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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>
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<code>InitialContext initialContext = getContext();</code>
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<li>We look-up the JMS topic object from JNDI</li>
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<code>Topic topic = (Topic) initialContext.lookup("/topic/exampleTopic");</code>
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<li>We look-up the JMS connection factory object from JNDI</li>
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<code>ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");</code>
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<li>We create a JMS connection</li>
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<code>connection = cf.createConnection();</code>
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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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<code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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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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<code>MessageProducer messageProducer = session.createProducer(topic);</code>
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<li>We create a JMS Message Consumer, messageConsumer1, to receive the message.</li>
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<code>MessageConsumer messageConsumer = session.createConsumer(topic);</code>
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<li>We create a JMS Message Consumer, messageConsumer2, to also receive the message.</li>
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<code>MessageConsumer messageConsumer2 = session.createConsumer(topic);</code>
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<li>We create a JMS text message that we are going to send.</li>
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<code>TextMessage message = session.createTextMessage("This is a text message");</code>
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<li>We send message to the topic</li>
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<code>messageProducer.send(message);</code>
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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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<code>connection.start();</code>
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<li>The message arrives at the first consumer</li>
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<code>TextMessage messageReceived = (TextMessage) messageConsumer1.receive();</code>
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<li>The message arrives at the second consumer</li>
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<code>messageReceived = (TextMessage) messageConsumer2.receive();</code>
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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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<code>finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}</code>
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