INT-1814 added INFO message when DirectChannel has more then one subscriber

spring-integration-core/src/main/java/org/springframework/integration/channel/AbstractMessageChannel.java

@@ -46,7 +46,7 @@ import org.springframework.util.StringUtils;
  */
 public abstract class AbstractMessageChannel extends IntegrationObjectSupport implements MessageChannel, TrackableComponent {
 
-	private final Log logger = LogFactory.getLog(this.getClass());
+	protected final Log logger = LogFactory.getLog(this.getClass());
 
 	private volatile boolean shouldTrack = false;
 

spring-integration-core/src/main/java/org/springframework/integration/channel/DirectChannel.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.channel;
 
+import org.springframework.integration.core.MessageHandler;
 import org.springframework.integration.dispatcher.LoadBalancingStrategy;
 import org.springframework.integration.dispatcher.RoundRobinLoadBalancingStrategy;
 import org.springframework.integration.dispatcher.UnicastingDispatcher;
@@ -33,6 +34,14 @@ public class DirectChannel extends AbstractSubscribableChannel {
 
 	private final UnicastingDispatcher dispatcher = new UnicastingDispatcher();
 
+	public boolean subscribe(MessageHandler handler) {
+		
+		if (this.getDispatcher().size() > 0){
+			this.logger.info("DirectChannel has more then 1 subscriber. " +
+					"Incoming messages will be dispatched between all subscribers following the load-balancing strategy.");
+		}
+		return super.subscribe(handler);
+	}
 
 	/**
 	 * Create a channel with default {@link RoundRobinLoadBalancingStrategy}

spring-integration-core/src/main/java/org/springframework/integration/dispatcher/AbstractDispatcher.java

@@ -77,4 +77,7 @@ public abstract class AbstractDispatcher implements MessageDispatcher {
 		return this.getClass().getSimpleName() + " with handlers: " + this.handlers.toString();
 	}
 
+	public int size(){
+		return this.handlers.toArray().length;
+	}
 }

spring-integration-core/src/test/java/org/springframework/integration/channel/DirectChannelTests.java

@@ -18,11 +18,17 @@ package org.springframework.integration.channel;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
 
+import java.lang.reflect.Field;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 
+import org.apache.commons.logging.Log;
 import org.junit.Test;
+import org.mockito.Mockito;
 
 import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.integration.Message;
@@ -30,6 +36,9 @@ import org.springframework.integration.core.MessageHandler;
 import org.springframework.integration.dispatcher.RoundRobinLoadBalancingStrategy;
 import org.springframework.integration.dispatcher.UnicastingDispatcher;
 import org.springframework.integration.message.GenericMessage;
+import org.springframework.integration.test.util.TestUtils;
+import org.springframework.util.ReflectionUtils;
+import org.springframework.util.ReflectionUtils.FieldCallback;
 
 /**
  * @author Mark Fisher
@@ -51,6 +60,26 @@ public class DirectChannelTests {
 		Object loadBalancingStrategy = dispatcherAccessor.getPropertyValue("loadBalancingStrategy");
 		assertTrue(loadBalancingStrategy instanceof RoundRobinLoadBalancingStrategy);
 	}
+	
+	@Test
+	public void testWithMoreThenOneSubscriber() {
+		final DirectChannel channel = new DirectChannel();
+		final Log logger = mock(Log.class);
+		ReflectionUtils.doWithFields(AbstractMessageChannel.class, new FieldCallback() {
+			
+			public void doWith(Field field) throws IllegalArgumentException,
+					IllegalAccessException {
+				if ("logger".equals(field.getName())){
+					field.setAccessible(true);
+					field.set(channel, logger);
+				}
+			}
+		});
+		channel.subscribe(mock(MessageHandler.class));
+		verify(logger, times(0)).info(Mockito.anyString());
+		channel.subscribe(mock(MessageHandler.class));
+		verify(logger, times(1)).info(Mockito.anyString());
+	}
 
 	@Test
 	public void testSendInSeparateThread() throws InterruptedException {