77 lines
3.0 KiB
HTML
77 lines
3.0 KiB
HTML
<html>
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<head>
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<title>ActiveMQ JMS Auto Closable 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 Auto Closable Example</h1>
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<p>This example shows you how JMS resources, such as connections, sessions and consumers, in JMS 2 can be automatically closed on error.</p>
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<p>In this instance we auto close a connection after a subsequent call to a JMS producer send fails</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 context but we do it inside the try-with-resources statement like so:</li>
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<pre class="prettyprint">
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<code>
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try
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(
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JMSContext jmsContext = cf.createContext()
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)
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</code>
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</pre>
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<li>Inside the following try block we first create the producer</li>
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<pre class="prettyprint">
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<code>JMSProducer jmsProducer = jmsContext.createProducer();</code>
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</pre>
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<li>We then try to send a message. It is this call that throws an exception as the producer doesn't have the privileges
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to send a message</li>
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<pre class="prettyprint">
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<code>jmsProducer.send(queue, "this message will fail security!");</code>
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</pre>
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<li>We catch the exception from the send message and can do what we want, however the JMSContext will have been closed
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prior to entering the catch block.</li>
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<pre class="prettyprint">
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<code>System.out.println("expected exception from jmsProducer.send: " + e.getMessage());</code>
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</pre>
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<li>And finally, we close the Initial Context, note we no longer have to worry about clearing up the JMSContext.</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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}</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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