001/*
002 * Copyright 2002-2014 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.messaging.support;
018
019import org.springframework.messaging.Message;
020import org.springframework.messaging.MessageChannel;
021import org.springframework.messaging.MessageHandler;
022
023/**
024 * An extension of {@link ChannelInterceptor} with callbacks to intercept the
025 * asynchronous sending of a {@link org.springframework.messaging.Message} to
026 * a specific subscriber through an {@link java.util.concurrent.Executor}.
027 * Supported on {@link org.springframework.messaging.MessageChannel}
028 * implementations that can be configured with an Executor.
029 *
030 * @author Rossen Stoyanchev
031 * @since 4.1
032 */
033public interface ExecutorChannelInterceptor extends ChannelInterceptor {
034
035        /**
036         * Invoked inside the {@link Runnable} submitted to the Executor just before
037         * calling the target MessageHandler to handle the message. Allows for
038         * modification of the Message if necessary or when {@code null} is returned
039         * the MessageHandler is not invoked.
040         * @param message the message to be handled
041         * @param channel the channel on which the message was sent to
042         * @param handler the target handler to handle the message
043         * @return the input message, or a new instance, or {@code null}
044         */
045        Message<?> beforeHandle(Message<?> message, MessageChannel channel, MessageHandler handler);
046
047        /**
048         * Invoked inside the {@link Runnable} submitted to the Executor after calling
049         * the target MessageHandler regardless of the outcome (i.e. Exception raised
050         * or not) thus allowing for proper resource cleanup.
051         * <p>Note that this will be invoked only if beforeHandle successfully completed
052         * and returned a Message, i.e. it did not return {@code null}.
053         * @param message the message handled
054         * @param channel the channel on which the message was sent to
055         * @param handler the target handler that handled the message
056         * @param ex any exception that may been raised by the handler
057         */
058        void afterMessageHandled(Message<?> message, MessageChannel channel, MessageHandler handler, Exception ex);
059
060}