Add InterceptableChannel

The new contract allows registration of interceptors with any
MessageChannel implementation hierarchy -- for example the one in the
Spring Framework or the one in Spring Integration.

spring-messaging/src/main/java/org/springframework/messaging/support/AbstractMessageChannel.java

@@ -37,7 +37,7 @@ import org.springframework.util.ObjectUtils;
  * @author Rossen Stoyanchev
  * @since 4.0
  */
-public abstract class AbstractMessageChannel implements MessageChannel, BeanNameAware  {
+public abstract class AbstractMessageChannel implements MessageChannel, BeanNameAware, InterceptableChannel  {
 
 	protected final Log logger = LogFactory.getLog(getClass());
 
@@ -66,42 +66,40 @@ public abstract class AbstractMessageChannel implements MessageChannel, BeanName
 		return this.beanName;
 	}
 
-	/**
-	 * Set the list of channel interceptors. This will clear any existing interceptors.
-	 */
+	@Override
 	public void setInterceptors(List<ChannelInterceptor> interceptors) {
 		this.interceptors.clear();
 		this.interceptors.addAll(interceptors);
 	}
 
-	/**
-	 * Add a channel interceptor to the end of the list.
-	 */
+	@Override
 	public void addInterceptor(ChannelInterceptor interceptor) {
 		this.interceptors.add(interceptor);
 	}
 
-	/**
-	 * Add a channel interceptor at the specified index.
-	 */
+	@Override
 	public void addInterceptor(int index, ChannelInterceptor interceptor) {
 		this.interceptors.add(index, interceptor);
 	}
 
 	/**
-	 * Return a read-only list of the configured interceptors.
+	 * {@inheritDoc}
+	 * <p>The returned list is read-only.
 	 */
+	@Override
 	public List<ChannelInterceptor> getInterceptors() {
 		return Collections.unmodifiableList(this.interceptors);
 	}
 
-	/**
-	 * Remove the given interceptor.
-	 */
+	@Override
 	public boolean removeInterceptor(ChannelInterceptor interceptor) {
 		return this.interceptors.remove(interceptor);
 	}
 
+	@Override
+	public ChannelInterceptor removeInterceptor(int index) {
+		return this.interceptors.remove(index);
+	}
 
 	@Override
 	public final boolean send(Message<?> message) {

spring-messaging/src/main/java/org/springframework/messaging/support/InterceptableChannel.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2014 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.messaging.support;
+
+import java.util.List;
+
+/**
+ * A {@link org.springframework.messaging.MessageChannel MessageChannel} that
+ * maintains a list {@link org.springframework.messaging.support.ChannelInterceptor
+ * ChannelInterceptors} and allows interception of message sending.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.1
+ */
+public interface InterceptableChannel {
+
+	/**
+	 * Set the list of channel interceptors clearing any existing interceptors.
+	 */
+	void setInterceptors(List<ChannelInterceptor> interceptors);
+
+	/**
+	 * Add a channel interceptor to the end of the list.
+	 */
+	void addInterceptor(ChannelInterceptor interceptor);
+
+	/**
+	 * Add a channel interceptor at the specified index.
+	 */
+	void addInterceptor(int index, ChannelInterceptor interceptor);
+
+	/**
+	 * Return the list of configured interceptors.
+	 */
+	List<ChannelInterceptor> getInterceptors();
+
+	/**
+	 * Remove the given interceptor.
+	 */
+	boolean removeInterceptor(ChannelInterceptor interceptor);
+
+	/**
+	 * Remove the interceptor at the given index.
+	 */
+	ChannelInterceptor removeInterceptor(int index);
+
+}