activemq-artemis/examples/jms/jms-auto-closeable
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readme.html

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  <head>
    <title>ActiveMQ JMS Auto Closable Example</title>
    <link rel="stylesheet" type="text/css" href="../common/common.css" />
    <link rel="stylesheet" type="text/css" href="../common/prettify.css" />
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     <h1>JMS Auto Closable Example</h1>

     <p>This example shows you how JMS resources, such as connections, sessions and consumers, in JMS 2 can be automatically closed on error.</p>
     <p>In this instance we auto close a connection after a subsequent call to a JMS producer send fails</p>

     <h2>Example step-by-step</h2>
     <p><i>To run the example, simply type <code>mvn verify</code> from this directory</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>client-jndi.properties</code> file in the directory <code>../common/config</code></li>
        <pre class="prettyprint">
           <code>InitialContext initialContext = getContext();</code>
        </pre>

        <li>We look-up the JMS queue object from JNDI</li>
        <pre class="prettyprint">
           <code>Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");</code>
        </pre>

        <li>We look-up the JMS connection factory object from JNDI</li>
        <pre class="prettyprint">
           <code>ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");</code>
        </pre>

        <li>We create a JMS context but we do it inside the try-with-resources statement like so:</li>
        <pre class="prettyprint">
           <code>
            try
            (
               JMSContext jmsContext = cf.createContext()
            )
           </code>
        </pre>

        <li>Inside the following try block we first create the producer</li>
        <pre class="prettyprint">
           <code>JMSProducer jmsProducer = jmsContext.createProducer();</code>
        </pre>

        <li>We then try to send a message. It is this call that throws an exception as the producer doesn't have the privileges
        to send a message</li>
        <pre class="prettyprint">
          <code>jmsProducer.send(queue, "this message will fail security!");</code>
       </pre>

        <li>We catch the exception from the send message and can do what we want, however the JMSContext will have been closed
        prior to entering the catch block.</li>
        <pre class="prettyprint">
           <code>System.out.println("expected exception from jmsProducer.send: " + e.getMessage());</code>
        </pre>

        <li>And finally, we close the Initial Context, note we no longer have to worry about clearing up the JMSContext.</li>

        <pre class="prettyprint">
           <code>finally
           {
              if (initialContext != null)
              {
                 initialContext.close();
              }
           }</code>
        </pre>



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