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<h1>EJB/JMS Transaction Example</h1>
<p>The example application will invoke an EJB which is deployed within WildFly which will:</p>
<ol>
<li>start an XA transaction</li>
<li>send a JMS message</li>
<li>update an in-memory database</li>
<li>commit the transaction</li>
</ol>
<p>The example application will then receive the message sent by the EJB.</p>
<h2>WildFly configuration</h2>
<p>The example leverages the 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>
<p>The example code is composed of two main classes:</p>
<ul>
<li><code>EJBClientExample</code></li> - the example application
<li><code>SendMessageBean</code></li> - a Stateless EJB with a remote interface
</ul>
<h3>Example Application</h3>
<p>Let's take a look at EJBClientExample first.</p>
<ol>
<li>First we need to get an initial context so we can look-up the EJB. This initial context will get it's properties from the jboss-ejb-client.properties.</li>
<pre class="prettyprint">
Properties env = new Properties();
env.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
InitialContext initialContext = new InitialContext();
</pre>
<li>We look up the EJB</li>
<pre class="prettyprint">
SendMessageService service = (SendMessageService) initialContext.lookup("ejb:/test//SendMessageBean!org.apache.activemq.javaee.example.server.SendMessageService");
</pre>
<li>We create the DB table which will be updated if it does not already exist</li>
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service.createTable();
</pre>
<li>We invoke the EJB's <code>sendAndUpdate</code> method. This method will send a JMS text message (with the text passed in parameter)
and insert a row in the database table with the text and the message's JMS Message ID</li>
<pre class="prettyprint">
service.sendAndUpdate("This is a text message");
</pre>
<p><em>We will now consume the JMS message which was sent by the EJB at step 4.</em></p>
<li>We need to get a new initial context so we can look-up the JMS connection factory and destination objects from JNDI.</li>
<pre class="prettyprint">
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);
</pre>
<li>We look up the JMS connection factory</li>
<pre class="prettyprint">
ConnectionFactory cf = (ConnectionFactory)initialContext.lookup("jms/RemoteConnectionFactory");
</pre>
<li>We lookup the JMS queue</li>
<pre class="prettyprint">
Queue queue = (Queue)initialContext.lookup("jms/queues/testQueue");
</pre>
<li>We create a connection, a session and a message consumer for the queue</li>
<pre class="prettyprint">
connection = cf.createConnection("guest", "password");
Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageConsumer consumer = session.createConsumer(queue);
</pre>
<li>We start the JMS connection</li>
<pre class="prettyprint">
connection.start();
</pre>
<li>We receive a message from the queue. It corresponds to the message sent by the EJB</li>
<pre class="prettyprint">
TextMessage messageReceived = (TextMessage)consumer.receive(5000);
System.out.println("Received message: " + messageReceived.getText() + " (" + messageReceived.getJMSMessageID() + ")");
</pre>
<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>
<pre class="prettyprint">
finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}
</pre>
</ol>
<h3>EJB Example</h3>
<p>Let's now take a look at the EJB example</p>
<ol>
<li>First, we create a new initial context</li>
<pre class="prettyprint">
ic = new InitialContext();
</pre>
<li>We look up the JMS <em>XA</em> Connection Factory (which is bound to <code>java:/JmsXA</code>)</li>
<pre class="prettyprint">
ConnectionFactory cf = (ConnectionFactory)ic.lookup("java:/JmsXA");
</pre>
<li>We look up the JMS Queue</li>
<pre class="prettyprint">
Queue queue = (Queue)ic.lookup("queue/testQueue");
</pre>
<li>We create a JMS connection, a session and a message producer for the queue</li>
<pre class="prettyprint">
jmsConnection = cf.createConnection();
Session session = jmsConnection.createSession(false, Session.AUTO_ACKNOWLEDGE);
MessageProducer messageProducer = session.createProducer(queue);
</pre>
<li>We create a text message with the text passed in parameter of the EJB method</li>
<pre class="prettyprint">
TextMessage message = session.createTextMessage(text);
</pre>
<li>We send the message to the queue</li>
<pre class="prettyprint">
messageProducer.send(message);
System.out.println("Sent message: " + message.getText() + "(" + message.getJMSMessageID() + ")");
</pre>
<li>We now lookup the JDBC <em>XA</em> DataSource</li>
<pre class="prettyprint">
DataSource ds = (DataSource)ic.lookup("java:/XADS");
</pre>
<li>We retrieve a JDBC connection</li>
<pre class="prettyprint">
jdbcConnection = ds.getConnection();
</pre>
<li>We create a prepared statement to insert the text and message's ID in the DB table</li>
<pre class="prettyprint">
PreparedStatement pr = jdbcConnection.prepareStatement("INSERT INTO " + TABLE
+ " (id, text) VALUES ('" + message.getJMSMessageID() + "', '" + text + "');");
</pre>
<li>We execute the prepared statement</li>
<pre class="prettyprint">
pr.execute();
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<li>We close the prepared statement</li>
<pre class="prettyprint">
pr.close();
</pre>
<li>And finally, <b>always</b> remember to close all your connections and resources (for both JMS and JDBC) after use, in a <code>finally</code> block.</li>
<pre class="prettyprint">
finally
{
if (ic != null)
{
ic.close();
}
if (jmsConnection != null)
{
jmsConnection.close();
}
if (jdbcConnection != null)
{
jdbcConnection.close();
}
}
</pre>
</ol>
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