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}