Adopt to changed Hibernate behavior returning domain types using tuple queries.

We now allow using the domain type when it is returned from a tuple query. This allows projections if the return value is not a Map.

Closes #2815

Author: mp911de

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/AbstractJpaQuery.java

@@ -314,18 +314,17 @@ public TupleConverter(ReturnedType type) {
 		@Override
 		public Object convert(Object source) {
 
-			if (!(source instanceof Tuple)) {
+			if (!(source instanceof Tuple tuple)) {
 				return source;
 			}
 
-			Tuple tuple = (Tuple) source;
 			List<TupleElement<?>> elements = tuple.getElements();
 
 			if (elements.size() == 1) {
 
 				Object value = tuple.get(elements.get(0));
 
-				if (type.isInstance(value) || value == null) {
+				if (type.getDomainType().isInstance(value) || type.isInstance(value) || value == null) {
 					return value;
 				}
 			}

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/UserRepositoryFinderTests.java

@@ -39,6 +39,8 @@
 import org.springframework.data.jpa.provider.PersistenceProvider;
 import org.springframework.data.jpa.repository.sample.RoleRepository;
 import org.springframework.data.jpa.repository.sample.UserRepository;
+import org.springframework.data.jpa.repository.sample.UserRepository.IdOnly;
+import org.springframework.data.jpa.repository.sample.UserRepository.RolesAndFirstname;
 import org.springframework.data.repository.query.QueryLookupStrategy;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
@@ -276,11 +278,28 @@ void translatesNotContainsToNotMemberOf() {
 				.containsExactlyInAnyOrder(dave, oliver);
 	}
 
-	@Test // DATAJPA-974
+	@Test // DATAJPA-974, GH-2815
 	void executesQueryWithProjectionContainingReferenceToPluralAttribute() {
 
-		assertThat(userRepository.findRolesAndFirstnameBy()) //
+		List<RolesAndFirstname> rolesAndFirstnameBy = userRepository.findRolesAndFirstnameBy();
+
+		assertThat(rolesAndFirstnameBy)
 				.isNotNull();
+
+		for (RolesAndFirstname rolesAndFirstname : rolesAndFirstnameBy) {
+			assertThat(rolesAndFirstname.getFirstname()).isNotNull();
+			assertThat(rolesAndFirstname.getRoles()).isNotNull();
+		}
+	}
+
+	@Test // GH-2815
+	void executesQueryWithProjectionThroughStringQuery() {
+
+		List<IdOnly> ids = userRepository.findIdOnly();
+
+		assertThat(ids).isNotNull();
+
+		assertThat(ids).extracting(IdOnly::getId).doesNotContainNull();
 	}
 
 	@Test // DATAJPA-1023, DATACMNS-959

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java

@@ -551,6 +551,9 @@ List<User> findUsersByFirstnameForSpELExpressionWithParameterIndexOnlyWithEntity
 
 	List<RolesAndFirstname> findRolesAndFirstnameBy();
 
+	@Query(value = "FROM User u")
+	List<IdOnly> findIdOnly();
+
 	// DATAJPA-1172
 	@Query("select u from User u where u.age = :age")
 	List<User> findByStringAge(@Param("age") String age);
@@ -721,4 +724,8 @@ interface NameOnly {
 	interface EmailOnly {
 		String getEmailAddress();
 	}
+
+	interface IdOnly {
+		int getId();
+	}
 }