001/* 002 * Copyright 2002-2013 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; 018 019/** 020 * A {@link MessageChannel} that maintains a registry of subscribers and invokes 021 * them to handle messages sent through this channel. 022 * 023 * @author Mark Fisher 024 * @since 4.0 025 */ 026public interface SubscribableChannel extends MessageChannel { 027 028 /** 029 * Register a message handler. 030 * @return {@code true} if the handler was subscribed or {@code false} if it 031 * was already subscribed. 032 */ 033 boolean subscribe(MessageHandler handler); 034 035 /** 036 * Un-register a message handler. 037 * @return {@code true} if the handler was un-registered, or {@code false} 038 * if was not registered. 039 */ 040 boolean unsubscribe(MessageHandler handler); 041 042}