fix: Handle null properties.

When using stored procedures the transport of actual `null` properties in entities is possible and leads to a NPE. This changes checks for `NO_VALUE` respectively `NullValue` and filters literal `null` properties afterwards.

Closes #909.

api/src/main/java/org/neo4j/ogm/result/adapter/BaseAdapter.java

@@ -32,6 +32,7 @@ public class BaseAdapter {
 
     public Map<String, Object> convertArrayPropertiesToCollection(Map<String, Object> properties) {
         return properties.entrySet().stream()
+            .filter(e -> e.getValue() != null)
             .collect(toMap(Map.Entry::getKey, BaseAdapter::convertOrReturnSelf));
     }
 

bolt-driver/src/main/java/org/neo4j/ogm/drivers/bolt/driver/BoltEntityAdapter.java

@@ -24,6 +24,7 @@
 
 import org.neo4j.driver.internal.value.ListValue;
 import org.neo4j.driver.Value;
+import org.neo4j.driver.internal.value.NullValue;
 import org.neo4j.driver.types.Entity;
 import org.neo4j.driver.types.Node;
 import org.neo4j.driver.types.Path;
@@ -111,7 +112,7 @@ public List<Object> relsInPath(Object pathValue) {
 
     private Object toMapped(Value value) {
 
-        if (value == null) {
+        if (value == null || value instanceof NullValue) {
             return null;
         }
 

embedded-driver/src/main/java/org/neo4j/ogm/drivers/embedded/driver/EmbeddedEntityAdapter.java

@@ -31,6 +31,7 @@
 import org.neo4j.graphdb.Entity;
 import org.neo4j.graphdb.Relationship;
 import org.neo4j.ogm.driver.TypeSystem;
+import org.neo4j.values.storable.Values;
 
 /**
  * Helper methods for embedded graph entities
@@ -116,7 +117,7 @@ public Map<String, Object> getAllProperties(Entity propertyContainer) {
 
     private Object toMapped(Object value) {
 
-        if (value == null) {
+        if (value == null || Values.NO_VALUE == value) {
             return null;
         }
 

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

@@ -33,6 +33,7 @@
 
 import org.assertj.core.api.Condition;
 import org.junit.BeforeClass;
+import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.neo4j.ogm.domain.cineasts.minimum.Actor;
@@ -359,6 +360,18 @@ public void shouldWorkWithCustomConvertersOnListProperty() {
             .containsExactlyInAnyOrder("foo", "bar");
     }
 
+    @Test // GH-909
+    @Ignore("This test requires APOC on the server, as there is no other way to create literal null properties on entities.")
+    public void shouldDealWithArtificalNullValues() {
+        SingleUseEntityMapper entityMapper =
+            new SingleUseEntityMapper(sessionFactory.metaData(),
+                new ReflectionEntityInstantiator(sessionFactory.metaData()));
+        Movie movie = sessionFactory.openSession()
+            .queryForObject(Movie.class, "return apoc.create.vNode(['Movie'],{name: null, foo: null})",
+                Collections.emptyMap());
+        assertThat(movie.getName()).isNull();
+    }
+
     @Test // GH-718
     public void queryResultShouldHandleNodeAndRelationshipEntities() {
 

neo4j-ogm-tests/neo4j-ogm-integration-tests/src/test/java/org/neo4j/ogm/domain/cineasts/minimum/Movie.java

@@ -32,4 +32,8 @@ public Movie() {
     public Movie(String name) {
         this.name = name;
     }
+
+    public String getName() {
+        return name;
+    }
 }