/*
* 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.qpid.example.subscriber;
import org.apache.qpid.client.AMQConnectionFactory;
import javax.jms.*;
import javax.jms.Connection;
import javax.jms.MessageConsumer;
import javax.jms.Session;
import javax.naming.InitialContext;
import org.apache.qpid.example.shared.InitialContextHelper;
import org.slf4j.LoggerFactory;
import org.slf4j.Logger;
/**
* Subscriber which consumes messages from a queue
*/
public class Subscriber
{
private static final Logger _log = LoggerFactory.getLogger(Subscriber.class);
protected static Connection _connection;
protected static MessageConsumer _consumer;
protected static InitialContextHelper _contextHelper;
protected static AMQConnectionFactory _connectionFactory;
protected Destination _destination;
public Subscriber()
{
try
{
//get an initial context from default properties
_contextHelper = new InitialContextHelper(null);
InitialContext ctx = _contextHelper.getInitialContext();
//then create a connection using the AMQConnectionFactory
_connectionFactory = (AMQConnectionFactory) ctx.lookup("local");
//lookup queue from context
_destination = (Destination) ctx.lookup("MyQueue");
}
catch (Exception e)
{
e.printStackTrace();
_log.error("Exception", e);
}
}
/**
* Listener class that handles messages
*/
public static class ExampleMessageListener implements MessageListener
{
private String _name;
public ExampleMessageListener(String name)
{
_name = name;
}
/**
* Listens for message callbacks, handles and then acknowledges them
* @param message - the message received
*/
public void onMessage(javax.jms.Message message)
{
_log.info(_name + " got message '" + message + "'");
try
{
//NB: Handle your message appropriately for your application here
//do some stuff
_log.debug("Acknowledging recieved message");
//Now acknowledge the message to clear it from our queue
message.acknowledge();
}
catch(JMSException j)
{
_log.error("JMSException trying to acknowledge message receipt");
j.printStackTrace();
}
catch(Exception e)
{
_log.error("Unexpected exception trying to handle message");
e.printStackTrace();
}
}
}
/**
* Subscribes to example Queue and attaches listener
*/
public void subscribe()
{
_log.info("Starting subscription ...");
try
{
_connection = _connectionFactory.createConnection();
//Non transactional session using client acknowledgement
Session session = _connection.createSession(false, Session.CLIENT_ACKNOWLEDGE);
//Create a consumer with a destination of our queue which will use defaults for prefetch etc
_consumer = session.createConsumer(_destination);
//give the message listener a name of it's own
_consumer.setMessageListener(new ExampleMessageListener("MessageListener " + System.currentTimeMillis()));
_connection.start();
}
catch (Throwable t)
{
_log.error("Fatal error: " + t);
t.printStackTrace();
}
_log.info("Waiting for messages ...");
//wait for messages and sleep to survive failover
try
{
while(true)
{
Thread.sleep(Long.MAX_VALUE);
}
}
catch (Exception e)
{
_log.warn("Exception while Subscriber sleeping",e);
}
}
/**
* Stop consuming and close connection
*/
public void stop()
{
try
{
_consumer.close();
_consumer = null;
_connection.stop();
_connection.close();
}
catch(JMSException j)
{
_log.error("JMSException trying to Subscriber.stop: " + j.getStackTrace());
}
}
}