GH-2349 - Fix NullPointerException when using known entities inside projections.

When a known entity is discovered in the PropertyFilterSupport, it can be used directly as the property type than is equal to a domain type (a well known entity).

Prior to that change, the discovered well known entity was used and it was asked for the the type of the property of the containing class again, which is wrong in most cases that don't have a property of the fitting type _and_ the same name again.

In addition, one other bug has been fixed: The `Neo4jTemplate` did not pass result type and domain type in the `saveAs` method to the `PropertyFilterSupport`, but only the result type, leading to the original fix to blow up.
Having fixed that bug, it became appearent that in the `PropertyFilterSupport` the overloads of `addPropertiesFrom` different order of `domainType` and `returnType`which then has been fixed as well.

This closes #2349.

Author: michael-simons

src/main/java/org/springframework/data/neo4j/core/Neo4jTemplate.java

@@ -332,7 +332,7 @@ public <T, R> R saveAs(T instance, Class<R> resultType) {
 		}
 
 		ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(resultType);
-		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, resultType,
+		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(instance.getClass(), resultType,
 				projectionFactory, neo4jMappingContext);
 
 		T savedInstance = saveImpl(instance, pps);
@@ -496,7 +496,7 @@ public <T, R> List<R> saveAllAs(Iterable<T> instances, Class<R> resultType) {
 
 		ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(resultType);
 
-		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, commonElementType,
+		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(commonElementType, resultType,
 				projectionFactory, neo4jMappingContext);
 
 		List<T> savedInstances = saveAllImpl(instances, new ArrayList<>(pps));
@@ -898,7 +898,7 @@ <T, R> List<R> doSave(Iterable<R> instances, Class<T> domainType) {
 
 		Class<?> resultType = TemplateSupport.findCommonElementType(instances);
 
-		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, domainType,
+		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(domainType, resultType,
 				projectionFactory, neo4jMappingContext);
 
 		List<R> results = new ArrayList<>();

src/main/java/org/springframework/data/neo4j/core/PropertyFilterSupport.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.neo4j.core;
 
+import org.apiguardian.api.API;
 import org.springframework.data.mapping.PropertyPath;
 import org.springframework.data.neo4j.core.mapping.Neo4jMappingContext;
 import org.springframework.data.neo4j.core.mapping.Neo4jPersistentEntity;
@@ -35,7 +36,8 @@
  * This class is responsible for creating a List of {@link PropertyPath} entries that contains all reachable
  * properties (w/o circles).
  */
-public class PropertyFilterSupport {
+@API(status = API.Status.INTERNAL, since = "6.1.3")
+public final class PropertyFilterSupport {
 
 	public static List<PropertyPath> getInputProperties(ResultProcessor resultProcessor, ProjectionFactory factory,
 														Neo4jMappingContext mappingContext) {
@@ -58,14 +60,14 @@ public static List<PropertyPath> getInputProperties(ResultProcessor resultProces
 		return filteredProperties;
 	}
 
-	public static List<PropertyPath> addPropertiesFrom(Class<?> returnType, Class<?> domainType,
+	static List<PropertyPath> addPropertiesFrom(Class<?> domainType, Class<?> returnType,
 													   ProjectionFactory projectionFactory,
 													   Neo4jMappingContext neo4jMappingContext) {
 
 		ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(returnType);
 		List<PropertyPath> propertyPaths = new ArrayList<>();
 		for (PropertyDescriptor inputProperty : projectionInformation.getInputProperties()) {
-			addPropertiesFrom(returnType, domainType, projectionFactory, propertyPaths, inputProperty.getName(), neo4jMappingContext);
+			addPropertiesFrom(domainType, returnType, projectionFactory, propertyPaths, inputProperty.getName(), neo4jMappingContext);
 		}
 		return propertyPaths;
 	}
@@ -97,8 +99,8 @@ private static void addPropertiesFrom(Class<?> domainType, Class<?> returnedType
 			if (propertyType.equals(domainType)) {
 				return;
 			}
-			processEntity(domainType, filteredProperties, inputProperty, mappingContext);
 
+			addPropertiesFromEntity(filteredProperties, propertyPath, propertyType, mappingContext, new HashSet<>());
 		} else {
 			ProjectionInformation nestedProjectionInformation = factory.getProjectionInformation(propertyType);
 			filteredProperties.add(propertyPath);

src/main/java/org/springframework/data/neo4j/core/ReactiveNeo4jTemplate.java

@@ -316,7 +316,7 @@ public <T, R> Mono<R> saveAs(T instance, Class<R> resultType) {
 		}
 
 		ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(resultType);
-		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, instance.getClass(),
+		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(instance.getClass(), resultType,
 				projectionFactory, neo4jMappingContext);
 
 		Mono<T> savingPublisher = saveImpl(instance, pps);
@@ -342,7 +342,7 @@ <T, R> Flux<R> doSave(Iterable<R> instances, Class<T> domainType) {
 
 		Class<?> resultType = TemplateSupport.findCommonElementType(instances);
 
-		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, domainType,
+		Collection<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(domainType, resultType,
 				projectionFactory, neo4jMappingContext);
 
 		return Flux.fromIterable(instances)
@@ -443,7 +443,7 @@ public <T, R> Flux<R> saveAllAs(Iterable<T> instances, Class<R> resultType) {
 		}
 
 		ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(resultType);
-		List<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(resultType, commonElementType,
+		List<PropertyPath> pps = PropertyFilterSupport.addPropertiesFrom(commonElementType, resultType,
 				projectionFactory, neo4jMappingContext);
 
 		Flux<T> savedInstances = saveAllImpl(instances, pps);

src/test/java/org/springframework/data/neo4j/integration/imperative/ProjectionIT.java

@@ -19,6 +19,7 @@
 
 import java.util.AbstractMap;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -44,8 +45,12 @@
 import org.springframework.data.domain.Sort;
 import org.springframework.data.neo4j.config.AbstractNeo4jConfig;
 import org.springframework.data.neo4j.core.DatabaseSelectionProvider;
+import org.springframework.data.neo4j.core.Neo4jTemplate;
 import org.springframework.data.neo4j.core.transaction.Neo4jBookmarkManager;
 import org.springframework.data.neo4j.core.transaction.Neo4jTransactionManager;
+import org.springframework.data.neo4j.integration.shared.common.DepartmentEntity;
+import org.springframework.data.neo4j.integration.shared.common.PersonDepartmentQueryResult;
+import org.springframework.data.neo4j.integration.shared.common.PersonEntity;
 import org.springframework.data.neo4j.integration.shared.common.NamesOnly;
 import org.springframework.data.neo4j.integration.shared.common.NamesOnlyDto;
 import org.springframework.data.neo4j.integration.shared.common.NamesWithSpELCity;
@@ -98,6 +103,7 @@ void setup() {
 		Transaction transaction = session.beginTransaction();) {
 
 			transaction.run("MATCH (n) detach delete n");
+			transaction.run("CREATE (p:PersonEntity {id: 'p1', email: '[email protected]'}) -[:MEMBER_OF]->(department:DepartmentEntity {id: 'd1', name: 'Dep1'}) RETURN p");
 
 			for (Map.Entry<String, String> person : new Map.Entry[] {
 					new AbstractMap.SimpleEntry(FIRST_NAME, LAST_NAME),
@@ -337,6 +343,35 @@ void findCypherDSLClosedProjection(@Autowired ProjectionPersonRepository reposit
 		assertThat(personSummary.get().getLastName()).isEqualTo(LAST_NAME);
 	}
 
+	@Test // GH-2349
+	void projectionsContainingKnownEntitiesShouldWorkFromRepository(@Autowired PersonRepository personRepository) {
+
+		List<PersonDepartmentQueryResult> results = personRepository.findPersonWithDepartment();
+		assertThat(results)
+				.hasSize(1)
+				.first()
+				.satisfies(personAndDepartment -> projectedEntities(personAndDepartment));
+	}
+
+	@Test // GH-2349
+	void projectionsContainingKnownEntitiesShouldWorkFromTemplate(@Autowired Neo4jTemplate template) {
+
+		List<PersonDepartmentQueryResult> results = template.find(PersonEntity.class).as(PersonDepartmentQueryResult.class)
+				.matching("MATCH (person:PersonEntity)-[:MEMBER_OF]->(department:DepartmentEntity) RETURN person, department")
+				.all();
+		assertThat(results)
+				.hasSize(1)
+				.first()
+				.satisfies(personAndDepartment -> projectedEntities(personAndDepartment));
+	}
+
+	private static void projectedEntities(PersonDepartmentQueryResult personAndDepartment) {
+		assertThat(personAndDepartment.getPerson()).extracting(PersonEntity::getId).isEqualTo("p1");
+		assertThat(personAndDepartment.getPerson()).extracting(PersonEntity::getEmail).isEqualTo("[email protected]");
+		assertThat(personAndDepartment.getDepartment()).extracting(DepartmentEntity::getId).isEqualTo("d1");
+		assertThat(personAndDepartment.getDepartment()).extracting(DepartmentEntity::getName).isEqualTo("Dep1");
+	}
+
 	private static Statement whoHasFirstName(String firstName) {
 		Node p = Cypher.node("Person").named("p");
 		return Cypher.match(p)
@@ -438,6 +473,11 @@ interface Subprojection2 {
 		}
 	}
 
+	interface PersonRepository extends Neo4jRepository<PersonEntity, String> {
+		@Query("MATCH (person:PersonEntity)-[:MEMBER_OF]->(department:DepartmentEntity) RETURN person, department")
+		List<PersonDepartmentQueryResult> findPersonWithDepartment();
+	}
+
 	@Configuration
 	@EnableNeo4jRepositories(considerNestedRepositories = true)
 	@EnableTransactionManagement
@@ -453,6 +493,11 @@ public BookmarkCapture bookmarkCapture() {
 			return new BookmarkCapture();
 		}
 
+		@Override
+		protected Collection<String> getMappingBasePackages() {
+			return Collections.singletonList(DepartmentEntity.class.getPackage().getName());
+		}
+
 		@Override
 		public PlatformTransactionManager transactionManager(Driver driver, DatabaseSelectionProvider databaseNameProvider) {
 

src/test/java/org/springframework/data/neo4j/integration/shared/common/DepartmentEntity.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2011-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.neo4j.integration.shared.common;
+
+import org.springframework.data.neo4j.core.schema.Id;
+import org.springframework.data.neo4j.core.schema.Node;
+
+/**
+ * @∆author Michael J. Simons
+ */
+@Node
+public class DepartmentEntity {
+
+	@Id
+	private final String id;
+	private final String name;
+
+	public DepartmentEntity(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return this.id;
+	}
+
+	public String getName() {
+		return this.name;
+	}
+}

src/test/java/org/springframework/data/neo4j/integration/shared/common/PersonDepartmentQueryResult.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2011-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.neo4j.integration.shared.common;
+
+/**
+ * @author Michael J. Simons
+ */
+public class PersonDepartmentQueryResult {
+
+	private final PersonEntity person;
+	private final DepartmentEntity department;
+
+	public PersonDepartmentQueryResult(PersonEntity person, DepartmentEntity department) {
+		this.person = person;
+		this.department = department;
+	}
+
+	public PersonEntity getPerson() {
+		return this.person;
+	}
+
+	public DepartmentEntity getDepartment() {
+		return this.department;
+	}
+}

src/test/java/org/springframework/data/neo4j/integration/shared/common/PersonEntity.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2011-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.neo4j.integration.shared.common;
+
+import org.springframework.data.neo4j.core.schema.Id;
+import org.springframework.data.neo4j.core.schema.Node;
+
+/**
+ * @author Michael J. Simons
+ */
+@Node
+public class PersonEntity {
+	@Id
+	private final String id;
+	private final String email;
+
+	public PersonEntity(String id, String email) {
+		this.id = id;
+		this.email = email;
+	}
+
+	public String getId() {
+		return this.id;
+	}
+
+	public String getEmail() {
+		return this.email;
+	}
+}