 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Regression coverage for a primitive-typed DTO field derived via a multi-hop {@code @DtoPath}
+ * through a <b>nullable</b> ToOne relation ({@code Customer#getBillingAddress()} can be
+ * {@code null}) - the generated null-guarded getter chain (e.g. {@code (x == null ? null :
+ * x.getId())}) types as boxed {@code Long}, which would auto-unbox to a {@code
+ * NullPointerException} when passed to a primitive constructor parameter if not handled.
+ * <p>
+ * {@code billingAddressId} exercises the default behaviour (silently defaults to {@code 0}) - see
+ * {@link org.tests.dtomapping.PrimitiveNullPathFailOnNullDto} for the {@code failOnNull = true}
+ * counterpart, and {@link org.tests.dtomapping.TestPrimitiveNullPath} for both cases.
+ * <p>
+ * {@code @DtoMapping(source = Contact.class, target = PrimitiveNullPathDto.class)} is declared
+ * on {@code package-info.java}.
+ */
+public class PrimitiveNullPathDto {
+
+  @DtoPath("customer.billingAddress.id")
+  private final long billingAddressId;
+
+  public PrimitiveNullPathDto(long billingAddressId) {
+    this.billingAddressId = billingAddressId;
+  }
+
+  public long getBillingAddressId() {
+    return billingAddressId;
+  }
+}

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

@@ -0,0 +1,26 @@
+package org.tests.dtomapping;
+
+import io.ebean.annotation.DtoPath;
+
+/**
+ * Companion to {@link PrimitiveNullPathDto} isolating {@code @DtoPath(failOnNull = true)} in its
+ * own DTO type - kept separate so a null intermediate hop's exception doesn't also abort
+ * construction of {@link PrimitiveNullPathDto}'s default (silently-zero) field in the same
+ * constructor call. See {@link org.tests.dtomapping.TestPrimitiveNullPath}.
+ * <p>
+ * {@code @DtoMapping(source = Contact.class, target = PrimitiveNullPathFailOnNullDto.class)} is
+ * declared on {@code package-info.java}.
+ */
+public class PrimitiveNullPathFailOnNullDto {
+
+  @DtoPath(value = "customer.billingAddress.id", failOnNull = true)
+  private final long billingAddressId;
+
+  public PrimitiveNullPathFailOnNullDto(long billingAddressId) {
+    this.billingAddressId = billingAddressId;
+  }
+
+  public long getBillingAddressId() {
+    return billingAddressId;
+  }
+}

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

@@ -0,0 +1,34 @@
+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;
+
+/**
+ * Regression test for {@link ComputedNestedListDto} - see its javadoc.
+ */
+class TestComputedNestedListPath {
+
+  @Test
+  void mapTo_whenComputedGetterReturnsListTargetingNestedDto_requiresFetchesItsDependency() {
+    Customer customer = new Customer("ComputedNestedListCo");
+    customer.save();
+    Contact alice = new Contact("Alice", "Smith", customer);
+    alice.save();
+    Contact bob = new Contact("Bob", "Jones", customer);
+    bob.save();
+
+    ComputedNestedListDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(ComputedNestedListDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getRecentContacts()).hasSize(2);
+    assertThat(dto.getRecentContacts().get(0).getFirstName()).isEqualTo("Alice");
+    assertThat(dto.getRecentContacts().get(1).getFirstName()).isEqualTo("Bob");
+  }
+}

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

@@ -0,0 +1,32 @@
+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;
+
+/**
+ * Regression test for {@link ComputedNestedDto} - see its javadoc.
+ */
+class TestComputedNestedPath {
+
+  @Test
+  void mapTo_whenComputedGetterTargetsNestedDto_requiresFetchesItsDependency() {
+    Customer customer = new Customer("ComputedNestedCo");
+    customer.save();
+    Contact contact = new Contact("Bob", "Jones", customer);
+    contact.save();
+
+    ComputedNestedDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(ComputedNestedDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getPrimaryContact()).isNotNull();
+    assertThat(dto.getPrimaryContact().getFirstName()).isEqualTo("Bob");
+    assertThat(dto.getPrimaryContact().getLastName()).isEqualTo("Jones");
+  }
+}

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

@@ -0,0 +1,32 @@
+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;
+
+/**
+ * Regression test for {@link ComputedPathDto} (the {@code @DtoPath#requires()} happy path) - see
+ * its javadoc, and {@code DtoMapperComputedPathTest} (querybean-generator module) for the
+ * companion negative/compile-error case.
+ */
+class TestComputedPath {
+
+  @Test
+  void mapTo_whenPathTraversesComputedGetter_requiresFetchesItsDependency() {
+    Customer customer = new Customer("ComputedPathCo");
+    customer.save();
+    Contact contact = new Contact("Alice", "Smith", customer);
+    contact.save();
+
+    ComputedPathDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(ComputedPathDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getPrimaryContactLastName()).isEqualTo("Smith");
+  }
+}

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

@@ -0,0 +1,28 @@
+package org.tests.dtomapping;
+
+import io.ebean.DB;
+import org.junit.jupiter.api.Test;
+import org.tests.dtomapping.model.Customer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Regression test for {@link ComputedPathNoFetchDto} (the {@code @DtoPath(requires = {})} explicit
+ * empty case) - see its javadoc.
+ */
+class TestComputedPathNoFetch {
+
+  @Test
+  void mapTo_whenComputedGetterNeedsNoExtraFetch_explicitEmptyRequiresWorks() {
+    Customer customer = new Customer("NoExtraFetchCo");
+    customer.save();
+
+    ComputedPathNoFetchDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(ComputedPathNoFetchDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getIdBadge()).isEqualTo("CUST-" + customer.getId());
+  }
+}

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

@@ -0,0 +1,30 @@
+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;
+
+/**
+ * Regression test for {@link ComputedRefDto} - see its javadoc.
+ */
+class TestComputedRefPath {
+
+  @Test
+  void mapTo_whenDtoRefTraversesComputedGetter_requiresFetchesItsDependency() {
+    Customer customer = new Customer("ComputedRefCo");
+    customer.save();
+    Contact contact = new Contact("Alice", "Smith", customer);
+    contact.save();
+
+    ComputedRefDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(ComputedRefDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getPrimaryContactId()).isEqualTo(contact.getId());
+  }
+}

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

@@ -0,0 +1,37 @@
+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;
+
+/**
+ * Regression test for {@link FetchCollisionDto} - see its javadoc. Proves the fix for the
+ * priority between a bare, full {@code requires()} fetch and a sibling property's narrowed
+ * {@code @DtoPath} fetch of the exact same path: without it, this test fails with
+ * {@code LazyInitialisationException} ("line1" unfetched) rather than the assertions below.
+ */
+class TestFetchCollisionPath {
+
+  @Test
+  void mapTo_whenBareRequiresPathCollidesWithNarrowedSiblingFetch_fullFetchWins() {
+    Address address = new Address("221B Baker Street", "London");
+    address.save();
+    Customer customer = new Customer("FetchCollisionCo");
+    customer.setBillingAddress(address);
+    customer.save();
+
+    FetchCollisionDto dto = DB.find(Customer.class)
+      .where().idEq(customer.getId())
+      .mapTo(FetchCollisionDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getBillingCity()).isEqualTo("London");
+    // only satisfiable if billingAddress was fully (not narrowly) fetched - line1 isn't part of
+    // the sibling billingCity property's own narrowed fetch("billingAddress", "city")
+    assertThat(dto.getBillingSummary()).isEqualTo("221B Baker Street, London");
+  }
+}

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

@@ -0,0 +1,47 @@
+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;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Regression test for {@link PrimitiveNullPathDto} - see its javadoc.
+ */
+class TestPrimitiveNullPath {
+
+  @Test
+  void mapTo_whenNullableRelationHopIsNull_defaultsPrimitiveToZero() {
+    Customer customer = new Customer("NoBillingAddressCo");
+    // deliberately leave billingAddress null
+    customer.save();
+    Contact contact = new Contact("Jane", "Doe", customer);
+    contact.save();
+
+    PrimitiveNullPathDto dto = DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(PrimitiveNullPathDto.class)
+      .findOne();
+
+    assertThat(dto).isNotNull();
+    assertThat(dto.getBillingAddressId()).isZero();
+  }
+
+  @Test
+  void mapTo_whenNullableRelationHopIsNull_andFailOnNull_throws() {
+    Customer customer = new Customer("NoBillingAddressCo2");
+    customer.save();
+    Contact contact = new Contact("John", "Doe", customer);
+    contact.save();
+
+    assertThatThrownBy(() -> DB.find(Contact.class)
+      .where().idEq(contact.getId())
+      .mapTo(PrimitiveNullPathFailOnNullDto.class)
+      .findOne())
+      .isInstanceOf(IllegalStateException.class)
+      .hasMessageContaining("customer.billingAddress.id");
+  }
+}

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

@@ -50,6 +50,15 @@
 @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)
+@DtoMapping(source = Contact.class, target = PrimitiveNullPathDto.class)
+@DtoMapping(source = Contact.class, target = PrimitiveNullPathFailOnNullDto.class)
+@DtoMapping(source = Customer.class, target = ComputedPathDto.class)
+@DtoMapping(source = Customer.class, target = ComputedPathNoFetchDto.class)
+@DtoMapping(source = Contact.class, target = ContactLeafDto.class)
+@DtoMapping(source = Customer.class, target = ComputedNestedDto.class)
+@DtoMapping(source = Customer.class, target = ComputedNestedListDto.class)
+@DtoMapping(source = Customer.class, target = ComputedRefDto.class)
+@DtoMapping(source = Customer.class, target = FetchCollisionDto.class)
 package org.tests.dtomapping;
 
 import io.ebean.annotation.DtoMapping;

tests/test-java16/pom.xml

@@ -5,7 +5,7 @@
   <parent>
     <artifactId>tests</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>test-java16</artifactId>

tests/test-kotlin/pom.xml

@@ -6,7 +6,7 @@
   <parent>
     <artifactId>tests</artifactId>
     <groupId>io.ebean</groupId>
-    <version>18.2.0</version>
+    <version>18.3.0</version>
   </parent>
 
   <artifactId>test-kotlin</artifactId>
@@ -40,7 +40,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
     </dependency>
 
     <dependency>
@@ -53,7 +53,7 @@
     <dependency>
       <groupId>io.ebean</groupId>
       <artifactId>ebean-test</artifactId>
-      <version>18.2.0</version>
+      <version>18.3.0</version>
       <scope>test</scope>
     </dependency>