Refine input property handling for DTO projections.

We now retain the input property ordering. Additionally, when providing input properties, we no longer limit properties to top-level properties but allow selection of nested properties.

Closes #4174
See: #3908

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/FluentQuerySupport.java

@@ -18,6 +18,7 @@ package org.springframework.data.jpa.repository.support;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.Set;
 import java.util.function.Function;
 
@@ -60,7 +61,7 @@ abstract class FluentQuerySupport<S, R> {
 		this.limit = limit;
 
 		if (properties != null) {
-			this.properties = new HashSet<>(properties);
+			this.properties = new LinkedHashSet<>(properties);
 		} else {
 			this.properties = Collections.emptySet();
 		}

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@@ -788,13 +788,14 @@ public class SimpleJpaRepository<T, ID> implements JpaRepositoryImplementation<T
 	 * @param inputProperties must not be {@literal null}.
 	 * @param scrollPosition must not be {@literal null}.
 	 */
-	private <S extends T> TypedQuery<S> getQuery(ReturnedType returnedType, @Nullable Specification<S> spec,
-			Class<S> domainClass, Sort sort, Collection<String> inputProperties, @Nullable ScrollPosition scrollPosition) {
+	private <S extends T> TypedQuery<S> getQuery(ReturnedType returnedType, @Nullable Specification<S> spec, Class<S> domainClass,
+			Sort sort, Collection<String> inputProperties, @Nullable ScrollPosition scrollPosition) {
 
 		CriteriaBuilder builder = entityManager.getCriteriaBuilder();
 		CriteriaQuery<S> query;
 
 		boolean interfaceProjection = returnedType.isInterfaceProjection();
+		boolean inputPropertiesPresent = !inputProperties.isEmpty();
 
 		if (returnedType.needsCustomConstruction()) {
 			query = (CriteriaQuery) (interfaceProjection ? builder.createTupleQuery()
@@ -822,15 +823,21 @@ public class SimpleJpaRepository<T, ID> implements JpaRepositoryImplementation<T
 			Set<String> topLevelProperties = new HashSet<>();
 			for (String property : requiredSelection) {
 
-				int separator = property.indexOf('.');
-				String topLevelProperty = separator == -1 ? property : property.substring(0, separator);
+				if (inputPropertiesPresent && !interfaceProjection) {
+					PropertyPath path = PropertyPath.from(property, returnedType.getDomainType());
+					selections.add(QueryUtils.toExpressionRecursively(root, path, true));
+				} else {
 
-				if (!topLevelProperties.add(topLevelProperty)) {
-					continue;
-				}
+					int separator = property.indexOf('.');
+					String topLevelProperty = separator == -1 ? property : property.substring(0, separator);
+
+					if (!topLevelProperties.add(topLevelProperty)) {
+						continue;
+					}
 
-				PropertyPath path = PropertyPath.from(topLevelProperty, returnedType.getDomainType());
-				selections.add(QueryUtils.toExpressionRecursively(root, path, true).alias(topLevelProperty));
+					PropertyPath path = PropertyPath.from(topLevelProperty, returnedType.getDomainType());
+					selections.add(QueryUtils.toExpressionRecursively(root, path, true).alias(topLevelProperty));
+				}
 			}
 
 			Class<?> typeToRead = returnedType.getReturnedType();

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

@@ -39,6 +39,11 @@ import org.springframework.test.context.ContextConfiguration;
 @Disabled("hsqldb seems to hang on this test class without leaving a surefire report")
 class EclipseLinkNamespaceUserRepositoryTests extends NamespaceUserRepositoryTests {
 
+	@Disabled("EclipseLink does not support records, additionally, it does not support constructor creation using nested (join) properties")
+	@Override
+	@Test
+	public void findByFluentSpecificationWithDtoProjectionJoins() {}
+
 	/**
 	 * Ignored until https://bugs.eclipse.org/bugs/show_bug.cgi?id=422450 is resolved.
 	 */

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

@@ -2846,21 +2846,36 @@ class UserRepositoryTests {
 
 		flushTestUsers();
 
-		User prototype = new User();
-		prototype.setFirstname("v");
+		record MyProjection(String name, int age, boolean active) {
 
-		record MyProjection(String name) {
+		}
 
+		List<MyProjection> users = repository.findBy(userHasFirstnameLike("Oliver"), //
+				q -> q.project("firstname", "age", "active").as(MyProjection.class).all());
+
+		assertThat(users).hasSize(1).extracting(MyProjection::name).contains(firstUser.getFirstname());
+	}
+
+	@Test // GH-4172
+	void findByFluentSpecificationWithDtoProjectionJoins() {
+
+		flushTestUsers();
+		firstUser.setManager(secondUser);
+		em.persist(firstUser);
+		em.flush();
+
+		record MyProjection(String name, int age, boolean active, String managerName, int managerAge) {
 		}
 
-		List<MyProjection> users = repository.findBy(
-				of(prototype,
-						matching().withIgnorePaths("age", "createdAt", "active").withMatcher("firstname",
-								GenericPropertyMatcher::contains)), //
-				q -> q.project("firstname").as(MyProjection.class).all());
+		List<MyProjection> result = repository.findBy(userHasFirstnameLike("Oliver"), //
+				q -> q.project("firstname", "age", "active", "manager.firstname", "manager.age").as(MyProjection.class).all());
 
-		assertThat(users).extracting(MyProjection::name).containsExactlyInAnyOrder(firstUser.getFirstname(),
-				thirdUser.getFirstname(), fourthUser.getFirstname());
+		assertThat(result).hasSize(1);
+
+		MyProjection projection = result.get(0);
+		assertThat(projection.name()).isEqualTo(firstUser.getFirstname());
+		assertThat(projection.managerName()).isEqualTo(secondUser.getFirstname());
+		assertThat(projection.managerAge()).isEqualTo(secondUser.getAge());
 	}
 
 	@Test // GH-2274