001/* 002 * Copyright 2002-2018 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.lang.Nullable; 020import org.springframework.messaging.Message; 021import org.springframework.messaging.MessageChannel; 022import org.springframework.messaging.MessageHandler; 023 024/** 025 * An extension of {@link ChannelInterceptor} with callbacks to intercept the 026 * asynchronous sending of a {@link org.springframework.messaging.Message} to 027 * a specific subscriber through an {@link java.util.concurrent.Executor}. 028 * Supported on {@link org.springframework.messaging.MessageChannel} 029 * implementations that can be configured with an {@code Executor}. 030 * 031 * @author Rossen Stoyanchev 032 * @since 4.1 033 * @see Message 034 * @see MessageChannel 035 * @see MessageHandler 036 */ 037public interface ExecutorChannelInterceptor extends ChannelInterceptor { 038 039 /** 040 * Invoked inside the {@link Runnable} submitted to the Executor just before 041 * calling the target MessageHandler to handle the message. Allows for 042 * modification of the Message if necessary or when {@code null} is returned 043 * the MessageHandler is not invoked. 044 * @param message the message to be handled 045 * @param channel the channel on which the message was sent to 046 * @param handler the target handler to handle the message 047 * @return the input message, or a new instance, or {@code null} 048 */ 049 @Nullable 050 default Message<?> beforeHandle(Message<?> message, MessageChannel channel, MessageHandler handler) { 051 return message; 052 } 053 054 /** 055 * Invoked inside the {@link Runnable} submitted to the Executor after calling 056 * the target MessageHandler regardless of the outcome (i.e. Exception raised 057 * or not) thus allowing for proper resource cleanup. 058 * <p>Note that this will be invoked only if beforeHandle successfully completed 059 * and returned a Message, i.e. it did not return {@code null}. 060 * @param message the message handled 061 * @param channel the channel on which the message was sent to 062 * @param handler the target handler that handled the message 063 * @param ex any exception that may been raised by the handler 064 */ 065 default void afterMessageHandled(Message<?> message, MessageChannel channel, MessageHandler handler, 066 @Nullable Exception ex) { 067 } 068 069}