001 /**
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one or more
004 * contributor license agreements. See the NOTICE file distributed with
005 * this work for additional information regarding copyright ownership.
006 * The ASF licenses this file to You under the Apache License, Version 2.0
007 * (the "License"); you may not use this file except in compliance with
008 * the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.camel;
019
020 /**
021 * Represents a <a href="http://activemq.apache.org/camel/polling-consumer.html">Polling Consumer</a> where the caller
022 * polls for messages when it is ready.
023 *
024 * @version $Revision: 1.1 $
025 */
026 public interface PollingConsumer<E extends Exchange> extends Consumer<E> {
027
028 /**
029 * Waits until a message is available and then returns it. Warning that this method
030 * could block indefinitely if no messages are available.
031 *
032 * @return the message exchange received.
033 */
034 E receive();
035
036 /**
037 * Attempts to receive a message exchange immediately without waiting
038 * and returning null if a message exchange is not available yet.
039 *
040 * @return the message exchange if one is immediately available otherwise null
041 */
042 E receiveNoWait();
043
044 /**
045 * Attempts to receive a message exchange, waiting up to the given timeout to expire
046 * if a message is not yet available
047 *
048 * @param timeout the amount of time in milliseconds to wait for a message before timing out and
049 * returning null
050 *
051 * @return the message exchange if one iwas available within the timeout period, or null if the timeout expired
052 */
053 E receive(long timeout);
054
055 }