/*
* 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 org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
/**
* Interface for interceptors that are able to view and/or modify the
* {@link Message Messages} being sent-to and/or received-from a
* {@link MessageChannel}.
*
* @author Mark Fisher
* @author Rossen Stoyanchev
* @since 4.0
*/
public interface ChannelInterceptor {
/**
* Invoked before the Message is actually sent to the channel.
* This allows for modification of the Message if necessary.
* If this method returns {@code null} then the actual
* send invocation will not occur.
*/
Message<?> preSend(Message<?> message, MessageChannel channel);
/**
* Invoked immediately after the send invocation. The boolean
* value argument represents the return value of that invocation.
*/
void postSend(Message<?> message, MessageChannel channel, boolean sent);
/**
* Invoked after the completion of a send regardless of any exception that
* have been raised thus allowing for proper resource cleanup.
* <p>Note that this will be invoked only if {@link #preSend} successfully
* completed and returned a Message, i.e. it did not return {@code null}.
* @since 4.1
*/
void afterSendCompletion(Message<?> message, MessageChannel channel, boolean sent, Exception ex);
/**
* Invoked as soon as receive is called and before a Message is
* actually retrieved. If the return value is 'false', then no
* Message will be retrieved. This only applies to PollableChannels.
*/
boolean preReceive(MessageChannel channel);
/**
* Invoked immediately after a Message has been retrieved but before
* it is returned to the caller. The Message may be modified if
* necessary. This only applies to PollableChannels.
*/
Message<?> postReceive(Message<?> message, MessageChannel channel);
/**
* Invoked after the completion of a receive regardless of any exception that
* have been raised thus allowing for proper resource cleanup.
* <p>Note that this will be invoked only if {@link #preReceive} successfully
* completed and returned {@code true}.
* @since 4.1
*/
void afterReceiveCompletion(Message<?> message, MessageChannel channel, Exception ex);
}