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.RejectedExecutionException;
022 import java.util.concurrent.TimeUnit;
023
024 import org.apache.camel.Consumer;
025 import org.apache.camel.Endpoint;
026 import org.apache.camel.Exchange;
027 import org.apache.camel.PollingConsumerPollingStrategy;
028 import org.apache.camel.Processor;
029 import org.apache.camel.spi.ExceptionHandler;
030 import org.apache.camel.util.ServiceHelper;
031 import org.slf4j.Logger;
032 import org.slf4j.LoggerFactory;
033
034 /**
035 * A default implementation of the {@link org.apache.camel.PollingConsumer} which uses the normal
036 * asynchronous consumer mechanism along with a {@link BlockingQueue} to allow
037 * the caller to pull messages on demand.
038 *
039 * @version
040 */
041 public class EventDrivenPollingConsumer extends PollingConsumerSupport implements Processor {
042 private static final transient Logger LOG = LoggerFactory.getLogger(EventDrivenPollingConsumer.class);
043 private final BlockingQueue<Exchange> queue;
044 private ExceptionHandler interruptedExceptionHandler = new LoggingExceptionHandler(EventDrivenPollingConsumer.class);
045 private Consumer consumer;
046
047 public EventDrivenPollingConsumer(Endpoint endpoint) {
048 this(endpoint, new ArrayBlockingQueue<Exchange>(1000));
049 }
050
051 public EventDrivenPollingConsumer(Endpoint endpoint, BlockingQueue<Exchange> queue) {
052 super(endpoint);
053 this.queue = queue;
054 }
055
056 public Exchange receiveNoWait() {
057 return receive(0);
058 }
059
060 public Exchange receive() {
061 // must be started
062 if (!isRunAllowed() || !isStarted()) {
063 throw new RejectedExecutionException(this + " is not started, but in state: " + getStatus().name());
064 }
065
066 while (isRunAllowed()) {
067 try {
068 beforePoll(0);
069 // take will block waiting for message
070 return queue.take();
071 } catch (InterruptedException e) {
072 handleInterruptedException(e);
073 } finally {
074 afterPoll();
075 }
076 }
077 LOG.trace("Consumer is not running, so returning null");
078 return null;
079 }
080
081 public Exchange receive(long timeout) {
082 // must be started
083 if (!isRunAllowed() || !isStarted()) {
084 throw new RejectedExecutionException(this + " is not started, but in state: " + getStatus().name());
085 }
086
087 try {
088 // use the timeout value returned from beforePoll
089 timeout = beforePoll(timeout);
090 return queue.poll(timeout, TimeUnit.MILLISECONDS);
091 } catch (InterruptedException e) {
092 handleInterruptedException(e);
093 return null;
094 } finally {
095 afterPoll();
096 }
097 }
098
099 public void process(Exchange exchange) throws Exception {
100 queue.offer(exchange);
101 }
102
103 public ExceptionHandler getInterruptedExceptionHandler() {
104 return interruptedExceptionHandler;
105 }
106
107 public void setInterruptedExceptionHandler(ExceptionHandler interruptedExceptionHandler) {
108 this.interruptedExceptionHandler = interruptedExceptionHandler;
109 }
110
111 protected void handleInterruptedException(InterruptedException e) {
112 getInterruptedExceptionHandler().handleException(e);
113 }
114
115 protected long beforePoll(long timeout) {
116 if (consumer instanceof PollingConsumerPollingStrategy) {
117 PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
118 try {
119 timeout = strategy.beforePoll(timeout);
120 } catch (Exception e) {
121 LOG.debug("Error occurred before polling " + consumer + ". This exception will be ignored.", e);
122 }
123 }
124 return timeout;
125 }
126
127 protected void afterPoll() {
128 if (consumer instanceof PollingConsumerPollingStrategy) {
129 PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
130 try {
131 strategy.afterPoll();
132 } catch (Exception e) {
133 LOG.debug("Error occurred after polling " + consumer + ". This exception will be ignored.", e);
134 }
135 }
136 }
137
138 protected void doStart() throws Exception {
139 // lets add ourselves as a consumer
140 consumer = getEndpoint().createConsumer(this);
141
142 // if the consumer has a polling strategy then invoke that
143 if (consumer instanceof PollingConsumerPollingStrategy) {
144 PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
145 strategy.onInit();
146 } else {
147 // for regular consumers start it
148 ServiceHelper.startService(consumer);
149 }
150 }
151
152 protected void doStop() throws Exception {
153 ServiceHelper.stopService(consumer);
154 }
155
156 protected void doShutdown() throws Exception {
157 ServiceHelper.stopAndShutdownService(consumer);
158 }
159 }