Added a DefaultErrorChannel implementation to be used by the MessageBus. Provided a key for the error channel name: MessageBus.ERROR_CHANNEL_NAME (INT-119). Removed the getErrorChannel and setErrorChannel() methods from the ChannelRegistry interface (since the key can be used to do a lookup). MessageBus still provides convenience methods.

spring-integration-core/src/main/java/org/springframework/integration/bus/DefaultErrorChannel.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2002-2007 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.integration.bus;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.integration.channel.MessageChannel;
+import org.springframework.integration.channel.SimpleChannel;
+import org.springframework.integration.channel.interceptor.ChannelInterceptorAdapter;
+import org.springframework.integration.message.Message;
+
+/**
+ * The default error channel implementation used by the {@link MessageBus}.
+ * 
+ * @author Mark Fisher
+ */
+public class DefaultErrorChannel extends SimpleChannel {
+
+	private final Log logger = LogFactory.getLog(this.getClass());
+
+
+	public DefaultErrorChannel() {
+		this.addInterceptor(new ErrorLoggingInterceptor());
+	}
+
+
+	private class ErrorLoggingInterceptor extends ChannelInterceptorAdapter {
+
+		@Override
+		public void postSend(Message<?> message, MessageChannel channel, boolean sent) {
+			Object payload = message.getPayload();
+			if (!sent) {
+				if (logger.isWarnEnabled()) {
+					logger.warn("DefaultErrorChannel has reached capacity. Are any handlers subscribed?");
+				}
+			}
+			// if error channel has no subscribers, then errors are at least visible at debug level
+			if (logger.isDebugEnabled()) {
+				String errorMessage = "Error Received. Message: " + message.toString(); 
+				if (payload instanceof Throwable) {
+					logger.debug(errorMessage, (Throwable) payload);
+				}
+				else {
+					logger.debug(errorMessage);
+				}
+			}
+		}
+	}
+
+}

spring-integration-core/src/main/java/org/springframework/integration/bus/MessageBus.java

@@ -59,6 +59,8 @@ import org.springframework.util.Assert;
  */
 public class MessageBus implements ChannelRegistry, ApplicationContextAware, Lifecycle {
 
+	public static final String ERROR_CHANNEL_NAME = "errorChannel";
+
 	private static final int DEFAULT_DISPATCHER_POOL_SIZE = 10;
 
 
@@ -160,7 +162,7 @@ public class MessageBus implements ChannelRegistry, ApplicationContextAware, Lif
 				return;
 			}
 			if (this.getErrorChannel() == null) {
-				this.setErrorChannel(new SimpleChannel(Integer.MAX_VALUE));
+				this.setErrorChannel(new DefaultErrorChannel());
 			}
 			if (this.executor == null) {
 				this.executor = new ScheduledThreadPoolExecutor(DEFAULT_DISPATCHER_POOL_SIZE);
@@ -173,11 +175,11 @@ public class MessageBus implements ChannelRegistry, ApplicationContextAware, Lif
 	}
 
 	public MessageChannel getErrorChannel() {
-		return this.channelRegistry.getErrorChannel();
+		return this.channelRegistry.lookupChannel(ERROR_CHANNEL_NAME);
 	}
 
 	public void setErrorChannel(MessageChannel errorChannel) {
-		this.channelRegistry.setErrorChannel(errorChannel);
+		this.channelRegistry.registerChannel(ERROR_CHANNEL_NAME, errorChannel);
 	}
 
 	public MessageChannel lookupChannel(String channelName) {

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

@@ -29,8 +29,4 @@ public interface ChannelRegistry {
 
 	MessageChannel lookupChannel(String channelName);
 
-	void setErrorChannel(MessageChannel errorChannel);
-
-	MessageChannel getErrorChannel();
-
 }