DATACMNS-1121 - ProxyProjectionFactory now returns instance as is if it implements the target.

If you previously asked ProxyProjectionFactory for a proxy of an interface which the target instance already implements, it created a proxy although it could've returned the instance as is. It's now actually doing that avoiding superfluous proxy creation.

src/main/java/org/springframework/data/projection/ProxyProjectionFactory.java

@@ -109,8 +109,8 @@ class ProxyProjectionFactory implements ProjectionFactory, ResourceLoaderAware,
 		Assert.notNull(projectionType, "Projection type must not be null!");
 		Assert.isTrue(projectionType.isInterface(), "Projection type must be an interface!");
 
-		if (source == null) {
-			return null;
+		if (source == null || projectionType.isInstance(source)) {
+			return (T) source;
 		}
 
 		ProxyFactory factory = new ProxyFactory();

src/test/java/org/springframework/data/projection/ProxyProjectionFactoryUnitTests.java

@@ -212,7 +212,17 @@ public class ProxyProjectionFactoryUnitTests {
 		assertThat(data.get("key"), is(nullValue()));
 	}
 
-	static class Customer {
+	@Test // DATACMNS-1121
+	public void doesNotCreateWrappingProxyIfTargetImplementsProjectionInterface() {
+
+		Customer customer = new Customer();
+
+		assertThat(factory.createProjection(Contact.class, customer) == customer, is(true));
+	}
+
+	interface Contact {}
+
+	static class Customer implements Contact {
 
 		public Long id;
 		public String firstname, lastname;