GH-684 - Fix possible NPE in IdentityMap.

The identity map used the wrong map to look up the expected hash value when both a node and relationship with the same id have been loaded and a NPE happened when casting literal Null to long. This has been fixed by first selecting the correct hash.

The error first appeared in the performance optimizations in #576, #577 and #579.

core/src/main/java/org/neo4j/ogm/context/IdentityMap.java

@@ -90,17 +90,22 @@ void remember(Object object, Long entityId) {
      */
     boolean remembered(Object object, Long entityId) {
 
-        // Bail out early if the native id is null or neither the hashes of nodes nor relationships contain the entity id.
-        if (entityId == null || !(nodeHashes.containsKey(entityId) || relEntityHashes.containsKey(entityId))) {
+        // Bail out early if the native id is null...
+        if (entityId == null) {
             return false;
         }
 
         ClassInfo classInfo = metaData.classInfo(object);
         boolean isRelEntity = metaData.isRelationshipEntity(classInfo.name());
+        Map<Long, Long> hashes = isRelEntity ? relEntityHashes : nodeHashes;
 
-        long actual = hash(object, classInfo);
-        long expected = isRelEntity ? relEntityHashes.get(entityId) : nodeHashes.get(entityId);
+        // ... or a little later when the hashes in question doesnt contain the entities id
+        if (!hashes.containsKey(entityId)) {
+            return false;
+        }
 
+        long actual = hash(object, classInfo);
+        long expected = hashes.get(entityId);
         return actual == expected;
     }
 

neo4j-ogm-tests/neo4j-ogm-integration-tests/src/test/java/org/neo4j/ogm/context/IdentityMapTest.java

@@ -24,10 +24,12 @@
 import org.junit.Test;
 import org.neo4j.ogm.domain.education.School;
 import org.neo4j.ogm.domain.education.Teacher;
+import org.neo4j.ogm.domain.education.TeachesAt;
 import org.neo4j.ogm.metadata.MetaData;
 
 /**
  * @author Vince Bickers
+ * @author Michael J. Simons
  */
 public class IdentityMapTest {
 
@@ -70,4 +72,29 @@ public void testRelatedObjectChangeDoesNotAffectNodeMemoisation() {
 
         assertThat(mappingContext.isDirty(teacher)).isFalse();
     }
+
+    @Test // GH-684
+    public void testNodeAndRelationshipWithSameId() {
+
+        // Create a Node and set the Id.
+        Teacher mrsJones = new Teacher();
+        mrsJones.setId(1L);
+
+        // Remember the entity.
+        mappingContext.addNodeEntity(mrsJones);
+
+        // Create a Relationship with the same Id.
+        TeachesAt teachesAtRelationship = new TeachesAt();
+        teachesAtRelationship.setId(1L);
+
+        IdentityMap identityMap = new IdentityMap(metaData);
+        identityMap.remember(mrsJones, mrsJones.getId());
+
+        assertThat(identityMap.remembered(mrsJones, mrsJones.getId())).isTrue();
+        assertThat(identityMap.remembered(teachesAtRelationship, teachesAtRelationship.getId())).isFalse();
+
+        identityMap.remember(teachesAtRelationship, teachesAtRelationship.getId());
+
+        assertThat(identityMap.remembered(teachesAtRelationship, teachesAtRelationship.getId())).isTrue();
+    }
 }

neo4j-ogm-tests/neo4j-ogm-integration-tests/src/test/java/org/neo4j/ogm/domain/education/TeachesAt.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2002-2019 "Neo4j,"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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
+ *
+ *     http://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.neo4j.ogm.domain.education;
+
+import org.neo4j.ogm.annotation.Id;
+import org.neo4j.ogm.annotation.RelationshipEntity;
+
+/**
+ * @author Michael J. Simons
+ */
+@RelationshipEntity
+public class TeachesAt {
+
+    @Id
+    private Long id;
+
+    public long getId() { return id; }
+
+    public void setId(long id) { this.id = id; }
+}