148 lines
6.4 KiB
HTML
148 lines
6.4 KiB
HTML
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<html>
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<head>
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<title>ActiveMQ JMS QueueBrowser 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 QueueBrowser Example</h1>
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<p>This example shows you how to use a JMS <a href="http://java.sun.com/javaee/5/docs/api/javax/jms/QueueBrowser.html">QueueBrowser</a> with ActiveMQ.<br />
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Queues are a standard part of JMS, please consult the JMS 1.1 specification for full details.<br />
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A QueueBrowser is used to look at messages on the queue without removing them.
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It can scan the entire content of a queue or only messages matching a message selector.</p>
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<p>
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The example will send 2 messages on a queue, use a QueueBrowser to browse
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the queue (looking at the message without removing them) and finally consume the 2 messages
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</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();</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 look up the JMS connection factory object from JNDI</li>
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<pre class="prettyprint">
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<code>ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");</code>
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</pre>
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<li>We create a JMS connection</li>
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<pre class="prettyprint">
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<code>connection = cf.createConnection();</code>
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</pre>
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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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<pre class="prettyprint">
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<code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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</pre>
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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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<pre class="prettyprint">
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<code>MessageProducer messageProducer = session.createProducer(topic);</code>
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</pre>
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<li>We create 2 JMS text messages that we are going to send.</li>
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<pre class="prettyprint">
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<code> TextMessage message_1 = session.createTextMessage("this is the 1st message");
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TextMessage message_2 = session.createTextMessage("this is the 2nd message");</code>
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</pre>
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<li>We send messages to the queue</li>
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<pre class="prettyprint">
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<code>messageProducer.send(message_1);
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messageProducer.send(message_2);</code>
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</pre>
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<li>We create a JMS QueueBrowser.<br />
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We have not specified a message selector so the browser will enumerate the entire content of the queue.
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</li>
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<pre class="prettyprint">
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<code>QueueBrowser browser = session.createBrowser(queue);</code>
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</pre>
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<li>We browse the queue and display all the messages' text
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</li>
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<pre class="prettyprint">
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<code>Enumeration messageEnum = browser.getEnumeration();
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while (messageEnum.hasMoreElements())
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{
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TextMessage message = (TextMessage)messageEnum.nextElement();
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System.out.println("Browsing: " + message.getText());
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}</code>
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</pre>
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<li>We close the browser once we have finished to use it</li>
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<pre class="prettyprint">
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<code>browser.close();</code>
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</pre>
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<p>The messages were browsed but they were not removed from the queue. We will now consume them.</p>
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<li>We create a JMS Message Consumer to receive the messages.</li>
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<pre class="prettyprint">
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<code>MessageConsumer messageConsumer = session.createConsumer(queue);</code>
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</pre>
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<li>We start the connection. In order for delivery to occur on any consumers or subscribers on a connection, the connection must be started</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>The 2 messages arrive at the consumer</li>
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<pre class="prettyprint">
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<code>TextMessage messageReceived = (TextMessage)messageConsumer.receive(5000);
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System.out.println("Received message: " + messageReceived.getText());
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messageReceived = (TextMessage)messageConsumer.receive(5000);
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System.out.println("Received message: " + messageReceived.getText());</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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