activemq-artemis/examples/jms/topic
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readme.html

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    <title>ActiveMQ JMS Topic Example</title>
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     <h1>JMS Topic Example</h1>

     <p>This example shows you how to send and receive a message to a JMS Topic with ActiveMQ.</p>
     <p>Topics are a standard part of JMS, please consult the JMS 1.1 specification for full details.</p>
     <p>A Topic is used to send messages using the publish-subscribe model, from a producer to 1 or more consumers.</p>

     <h2>Example step-by-step</h2>
     <p><i>To run the example, simply type <code>mvn verify -Pexample</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 topic object from JNDI</li>
        <pre class="prettyprint">
           <code>Topic topic = (Topic) initialContext.lookup("/topic/exampleTopic");</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 connection</li>
        <pre class="prettyprint">
           <code>connection = cf.createConnection();</code>
        </pre>

        <li>We create a JMS session. The session is created as non transacted and will auto acknowledge messages.</li>
        <pre class="prettyprint">
           <code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
        </pre>

        <li>We create a JMS message producer on the session. This will be used to send the messages.</li>
        <pre class="prettyprint">
          <code>MessageProducer messageProducer = session.createProducer(topic);</code>
       </pre>

        <li>We create a JMS Message Consumer, messageConsumer1, to receive the message.</li>
         <pre class="prettyprint">
           <code>MessageConsumer messageConsumer = session.createConsumer(topic);</code>
         </pre>

        <li>We create a JMS Message Consumer, messageConsumer2, to also receive the message.</li>
        <pre class="prettyprint">
          <code>MessageConsumer messageConsumer2 = session.createConsumer(topic);</code>
        </pre>

        <li>We create a JMS text message that we are going to send.</li>
        <pre class="prettyprint">
           <code>TextMessage message = session.createTextMessage("This is a text message");</code>
        </pre>

        <li>We send message to the topic</li>
        <pre class="prettyprint">
           <code>messageProducer.send(message);</code>
        </pre>

        <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>
        <pre class="prettyprint">
           <code>connection.start();</code>
        </pre>

        <li>The message arrives at the first consumer</li>
        <pre class="prettyprint">
           <code>TextMessage messageReceived = (TextMessage) messageConsumer1.receive();</code>
        </pre>

        <li>The message arrives at the second consumer</li>
        <pre class="prettyprint">
           <code>messageReceived = (TextMessage) messageConsumer2.receive();</code>
        </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">
           <code>finally
           {
              if (initialContext != null)
              {
                initialContext.close();
              }
              if (connection != null)
              {
                 connection.close();
              }
           }</code>
        </pre>



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