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.Processor;
027    import org.apache.camel.processor.Logger;
028    import org.apache.camel.spi.ExceptionHandler;
029    import org.apache.commons.logging.Log;
030    import org.apache.commons.logging.LogFactory;
031    
032    /**
033     * A default implementation of the {@link org.apache.camel.PollingConsumer} which uses the normal
034     * asynchronous consumer mechanism along with a {@link BlockingQueue} to allow
035     * the caller to pull messages on demand.
036     *
037     * @version $Revision: 751655 $
038     */
039    public class EventDrivenPollingConsumer extends PollingConsumerSupport implements Processor {
040        private static final transient Log LOG = LogFactory.getLog(EventDrivenPollingConsumer.class);
041        private BlockingQueue<Exchange> queue;
042        private ExceptionHandler interuptedExceptionHandler = new LoggingExceptionHandler(new Logger(LOG));
043        private Consumer consumer;
044    
045        public EventDrivenPollingConsumer(Endpoint endpoint) {
046            this(endpoint, new ArrayBlockingQueue<Exchange>(1000));
047        }
048    
049        public EventDrivenPollingConsumer(Endpoint endpoint, BlockingQueue<Exchange> queue) {
050            super(endpoint);
051            this.queue = queue;
052        }
053    
054        public Exchange receiveNoWait() {
055            return receive(0);
056        }
057    
058        public Exchange receive() {
059            while (isRunAllowed()) {
060                try {
061                    return queue.take();
062                } catch (InterruptedException e) {
063                    handleInteruptedException(e);
064                }
065            }
066            if (LOG.isTraceEnabled()) {
067                LOG.trace("Consumer is not running, so returning null");
068            }
069            return null;
070        }
071    
072        public Exchange receive(long timeout) {
073            try {
074                return queue.poll(timeout, TimeUnit.MILLISECONDS);
075            } catch (InterruptedException e) {
076                handleInteruptedException(e);
077                return null;
078            }
079        }
080    
081        public void process(Exchange exchange) throws Exception {
082            queue.offer(exchange);
083        }
084    
085        public ExceptionHandler getInteruptedExceptionHandler() {
086            return interuptedExceptionHandler;
087        }
088    
089        public void setInteruptedExceptionHandler(ExceptionHandler interuptedExceptionHandler) {
090            this.interuptedExceptionHandler = interuptedExceptionHandler;
091        }
092    
093        protected void handleInteruptedException(InterruptedException e) {
094            getInteruptedExceptionHandler().handleException(e);
095        }
096    
097        protected void doStart() throws Exception {
098            // lets add ourselves as a consumer
099            consumer = getEndpoint().createConsumer(this);
100            consumer.start();
101        }
102    
103        protected void doStop() throws Exception {
104            if (consumer != null) {
105                try {
106                    consumer.stop();
107                } finally {
108                    consumer = null;
109                }
110            }
111        }
112    }