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<h1>Java EE MDB Remote Failover Example</h1>
<p>This example shows you how to send a message to an MDB that is configured to consume from a live/backup pair.</p>
<p>The example will send deploy a simple MDB to one Wildfly instance. Then it will send a message to the live server of the live/backup pair
which will be consumed by the MDB after which the MDB will send a reply message which will be consumed by the example program. Then the live
server will be stopped so that the backup takes over and the process will be repeated.</p>
<p>Unlike the "Java EE MDB Remote Failover Static Example," this example uses a "dynamic" configuration for finding all the nodes. In other words
it uses UDP multicast for server discovery.</p>
<p>The example leverages the JBoss Arquillian framework to run a WildFly instance and deploy the MDB.</p>
<h2>Example step-by-step</h2>
<p><i>download WildFly 8.0.0.Final from <a href="http://wildfly.org/downloads/">here</a> and install.</i></p>
<p><i>set the JBOSS_HOME property to point to the WildFly install directory</i></p>
<p><i>type <code>mvn verify</code> from the example directory to run</i></p>
<ol>
<li>First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get it's properties from the <code>jndi.properties</code> file in the directory <code>config</code></li>
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final Properties env = new Properties();
env.put(Context.INITIAL_CONTEXT_FACTORY, "org.jboss.naming.remote.client.InitialContextFactory");
env.put(Context.PROVIDER_URL, "http-remoting://localhost:8080");
initialContext = new InitialContext(env);
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<li>We look up the JMS queue object from JNDI</li>
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Queue queue = (Queue) initialContext.lookup("/queues/inQueue");
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<li>We look up the JMS connection factory object from JNDI</li>
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ConnectionFactory cf = (ConnectionFactory)initialContext.lookup("/jms/RemoteConnectionFactory");
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<li>We create a JMS connection</li>
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connection = cf.createConnection("guest", "password");
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<li>We create a JMS session. The session is created as non transacted and will auto acknowledge messages.</li>
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<code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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<li>We create a JMS message producer on the session. This will be used to send the messages.</li>
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<code>MessageProducer messageProducer = session.createProducer(queue);</code>
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<li>We create a JMS text messages that we are going to send.</li>
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<code>TextMessage message = session.createTextMessage("This is a text message");</code>
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<li>We send the message to the queue</li>
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<code>messageProducer.send(message);</code>
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<li>MDB receives the message</li>
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<code>TextMessage textMessage = (TextMessage)message;</code>
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<li>Get and print the text</li>
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<code>String text = textMessage.getText();
System.out.println("message " + text);</code>
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<li>Create a JMS connection using the injected connection factory</li>
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<code>conn = connectionFactory.createConnection();</code>
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<li>Create a JMS session</li>
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<code>Session sess = conn.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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<li>Create a producer</li>
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<code>MessageProducer producer = sess.createProducer(replyQueue);</code>
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<li>Create a message and send it to the reply queue</li>
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<code>producer.send(sess.createTextMessage("this is a reply"));</code>
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<li>Client looks up the reply queue</li>
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<code>queue = (Queue) initialContext.lookup("/queues/outQueue");</code>
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<li>Create a consumer</li>
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<code>MessageConsumer messageConsumer = session.createConsumer(queue);</code>
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<li>Start the connection</li>
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<code>connection.start();</code>
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<li>Receive the message and print it out</li>
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<code>message = (TextMessage) messageConsumer.receive(20000);
System.out.println("message.getText() = " + message.getText());</code>
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<li>Kill the live server. At this point both the standalone client and the MDB will fail-over to the backup.</li>
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<code>killer.kill();</code>
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<li>Create another message</li>
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<code>message = session.createTextMessage("This is another text message");</code>
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<li>Send the message</li>
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<code>producer.send(message);</code>
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<li>The MDB will receive the message and send another message to the reply queue which the client then receives</li>
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<code>message = (TextMessage) messageConsumer.receive(20000);</code>
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<li>And finally, <b>always</b> remember to close your JMS connections and resources after use, in a <code>finally</code> block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects</li>
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<code>finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}</code>
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