INT-4085: Access ARPMH from RequestHandlerAdvice

JIRA: https://jira.spring.io/browse/INT-4085

Polishing - PR Comments

spring-integration-core/src/main/java/org/springframework/integration/handler/AbstractReplyProducingMessageHandler.java

@@ -138,6 +138,18 @@ public abstract class AbstractReplyProducingMessageHandler extends AbstractMessa
 	protected abstract Object handleRequestMessage(Message<?> requestMessage);
 
 
+	/**
+	 * An implementation of this interface is used to wrap the
+	 * {@link AbstractReplyProducingMessageHandler#handleRequestMessage(Message)}
+	 * method. Also allows access to the underlying
+	 * {@link AbstractReplyProducingMessageHandler} to obtain properties.
+	 *
+	 * @author Gary Russell
+	 * @since 2.2
+	 *
+	 * @see #getAdvisedHandler()
+	 *
+	 */
 	public interface RequestHandler {
 
 		Object handleRequestMessage(Message<?> requestMessage);
@@ -145,6 +157,18 @@ public abstract class AbstractReplyProducingMessageHandler extends AbstractMessa
 		@Override
 		String toString();
 
+		/**
+		 * Utility method, intended for use in message handler advice classes to get
+		 * information about the advised object. For example:
+		 * <p>
+		 * {@code ((AbstractReplyProducingMessageHandler.RequestHandler)
+		 * invocation.getThis()).getAdvisedHandler().getComponentName()}
+		 * @return the outer class instance.
+		 *
+		 * @since 4.3.2
+		 */
+		AbstractReplyProducingMessageHandler getAdvisedHandler();
+
 	}
 
 	private class AdvisedRequestHandler implements RequestHandler {
@@ -159,6 +183,11 @@ public abstract class AbstractReplyProducingMessageHandler extends AbstractMessa
 			return AbstractReplyProducingMessageHandler.this.toString();
 		}
 
+		@Override
+		public AbstractReplyProducingMessageHandler getAdvisedHandler() {
+			return AbstractReplyProducingMessageHandler.this;
+		}
+
 	}
 
 }

spring-integration-core/src/test/java/org/springframework/integration/handler/advice/AdvisedMessageHandlerTests.java

@@ -132,6 +132,8 @@ public class AdvisedMessageHandlerTests {
 				return "baz";
 			}
 		};
+		String componentName = "testComponentName";
+		handler.setComponentName(componentName);
 		QueueChannel replies = new QueueChannel();
 		handler.setOutputChannel(replies);
 		Message<String> message = new GenericMessage<String>("Hello, world!");
@@ -153,6 +155,17 @@ public class AdvisedMessageHandlerTests {
 
 		List<Advice> adviceChain = new ArrayList<Advice>();
 		adviceChain.add(advice);
+		final AtomicReference<String> compName = new AtomicReference<String>();
+		adviceChain.add(new AbstractRequestHandlerAdvice() {
+
+			@Override
+			protected Object doInvoke(ExecutionCallback callback, Object target, Message<?> message) throws Exception {
+				compName.set(((AbstractReplyProducingMessageHandler.RequestHandler) target).getAdvisedHandler()
+						.getComponentName());
+				return callback.execute();
+			}
+
+		});
 		handler.setAdviceChain(adviceChain);
 		handler.setBeanFactory(mock(BeanFactory.class));
 		handler.afterPropertiesSet();
@@ -163,6 +176,8 @@ public class AdvisedMessageHandlerTests {
 		assertNotNull(reply);
 		assertEquals("baz", reply.getPayload());
 
+		assertEquals(componentName, compName.get());
+
 		Message<?> success = successChannel.receive(1000);
 		assertNotNull(success);
 		assertEquals("Hello, world!", ((AdviceMessage<?>) success).getInputMessage().getPayload());

src/reference/asciidoc/handler-advice.adoc

@@ -395,7 +395,7 @@ If you wish to suppress throwing the exception, set the `trapException` property
 ==== Custom Advice Classes
 
 In addition to the provided Advice classes above, you can implement your own Advice classes.
-While you can provide any implementation of `org.aopalliance.aop.Advice`, it is generally recommended that you subclass `o.s.i.handler.advice.AbstractRequestHandlerAdvice`.
+While you can provide any implementation of `org.aopalliance.aop.Advice` (usually `org.aopalliance.intercept.MethodInterceptor`), it is generally recommended that you subclass `o.s.i.handler.advice.AbstractRequestHandlerAdvice`.
 This has the benefit of avoiding writing low-level _Aspect Oriented Programming_ code as well as providing a starting point that is specifically tailored for use in this environment.
 
 Subclasses need to implement the `doInvoke()`` method:
@@ -530,6 +530,42 @@ You may want to place the retry advice advice first, followed by the transaction
 Then, each retry will be performed in a new transaction.
 On the other hand, if you want all the attempts, and any recovery operations (in the retry `RecoveryCallback`), to be scoped within the transaction, you would put the transaction advice first.
 
+[[advised-handler-properties]]
+==== Advised Handler Properties
+
+Sometimes, it is useful to access handler properties from within the advice.
+For example, most handlers implement `NamedComponent` and you can access the component name.
+
+The target object can be accessed via the `target` argument when subclassing `AbstractRequestHandlerAdvice` or
+`invocation.getThis()` when implementing `org.aopalliance.intercept.MethodInterceptor`.
+
+When the entire handler is advised (such as when the handler does not produce replies, or the advice implements `HandleMessageAdvice`), you can simply cast the target object to the desired implemented interface, such as `NamedComponent`.
+
+[source, java]
+----
+String componentName = ((NamedComponent) target).getComponentName();
+----
+
+or
+
+[source, java]
+----
+String componentName = ((NamedComponent) invocation.getThis()).getComponentName();
+----
+
+when implementing `MethodInterceptor` directly.
+
+When only the `handleRequestMessage()` method is advised (in a reply-producing handler), you need to access the
+full handler, which is an `AbstractReplyProducingMessageHandler`...
+
+[source, java]
+----
+AbstractReplyProducingMessageHandler handler =
+    ((AbstractReplyProducingMessageHandler.RequestHandler) target).getAdvisedHandler();
+
+String componentName = handler.getComponentName();
+----
+
 [[idempotent-receiver]]
 ==== Idempotent Receiver Enterprise Integration Pattern