001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.camel.impl;
018
019 import java.util.concurrent.ArrayBlockingQueue;
020 import java.util.concurrent.BlockingQueue;
021 import java.util.concurrent.TimeUnit;
022
023 import org.apache.camel.Consumer;
024 import org.apache.camel.Endpoint;
025 import org.apache.camel.Exchange;
026 import org.apache.camel.PollingConsumerAware;
027 import org.apache.camel.Processor;
028 import org.apache.camel.processor.Logger;
029 import org.apache.camel.spi.ExceptionHandler;
030 import org.apache.commons.logging.Log;
031 import org.apache.commons.logging.LogFactory;
032
033 /**
034 * A default implementation of the {@link org.apache.camel.PollingConsumer} which uses the normal
035 * asynchronous consumer mechanism along with a {@link BlockingQueue} to allow
036 * the caller to pull messages on demand.
037 *
038 * @version $Revision: 761579 $
039 */
040 public class EventDrivenPollingConsumer extends PollingConsumerSupport implements Processor {
041 private static final transient Log LOG = LogFactory.getLog(EventDrivenPollingConsumer.class);
042 private BlockingQueue<Exchange> queue;
043 private ExceptionHandler interuptedExceptionHandler = new LoggingExceptionHandler(new Logger(LOG));
044 private Consumer consumer;
045
046 public EventDrivenPollingConsumer(Endpoint endpoint) {
047 this(endpoint, new ArrayBlockingQueue<Exchange>(1000));
048 }
049
050 public EventDrivenPollingConsumer(Endpoint endpoint, BlockingQueue<Exchange> queue) {
051 super(endpoint);
052 this.queue = queue;
053 }
054
055 public Exchange receiveNoWait() {
056 return receive(0);
057 }
058
059 public Exchange receive() {
060 while (isRunAllowed()) {
061 try {
062 return queue.take();
063 } catch (InterruptedException e) {
064 handleInteruptedException(e);
065 }
066 }
067 if (LOG.isTraceEnabled()) {
068 LOG.trace("Consumer is not running, so returning null");
069 }
070 return null;
071 }
072
073 public Exchange receive(long timeout) {
074 try {
075 return queue.poll(timeout, TimeUnit.MILLISECONDS);
076 } catch (InterruptedException e) {
077 handleInteruptedException(e);
078 return null;
079 }
080 }
081
082 public void process(Exchange exchange) throws Exception {
083 if (exchange instanceof PollingConsumerAware) {
084 // callback that this exchange has been polled
085 ((PollingConsumerAware)exchange).exchangePolled(exchange);
086 }
087 queue.offer(exchange);
088 }
089
090 public ExceptionHandler getInteruptedExceptionHandler() {
091 return interuptedExceptionHandler;
092 }
093
094 public void setInteruptedExceptionHandler(ExceptionHandler interuptedExceptionHandler) {
095 this.interuptedExceptionHandler = interuptedExceptionHandler;
096 }
097
098 protected void handleInteruptedException(InterruptedException e) {
099 getInteruptedExceptionHandler().handleException(e);
100 }
101
102 protected void doStart() throws Exception {
103 // lets add ourselves as a consumer
104 consumer = getEndpoint().createConsumer(this);
105 consumer.start();
106 }
107
108 protected void doStop() throws Exception {
109 if (consumer != null) {
110 try {
111 consumer.stop();
112 } finally {
113 consumer = null;
114 }
115 }
116 }
117 }