/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.camel.impl;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.TimeUnit;
import org.apache.camel.Consumer;
import org.apache.camel.Endpoint;
import org.apache.camel.Exchange;
import org.apache.camel.PollingConsumerPollingStrategy;
import org.apache.camel.Processor;
import org.apache.camel.spi.ExceptionHandler;
import org.apache.camel.util.ServiceHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A default implementation of the {@link org.apache.camel.PollingConsumer} which uses the normal
* asynchronous consumer mechanism along with a {@link BlockingQueue} to allow
* the caller to pull messages on demand.
*
* @version
*/
public class EventDrivenPollingConsumer extends PollingConsumerSupport implements Processor {
private static final Logger LOG = LoggerFactory.getLogger(EventDrivenPollingConsumer.class);
private final BlockingQueue<Exchange> queue;
private ExceptionHandler interruptedExceptionHandler;
private Consumer consumer;
public EventDrivenPollingConsumer(Endpoint endpoint) {
this(endpoint, new ArrayBlockingQueue<Exchange>(1000));
}
public EventDrivenPollingConsumer(Endpoint endpoint, BlockingQueue<Exchange> queue) {
super(endpoint);
this.queue = queue;
this.interruptedExceptionHandler = new LoggingExceptionHandler(endpoint.getCamelContext(), EventDrivenPollingConsumer.class);
}
public Exchange receiveNoWait() {
return receive(0);
}
public Exchange receive() {
// must be started
if (!isRunAllowed() || !isStarted()) {
throw new RejectedExecutionException(this + " is not started, but in state: " + getStatus().name());
}
while (isRunAllowed()) {
try {
beforePoll(0);
// take will block waiting for message
return queue.take();
} catch (InterruptedException e) {
handleInterruptedException(e);
} finally {
afterPoll();
}
}
LOG.trace("Consumer is not running, so returning null");
return null;
}
public Exchange receive(long timeout) {
// must be started
if (!isRunAllowed() || !isStarted()) {
throw new RejectedExecutionException(this + " is not started, but in state: " + getStatus().name());
}
try {
// use the timeout value returned from beforePoll
timeout = beforePoll(timeout);
return queue.poll(timeout, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
handleInterruptedException(e);
return null;
} finally {
afterPoll();
}
}
public void process(Exchange exchange) throws Exception {
queue.offer(exchange);
}
public ExceptionHandler getInterruptedExceptionHandler() {
return interruptedExceptionHandler;
}
public void setInterruptedExceptionHandler(ExceptionHandler interruptedExceptionHandler) {
this.interruptedExceptionHandler = interruptedExceptionHandler;
}
protected void handleInterruptedException(InterruptedException e) {
getInterruptedExceptionHandler().handleException(e);
}
protected long beforePoll(long timeout) {
if (consumer instanceof PollingConsumerPollingStrategy) {
PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
try {
timeout = strategy.beforePoll(timeout);
} catch (Exception e) {
LOG.debug("Error occurred before polling " + consumer + ". This exception will be ignored.", e);
}
}
return timeout;
}
protected void afterPoll() {
if (consumer instanceof PollingConsumerPollingStrategy) {
PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
try {
strategy.afterPoll();
} catch (Exception e) {
LOG.debug("Error occurred after polling " + consumer + ". This exception will be ignored.", e);
}
}
}
protected void doStart() throws Exception {
// lets add ourselves as a consumer
consumer = getEndpoint().createConsumer(this);
// if the consumer has a polling strategy then invoke that
if (consumer instanceof PollingConsumerPollingStrategy) {
PollingConsumerPollingStrategy strategy = (PollingConsumerPollingStrategy) consumer;
strategy.onInit();
} else {
ServiceHelper.startService(consumer);
}
}
protected void doStop() throws Exception {
ServiceHelper.stopService(consumer);
}
protected void doShutdown() throws Exception {
ServiceHelper.stopAndShutdownService(consumer);
}
}