204 lines
7.7 KiB
HTML
204 lines
7.7 KiB
HTML
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<html>
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<head>
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<title>HornetQ JMS XA Receive Example</title>
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<link rel="stylesheet" type="text/css" href="../common/common.css" />
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<link rel="stylesheet" type="text/css" href="../common/prettify.css" />
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<script type="text/javascript" src="../common/prettify.js"></script>
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</head>
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<body onload="prettyPrint()">
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<h1>JMS XA Receive Example</h1>
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<p>This example demonstrates receiving a message within the scope of an XA transaction. When using an XA transaction
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the message will only be acknowledged and removed from the queue when the transaction is committed.
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If the transaction is not committed the message maybe redelivered after rollback or during XA recovery.</p>
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<p>HornetQ is JTA aware, meaning you can use HornetQ in an XA transactional environment
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and participate in XA transactions. It provides the javax.transaction.xa.XAResource interface for that
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purpose. Users can get a XAConnectionFactory to create XAConnections and XASessions.</p>
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<p>In this example we simulate a transaction manager to control the transactions. First we create an XASession
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for receiving and a normal session for sending. Then we start a new xa transaction and enlist the receiving
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XASession through its XAResource. We then send two words, 'hello' and 'world', receive them, and let the
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transaction roll back. The received messages are cancelled back to the queue. Next we start
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a new transaction with the same XAResource enlisted, but this time we commit the transaction after receiving the
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messages. Then we check that no more messages are to be received.</p>
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<h2>Example step-by-step</h2>
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<p><i>To run the example, simply type <code>mvn verify</code> from this directory</i></p>
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<ol>
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<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>client-jndi.properties</code> file in the directory <code>../common/config</code></li>
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<pre class="prettyprint">
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<code>InitialContext initialContext = getContext(0);</code>
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</pre>
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<li>We look-up the JMS queue object from JNDI</li>
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<pre class="prettyprint">
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<code>Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");</code>
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</pre>
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<li>We perform a lookup on the XA Connection Factory</li>
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<pre class="prettyprint">
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<code>XAConnectionFactory cf = (XAConnectionFactory) initialContext.lookup("/XAConnectionFactory");</code>
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</pre>
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<li>We create a JMS XAConnection</li>
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<pre class="prettyprint">
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<code>connection = cf.createXAConnection();</code>
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</pre>
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<li>We Start the connection</li>
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<pre class="prettyprint">
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<code>connection.start();</code>
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</pre>
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<li>We create a JMS XASession</li>
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<pre class="prettyprint">
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<code>XASession xaSession = connection.createXASession();</code>
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</pre>
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<li>We create a normal session</li>
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<pre class="prettyprint">
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<code>Session normalSession = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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</pre>
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<li>We create a normal Message Producer</li>
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<pre class="prettyprint">
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<code>
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MessageProducer normalProducer = normalSession.createProducer(queue);
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</code>
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</pre>
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<li>We get the JMS Session</li>
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<pre class="prettyprint">
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<code>Session session = xaSession.getSession();</code>
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</pre>
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<li>We create a message consumer</li>
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<pre class="prettyprint">
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<code>MessageConsumer xaConsumer = session.createConsumer(queue); </code>
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</pre>
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<li>We create two Text Messages</li>
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<pre class="prettyprint">
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<code>
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TextMessage helloMessage = session.createTextMessage("hello");
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TextMessage worldMessage = session.createTextMessage("world");
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</code>
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</pre>
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<li>We create a transaction</li>
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<pre class="prettyprint">
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<code>Xid xid1 = new XidImpl("xa-example1".getBytes(), 1, UUIDGenerator.getInstance().generateStringUUID().getBytes());</code>
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</pre>
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<li>We get the JMS XAResource</li>
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<pre class="prettyprint">
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<code>XAResource xaRes = xaSession.getXAResource();</code>
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</pre>
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<li>We begin the Transaction work</li>
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<pre class="prettyprint">
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<code>xaRes.start(xid1, XAResource.TMNOFLAGS);</code>
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</pre>
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<li>We send two messages.</li>
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<pre class="prettyprint">
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<code>
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normalProducer.send(helloMessage);
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normalProducer.send(worldMessage);
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</code>
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</pre>
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<li>We receive the messages</li>
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<pre class="prettyprint">
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<code>
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TextMessage rm1 = (TextMessage)xaConsumer.receive();
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System.out.println("Message received: " + rm1.getText());
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TextMessage rm2 = (TextMessage)xaConsumer.receive();
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System.out.println("Message received: " + rm2.getText());
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</code>
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</pre>
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<li>We stop the work</li>
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<pre class="prettyprint">
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<code>xaRes.end(xid1, XAResource.TMSUCCESS);</code>
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</pre>
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<li>We prepare</li>
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<pre class="prettyprint">
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<code>xaRes.prepare(xid1);</code>
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</pre>
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<li>We roll back the transaction </li>
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<pre class="prettyprint">
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<code>xaRes.rollback(xid1);</code>
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</pre>
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<li>We create another transaction </li>
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<pre class="prettyprint">
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<code>Xid xid2 = new XidImpl("xa-example2".getBytes(), 1, UUIDGenerator.getInstance().generateStringUUID().getBytes());</code>
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</pre>
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<li>We start the transaction</li>
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<pre class="prettyprint">
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<code>xaRes.start(xid2, XAResource.TMNOFLAGS);</code>
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</pre>
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<li>We receive those messages again</li>
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<pre class="prettyprint">
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<code>
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rm1 = (TextMessage)xaConsumer.receive();
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System.out.println("Message received again: " + rm1.getText());
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rm2 = (TextMessage)xaConsumer.receive();
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System.out.println("Message received again: " + rm2.getText());
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</code>
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</pre>
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<li>We stop the work</li>
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<pre class="prettyprint">
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<code>xaRes.end(xid2, XAResource.TMSUCCESS);</code>
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</pre>
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<li>We prepare</li>
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<pre class="prettyprint">
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<code>xaRes.prepare(xid2);</code>
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</pre>
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<li>We commit!</li>
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<pre class="prettyprint">
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<code>xaRes.commit(xid2, false);</code>
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</pre>
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<li>We check that no more messages are received.</li>
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<pre class="prettyprint">
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<code>
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TextMessage rm3 = (TextMessage)xaConsumer.receive(2000);
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if (rm3 == null)
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{
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System.out.println("No message received after commit.");
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}
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else
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{
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result = false;
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}
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</code>
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</pre>
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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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<pre class="prettyprint">
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<code>finally
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{
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if (initialContext != null)
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{
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initialContext.close();
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}
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if (connection != null)
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{
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connection.close();
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}
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}</code>
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</pre>
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</ol>
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</body>
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</html>
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