DATAREST-221 - Further refinements in Projector.

Prevent NullPointerException in case we don't find a requested projection. We simply return the source object if so. Added unit tests to make sure we don't introduce a regression.

Removed NoOpProjector from production code as it is only needed in test cases anyway.

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/support/PersistentEntityProjector.java

@@ -61,6 +61,6 @@ public class PersistentEntityProjector implements Projector {
 		}
 
 		Class<?> projectionType = projectionDefinitions.getProjectionType(source.getClass(), projection);
-		return factory.createProjection(source, projectionType);
+		return projectionType == null ? source : factory.createProjection(source, projectionType);
 	}
 }

spring-data-rest-webmvc/src/main/java/org/springframework/data/rest/webmvc/support/Projector.java

@@ -16,23 +16,18 @@
 package org.springframework.data.rest.webmvc.support;
 
 /**
+ * Interface for a component being able to create projections for objects.
+ * 
  * @author Oliver Gierke
  */
 public interface Projector {
 
+	/**
+	 * Returns the projection object for the given source. This may result in the same object being returned or a
+	 * completely different acting as projection for the source.
+	 * 
+	 * @param source must not be {@literal null}.
+	 * @return
+	 */
 	public Object project(Object source);
-
-	enum NoOpProjector implements Projector {
-
-		INSTANCE;
-
-		/* 
-		 * (non-Javadoc)
-		 * @see org.springframework.data.rest.webmvc.support.Projector#project(java.lang.Object)
-		 */
-		@Override
-		public Object project(Object source) {
-			return source;
-		}
-	}
 }

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/AbstractControllerIntegrationTests.java

@@ -53,7 +53,12 @@ public abstract class AbstractControllerIntegrationTests {
 
 		@Bean
 		public PersistentEntityResourceAssembler persistentEntityResourceAssembler() {
-			return new PersistentEntityResourceAssembler(repositories(), entityLinks(), Projector.NoOpProjector.INSTANCE);
+			return new PersistentEntityResourceAssembler(repositories(), entityLinks(), new Projector() {
+				@Override
+				public Object project(Object source) {
+					return source;
+				}
+			});
 		}
 	}
 

spring-data-rest-webmvc/src/test/java/org/springframework/data/rest/webmvc/support/PersistentEntityProjectorUnitTests.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2014 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
+ *
+ *      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.springframework.data.rest.webmvc.support;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.springframework.data.rest.core.config.ProjectionDefinitionConfiguration;
+import org.springframework.data.rest.core.projection.ProjectionFactory;
+
+/**
+ * Unit tests for {@link PersistentEntityProjector}.
+ * 
+ * @author Oliver Gierke
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class PersistentEntityProjectorUnitTests {
+
+	@Mock ProjectionFactory factory;
+	ProjectionDefinitionConfiguration configuration;
+
+	@Before
+	public void setUp() {
+		configuration = new ProjectionDefinitionConfiguration();
+	}
+
+	/**
+	 * @see DATAREST-221
+	 */
+	@Test
+	public void returnsObjectAsIfNoProjectionTypeFound() {
+
+		Projector projector = new PersistentEntityProjector(configuration, factory, "sample");
+
+		Object object = new Object();
+		assertThat(projector.project(object), is(object));
+	}
+
+	/**
+	 * @see DATAREST-221
+	 */
+	@Test
+	public void invokesProjectionFactoryIfProjectionFound() {
+
+		configuration.addProjection(Sample.class, Object.class);
+
+		Projector projector = new PersistentEntityProjector(configuration, factory, "sample");
+		Object source = new Object();
+		projector.project(source);
+
+		verify(factory, times(1)).createProjection(source, Sample.class);
+	}
+
+	interface Sample {
+
+	}
+}