INT-3910: MessageProducerSupport.outputChannelName

JIRA: https://jira.spring.io/browse/INT-3910

- Support channel name on `MessageProducerSupport`.
- Defer validation until the endpoint is `start()`ed.

spring-integration-core/src/main/java/org/springframework/integration/endpoint/MessageProducerSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -25,6 +25,7 @@ import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessagingException;
 import org.springframework.messaging.support.ErrorMessage;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * A support class for producer endpoints that provides a setter for the
@@ -36,14 +37,16 @@ import org.springframework.util.Assert;
  */
 public abstract class MessageProducerSupport extends AbstractEndpoint implements MessageProducer, TrackableComponent {
 
+	private final MessagingTemplate messagingTemplate = new MessagingTemplate();
+
 	private volatile MessageChannel outputChannel;
 
+	private volatile String outputChannelName;
+
 	private volatile MessageChannel errorChannel;
 
 	private volatile boolean shouldTrack = false;
 
-	private final MessagingTemplate messagingTemplate = new MessagingTemplate();
-
 	protected MessageProducerSupport() {
 		this.setPhase(Integer.MAX_VALUE / 2);
 	}
@@ -53,6 +56,17 @@ public abstract class MessageProducerSupport extends AbstractEndpoint implements
 		this.outputChannel = outputChannel;
 	}
 
+	/**
+	 * Set the output channel name; overrides
+	 * {@link #setOutputChannel(MessageChannel) outputChannel} if provided.
+	 * @param outputChannelName the channel name.
+	 * @since 4.3
+	 */
+	public void setOutputChannelName(String outputChannelName) {
+		Assert.hasText(outputChannelName, "'outputChannelName' must not be null or empty");
+		this.outputChannelName = outputChannelName;
+	}
+
 	public void setErrorChannel(MessageChannel errorChannel) {
 		this.errorChannel = errorChannel;
 	}
@@ -72,7 +86,6 @@ public abstract class MessageProducerSupport extends AbstractEndpoint implements
 
 	@Override
 	protected void onInit() {
-		Assert.notNull(this.outputChannel, "outputChannel is required");
 		if (this.getBeanFactory() != null) {
 			this.messagingTemplate.setBeanFactory(this.getBeanFactory());
 		}
@@ -80,10 +93,15 @@ public abstract class MessageProducerSupport extends AbstractEndpoint implements
 
 	/**
 	 * Takes no action by default. Subclasses may override this if they
-	 * need lifecycle-managed behavior.
+	 * need lifecycle-managed behavior. Protected by 'lifecycleLock'.
 	 */
 	@Override
 	protected void doStart() {
+		Assert.state(this.outputChannel != null || StringUtils.hasText(this.outputChannelName),
+				"'outputChannel' or 'outputChannelName' is required");
+		if (this.outputChannelName != null) {
+			this.outputChannel = getChannelResolver().resolveDestination(this.outputChannelName);
+		}
 	}
 
 	/**

spring-integration-core/src/test/java/org/springframework/integration/endpoint/MessageProducerSupportTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -18,6 +18,7 @@ package org.springframework.integration.endpoint;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Mockito.mock;
 
@@ -25,11 +26,13 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.Test;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.integration.channel.DirectChannel;
 import org.springframework.integration.channel.PublishSubscribeChannel;
 import org.springframework.integration.handler.ServiceActivatingHandler;
 import org.springframework.integration.test.util.TestUtils;
+import org.springframework.integration.test.util.TestUtils.TestApplicationContext;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageDeliveryException;
 import org.springframework.messaging.MessageHandler;
@@ -119,6 +122,20 @@ public class MessageProducerSupportTests {
 		assertEquals(message, exception.getFailedMessage());
 	}
 
+	@Test
+	public void testWithChannelName() {
+		DirectChannel outChannel = new DirectChannel();
+		MessageProducerSupport mps = new MessageProducerSupport() {};
+		mps.setOutputChannelName("foo");
+		TestApplicationContext testApplicationContext = TestUtils.createTestApplicationContext();
+		testApplicationContext.registerBean("foo", outChannel);
+		testApplicationContext.refresh();
+		mps.setBeanFactory(testApplicationContext);
+		mps.afterPropertiesSet();
+		mps.start();
+		assertSame(outChannel, TestUtils.getPropertyValue(mps, "outputChannel"));
+	}
+
 	@Test
 	public void customDoStop() {
 		final CustomEndpoint endpoint = new CustomEndpoint();