enh: Add findSingleAttributeOrEmpty() returning Optional

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

@@ -970,6 +970,25 @@ public interface Query<T> extends CancelableQuery {
   @Nullable
   <A> A findSingleAttribute();
 
+  /**
+   * Execute the query returning a single optional attribute value.
+   * <p>
+   * <h3>Example</h3>
+   * <pre>{@code
+   *
+   *  Optional<String> maybeName =
+   *    new QCustomer()
+   *      .select(name)
+   *      .id.eq(42)
+   *      .status.eq(NEW)
+   *      .findSingleAttributeOrEmpty();
+   *
+   * }</pre>
+   *
+   * @return an optional value for the selected property
+   */
+  <A> Optional<A> findSingleAttributeOrEmpty();
+
   /**
    * Return true if this is countDistinct query.
    */

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

@@ -305,6 +305,11 @@ final class DefaultFetchGroupQuery<T> implements SpiFetchGroupQuery<T>, SpiQuery
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
   }
 
+  @Override
+  public <A> Optional<A> findSingleAttributeOrEmpty() {
+    throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");
+  }
+
   @Override
   public boolean isCountDistinct() {
     throw new RuntimeException("EB102: Only select() and fetch() clause is allowed on FetchGroup");

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

@@ -1161,7 +1161,7 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
     // add the rawSql statement - if any
     if (orderByIsEmpty()) {
       if (rawSql != null && rawSql.getSql() != null) {
-        order(rawSql.getSql().getOrderBy());
+        orderBy(rawSql.getSql().getOrderBy());
       }
     }
     if (checkPagingOrderBy()) {
@@ -1517,7 +1517,6 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
   }
 
   @Override
-  @SuppressWarnings("unchecked")
   public final <A> List<A> findSingleAttributeList() {
     return server.findSingleAttributeList(this);
   }
@@ -1533,6 +1532,11 @@ public class DefaultOrmQuery<T> extends AbstractQuery implements SpiQuery<T> {
     return !list.isEmpty() ? list.get(0) : null;
   }
 
+  @Override
+  public final <A> Optional<A> findSingleAttributeOrEmpty() {
+    return Optional.ofNullable(findSingleAttribute());
+  }
+
   @Override
   public final T findOne() {
     return server.findOne(this);

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

@@ -1867,6 +1867,28 @@ public abstract class TQRootBean<T, R> {
     return query.findSingleAttribute();
   }
 
+  /**
+   * Execute the query returning a single optional attribute value.
+   * <p>
+   * <h3>Example</h3>
+   * <pre>{@code
+   *
+   *  Optional<String> maybeName =
+   *    new QCustomer()
+   *      .select(name)
+   *      .id.eq(42)
+   *      .status.eq(NEW)
+   *      .findSingleAttributeOrEmpty();
+   *
+   * }</pre>
+   *
+   * @return an optional value for the selected property
+   */
+  @Nullable
+  public <A> Optional<A> findSingleAttributeOrEmpty() {
+    return query.findSingleAttributeOrEmpty();
+  }
+
   /**
    * Execute the query processing the beans one at a time.
    * <p>

ebean-querybean/src/test/java/org/querytest/QCustomerTest.java

@@ -1069,6 +1069,32 @@ public class QCustomerTest {
     assertThat(maxDate).isNotNull();
   }
 
+  @Test
+  public void findSingleAttributeOrEmpty() {
+
+    Customer cust = new Customer();
+    cust.setName("MaybeIExist yeah");
+    cust.setStatus(Customer.Status.GOOD);
+    cust.setRegistered(new Date());
+    cust.save();
+
+    Optional<String> customerName = new QCustomer()
+      .select(name)
+      .status.eq(Customer.Status.GOOD)
+      .name.startsWith("MaybeIExist")
+      .findSingleAttributeOrEmpty();
+
+    assertThat(customerName).isPresent();
+
+    Optional<String> customerName2 = new QCustomer()
+      .select(name)
+      .status.eq(Customer.Status.GOOD)
+      .name.eq("NahIDoNotExist")
+      .findSingleAttributeOrEmpty();
+
+    assertThat(customerName2).isEmpty();
+  }
+
 
   @Test
   public void testFetchByScalarValue() {

ebean-test/src/test/java/org/tests/query/other/TestQuerySingleAttribute.java

@@ -20,6 +20,7 @@ import org.tests.o2m.OmBasicParent;
 import java.sql.Date;
 import java.time.LocalDate;
 import java.util.List;
+import java.util.Optional;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -139,6 +140,32 @@ class TestQuerySingleAttribute extends BaseTestCase {
     assertThat(name).isNotNull();
   }
 
+  @Test
+  void findSingleAttributeOrEmpty() {
+    ResetBasicData.reset();
+
+    Query<Customer> query = DB.find(Customer.class)
+      .select("name")
+      .where().eq("name", "Rob").query();
+
+    Optional<String> name = query.findSingleAttributeOrEmpty();
+
+    assertThat(sqlOf(query)).contains("select t0.name from o_customer t0");
+    assertThat(name).isPresent().contains("Rob");
+  }
+
+  @Test
+  void findSingleAttributeOrEmpty_when_empty() {
+    ResetBasicData.reset();
+
+    Query<Customer> query = DB.find(Customer.class)
+      .select("name")
+      .where().eq("name", "I_Do_Not_ExistO!").query();
+
+    Optional<String> name = query.findSingleAttributeOrEmpty();
+    assertThat(name).isEmpty();
+  }
+
   @Test
   void findSingleAttributeList_with_join_column() {
     ResetBasicData.reset();