| <div class="docbook"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">4.2. Publish/subscribe example</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="JMS-Client-0-8-Examples.html">Prev</a> </td><th align="center" width="60%">Chapter 4. Examples</th><td align="right" width="20%"> <a accesskey="n" href="JMS-Client-0-8-Client-Understanding.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="JMS-Client-0-8-Examples-PubSub"></a>4.2. Publish/subscribe example</h2></div></div></div><p>In this second example, we illustrate publish/subscribe messaging. Again, we create a |
| JNDI context using a properties file, use the context to lookup a connection factory, |
| create and start a connection, create a session, and lookup a destination (a topic) from |
| the JNDI context. Then we create a producer and two durable subscribers , send a message |
| with the producer. Both subscribers receive the same message.</p><div class="example"><a id="JMS-Client-0-8-Examples-PubSub-Java"></a><p class="title"><strong>Example 4.3. JMS Example - Publish/subscribe Messaging</strong></p><div class="example-contents"><pre class="programlisting"> |
| import javax.jms.*; |
| import javax.naming.Context; |
| import javax.naming.InitialContext; |
| |
| import java.util.Properties; |
| |
| public class StocksExample { |
| |
| public StocksExample() { |
| } |
| |
| public static void main(String[] args) throws Exception { |
| StocksExample stocks = new StocksExample(); |
| stocks.runTest(); |
| } |
| |
| private void runTest() throws Exception { |
| Properties properties = new Properties(); |
| properties.load(this.getClass().getResourceAsStream("stocks.properties")); |
| Context context = new InitialContext(properties); |
| |
| ConnectionFactory connectionFactory |
| = (ConnectionFactory) context.lookup("qpidConnectionFactory"); |
| Connection connection = connectionFactory.createConnection(); |
| connection.start(); |
| |
| Session session = connection.createSession(true, Session.SESSION_TRANSACTED); |
| Topic priceTopic = (Topic) context.lookup("myprices"); <a class="co" href="JMS-Client-0-8-Examples-PubSub.html#callout-pubsub-destination" id="pubsub-java-destination"><span><img alt="1" border="0" src="images/callouts/1.png" /></span></a> |
| |
| MessageConsumer subscriber1 = session.createDurableSubscriber(priceTopic, "sub1"); <a class="co" href="JMS-Client-0-8-Examples-PubSub.html#callout-pubsub-subscribers" id="pubsub-java-subscribers"><span><img alt="2" border="0" src="images/callouts/2.png" /></span></a> |
| MessageConsumer subscriber2 = session.createDurableSubscriber(priceTopic, "sub2" /*, "price > 150", false*/ ); |
| MessageProducer messageProducer = session.createProducer(priceTopic); |
| |
| Message message = session.createMessage(); |
| message.setStringProperty("instrument", "IBM"); |
| message.setIntProperty("price", 100); |
| messageProducer.send(message); |
| session.commit(); |
| |
| message = subscriber1.receive(1000); |
| session.commit(); |
| System.out.println("Subscriber 1 received : " + message); |
| |
| message = subscriber2.receive(1000); |
| session.commit(); |
| System.out.println("Subscriber 2 received : " + message); |
| |
| session.unsubscribe("sub1"); <a class="co" href="JMS-Client-0-8-Examples-PubSub.html#callout-pubsub-unsubscribe" id="pubsub-java-unsubscribe"><span><img alt="3" border="0" src="images/callouts/3.png" /></span></a> |
| session.unsubscribe("sub2"); |
| connection.close(); |
| context.close(); |
| } |
| } |
| </pre></div></div><br class="example-break" /><div class="calloutlist"><table border="0" summary="Callout list"><tr><td align="left" valign="top" width="5%"><p><a id="callout-pubsub-destination"></a><a href="#pubsub-java-destination"><span><img alt="1" border="0" src="images/callouts/1.png" /></span></a> </p></td><td align="left" valign="top"><p>Looks up a destination for the topic with JNDI name myprices.</p></td></tr><tr><td align="left" valign="top" width="5%"><p><a id="callout-pubsub-subscribers"></a><a href="#pubsub-java-subscribers"><span><img alt="2" border="0" src="images/callouts/2.png" /></span></a> </p></td><td align="left" valign="top"><p>Creates two durable subscribers, <code class="literal">sub1</code> and |
| <code class="literal">sub2</code>. Durable subscriptions retain messages for the |
| client even when the client is disconnected, until the subscription is |
| unsubscribed. Subscription 2 has a (commented out) message selector argument so |
| you can conveniently experiement with the effect of those. <a class="footnote" href="#ftn.d0e283" id="d0e283"><sup class="footnote">[3]</sup></a></p></td></tr><tr><td align="left" valign="top" width="5%"><p><a id="callout-pubsub-unsubscribe"></a><a href="#pubsub-java-unsubscribe"><span><img alt="3" border="0" src="images/callouts/3.png" /></span></a> </p></td><td align="left" valign="top"><p>Unsubscribes the two durable subscribers, permanently removing the knowledge |
| of the subscriptions from the system. An application would normally |
| <span class="emphasis"><em>NOT</em></span> do this. The typical use-case for durable |
| subsciption is one where the subscription exists over an extended period of |
| time.</p></td></tr></table></div><p>The contents of the <code class="literal">stocks.properties</code> file are shown below.</p><div class="example"><a id="JMS-Client-0-8-Examples-PubSub-PropertiesFile"></a><p class="title"><strong>Example 4.4. JMS Example - Publish/subscribe Messaging - JNDI Properties</strong></p><div class="example-contents"><pre class="programlisting"> |
| java.naming.factory.initial = org.apache.qpid.jndi.PropertiesFileInitialContextFactory |
| connectionfactory.qpidConnectionFactory = amqp://guest:guest@clientid/?brokerlist='tcp://localhost:5672' |
| topic.myprices = prices <a class="co" href="JMS-Client-0-8-Examples-PubSub.html#callout-pubsub-properties-destination" id="pubsub-properties-destination"><span><img alt="1" border="0" src="images/callouts/1.png" /></span></a> |
| </pre></div></div><br class="example-break" /><div class="calloutlist"><table border="0" summary="Callout list"><tr><td align="left" valign="top" width="5%"><p><a id="callout-pubsub-properties-destination"></a><a href="#pubsub-properties-destination"><span><img alt="1" border="0" src="images/callouts/1.png" /></span></a> </p></td><td align="left" valign="top"><p>Defines a topic for which MessageProducers and/or MessageConsumers send and |
| receive messages. The format of this entry is described in <a class="xref" href="JMS-Client-0-8-JNDI-Properties-Format-Topic.html" title="6.3. Topic">Section 6.3, “Topic”</a>.</p></td></tr></table></div><div class="footnotes"><br /><hr style="width:100; text-align:left;margin-left: 0" /><div class="footnote" id="ftn.d0e283"><p><a class="para" href="#d0e283"><sup class="para">[3] </sup></a>Each durable subscription is implemented as a queue on the Broker. See |
| <a class="xref" href="JMS-Client-0-8-Client-Understanding-MessageConsumer.html#JMS-Client-0-8-Client-Understanding-MessageConsumer-TopicSubscriptions" title="5.6.2. Topic Subscriptions">Section 5.6.2, “Topic Subscriptions”</a> for details.</p></div></div></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="JMS-Client-0-8-Examples.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="JMS-Client-0-8-Examples.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="JMS-Client-0-8-Client-Understanding.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">Chapter 4. Examples </td><td align="center" width="20%"><a accesskey="h" href="JMS-Client-Book.html">Home</a></td><td align="right" valign="top" width="40%"> Chapter 5. Understanding the Client</td></tr></table></div></div> |
