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; 021 022/** 023 * Interface for interceptors that are able to view and/or modify the 024 * {@link Message Messages} being sent-to and/or received-from a 025 * {@link MessageChannel}. 026 * 027 * @author Mark Fisher 028 * @author Rossen Stoyanchev 029 * @since 4.0 030 */ 031public interface ChannelInterceptor { 032 033 /** 034 * Invoked before the Message is actually sent to the channel. 035 * This allows for modification of the Message if necessary. 036 * If this method returns {@code null} then the actual 037 * send invocation will not occur. 038 */ 039 Message<?> preSend(Message<?> message, MessageChannel channel); 040 041 /** 042 * Invoked immediately after the send invocation. The boolean 043 * value argument represents the return value of that invocation. 044 */ 045 void postSend(Message<?> message, MessageChannel channel, boolean sent); 046 047 /** 048 * Invoked after the completion of a send regardless of any exception that 049 * have been raised thus allowing for proper resource cleanup. 050 * <p>Note that this will be invoked only if {@link #preSend} successfully 051 * completed and returned a Message, i.e. it did not return {@code null}. 052 * @since 4.1 053 */ 054 void afterSendCompletion(Message<?> message, MessageChannel channel, boolean sent, Exception ex); 055 056 /** 057 * Invoked as soon as receive is called and before a Message is 058 * actually retrieved. If the return value is 'false', then no 059 * Message will be retrieved. This only applies to PollableChannels. 060 */ 061 boolean preReceive(MessageChannel channel); 062 063 /** 064 * Invoked immediately after a Message has been retrieved but before 065 * it is returned to the caller. The Message may be modified if 066 * necessary. This only applies to PollableChannels. 067 */ 068 Message<?> postReceive(Message<?> message, MessageChannel channel); 069 070 /** 071 * Invoked after the completion of a receive regardless of any exception that 072 * have been raised thus allowing for proper resource cleanup. 073 * <p>Note that this will be invoked only if {@link #preReceive} successfully 074 * completed and returned {@code true}. 075 * @since 4.1 076 */ 077 void afterReceiveCompletion(Message<?> message, MessageChannel channel, Exception ex); 078 079}