Issue #559: Fixed static factory method of `RetrieveFeatureDesiredPro…

…pertiesResponse`.

When passing null for a `JsonObject` it threw a NPE. However, the parameter is annotated with `@Nullable`.

Signed-off-by: Juergen Fickel <juergen.fickel@bosch.io>

things/model/src/main/java/org/eclipse/ditto/things/model/signals/commands/query/RetrieveFeatureDesiredPropertiesResponse.java

@@ -103,15 +103,19 @@ public static RetrieveFeatureDesiredPropertiesResponse of(final ThingId thingId,
      * @param jsonObject the retrieved desired properties JSON.
      * @param dittoHeaders the headers of the preceding command.
      * @return the response.
-     * @throws NullPointerException if any argument is {@code null}.
+     * @throws NullPointerException if any argument but {@code jsonObject} is {@code null}.
      */
     public static RetrieveFeatureDesiredPropertiesResponse of(final ThingId thingId,
             final CharSequence featureId,
             @Nullable final JsonObject jsonObject,
             final DittoHeaders dittoHeaders) {
 
-        checkNotNull(jsonObject, "jsonObject");
-        final FeatureProperties desiredProperties = ThingsModelFactory.newFeatureProperties(jsonObject);
+        final FeatureProperties desiredProperties;
+        if (null == jsonObject) {
+            desiredProperties = ThingsModelFactory.newFeatureProperties(JsonFactory.nullObject());
+        } else {
+            desiredProperties = ThingsModelFactory.newFeatureProperties(jsonObject);
+        }
 
         return of(thingId, featureId, desiredProperties, dittoHeaders);
     }

things/model/src/test/java/org/eclipse/ditto/things/model/signals/commands/query/RetrieveFeatureDesiredPropertiesResponseTest.java

@@ -17,24 +17,30 @@
 import static org.mutabilitydetector.unittesting.MutabilityAssert.assertInstancesOf;
 import static org.mutabilitydetector.unittesting.MutabilityMatchers.areImmutable;
 
-import org.assertj.core.api.Assertions;
-import org.eclipse.ditto.json.JsonFactory;
-import org.eclipse.ditto.json.JsonObject;
 import org.eclipse.ditto.base.model.common.HttpStatus;
+import org.eclipse.ditto.base.model.headers.DittoHeaders;
 import org.eclipse.ditto.base.model.json.FieldType;
 import org.eclipse.ditto.base.model.json.JsonSchemaVersion;
+import org.eclipse.ditto.json.JsonFactory;
+import org.eclipse.ditto.json.JsonObject;
 import org.eclipse.ditto.things.model.FeatureProperties;
 import org.eclipse.ditto.things.model.ThingId;
+import org.eclipse.ditto.things.model.ThingsModelFactory;
 import org.eclipse.ditto.things.model.signals.commands.TestConstants;
 import org.eclipse.ditto.things.model.signals.commands.ThingCommandResponse;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TestName;
 
 import nl.jqno.equalsverifier.EqualsVerifier;
 
 /**
  * Unit test for {@link RetrieveFeatureDesiredPropertiesResponse}.
  */
-public class RetrieveFeatureDesiredPropertiesResponseTest {
+public final class RetrieveFeatureDesiredPropertiesResponseTest {
+
+    @Rule
+    public final TestName testName = new TestName();
 
     private static final JsonSchemaVersion KNOWN_SCHEMA_VERSION = JsonSchemaVersion.V_2;
 
@@ -47,46 +53,57 @@ public class RetrieveFeatureDesiredPropertiesResponseTest {
                     TestConstants.Feature.HOVER_BOARD_DESIRED_PROPERTIES.toJson(KNOWN_SCHEMA_VERSION))
             .build();
 
-
     @Test
     public void assertImmutability() {
         assertInstancesOf(RetrieveFeatureDesiredPropertiesResponse.class, areImmutable(),
                 provided(FeatureProperties.class, ThingId.class).isAlsoImmutable());
     }
 
-
     @Test
     public void testHashCodeAndEquals() {
         EqualsVerifier.forClass(RetrieveFeatureDesiredPropertiesResponse.class)
                 .withRedefinedSuperclass()
                 .verify();
     }
 
-
     @Test(expected = NullPointerException.class)
     public void tryToCreateInstanceWithNullFeatureDesiredProperties() {
-        RetrieveFeatureDesiredPropertiesResponse.of(TestConstants.Thing.THING_ID, TestConstants.Feature.HOVER_BOARD_ID,
+        RetrieveFeatureDesiredPropertiesResponse.of(TestConstants.Thing.THING_ID,
+                TestConstants.Feature.HOVER_BOARD_ID,
                 null,
                 TestConstants.EMPTY_DITTO_HEADERS);
     }
 
-
     @Test
-    public void toJsonReturnsExpected() {
+    public void getInstanceWithNullFeaturePropertiesJsonObject() {
+        final DittoHeaders dittoHeaders = DittoHeaders.newBuilder().correlationId(testName.getMethodName()).build();
         final RetrieveFeatureDesiredPropertiesResponse underTest =
                 RetrieveFeatureDesiredPropertiesResponse.of(TestConstants.Thing.THING_ID,
                         TestConstants.Feature.HOVER_BOARD_ID,
-                        TestConstants.Feature.HOVER_BOARD_DESIRED_PROPERTIES, TestConstants.EMPTY_DITTO_HEADERS);
-        final String actualJsonString = underTest.toJson(FieldType.regularOrSpecial()).toString();
+                        (JsonObject) null,
+                        dittoHeaders);
 
-        Assertions.assertThat(actualJsonString).isEqualTo(KNOWN_JSON.toString());
+        assertThat(underTest.getDesiredProperties()).isEqualTo(ThingsModelFactory.emptyFeatureProperties());
     }
 
+    @Test
+    public void toJsonReturnsExpected() {
+        final RetrieveFeatureDesiredPropertiesResponse underTest = RetrieveFeatureDesiredPropertiesResponse.of(
+                TestConstants.Thing.THING_ID,
+                TestConstants.Feature.HOVER_BOARD_ID,
+                TestConstants.Feature.HOVER_BOARD_DESIRED_PROPERTIES,
+                TestConstants.EMPTY_DITTO_HEADERS
+        );
+        final String actualJsonString = underTest.toJson(FieldType.regularOrSpecial()).toString();
+
+        assertThat(actualJsonString).isEqualTo(KNOWN_JSON.toString());
+    }
 
     @Test
     public void createInstanceFromValidJson() {
         final RetrieveFeatureDesiredPropertiesResponse underTest =
-                RetrieveFeatureDesiredPropertiesResponse.fromJson(KNOWN_JSON.toString(), TestConstants.EMPTY_DITTO_HEADERS);
+                RetrieveFeatureDesiredPropertiesResponse.fromJson(KNOWN_JSON.toString(),
+                        TestConstants.EMPTY_DITTO_HEADERS);
 
         assertThat(underTest).isNotNull();
         assertThat(underTest.getDesiredProperties()).isEqualTo(TestConstants.Feature.HOVER_BOARD_DESIRED_PROPERTIES);