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 019import org.springframework.lang.Nullable; 020 021/** 022 * A {@link MessageChannel} from which messages may be actively received through polling. 023 * 024 * @author Mark Fisher 025 * @since 4.0 026 */ 027public interface PollableChannel extends MessageChannel { 028 029 /** 030 * Receive a message from this channel, blocking indefinitely if necessary. 031 * @return the next available {@link Message} or {@code null} if interrupted 032 */ 033 @Nullable 034 Message<?> receive(); 035 036 /** 037 * Receive a message from this channel, blocking until either a message is available 038 * or the specified timeout period elapses. 039 * @param timeout the timeout in milliseconds or {@link MessageChannel#INDEFINITE_TIMEOUT}. 040 * @return the next available {@link Message} or {@code null} if the specified timeout 041 * period elapses or the message reception is interrupted 042 */ 043 @Nullable 044 Message<?> receive(long timeout); 045 046}