132 lines
6.0 KiB
HTML
132 lines
6.0 KiB
HTML
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<html>
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<head>
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<title>HornetQ Message Group 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>Message Group Example</h1>
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<p>This example shows you how to configure and use message groups with HornetQ.</p>
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<p>Message groups are sets of messages that has the following characteristics: </p>
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<li>Messages in a message group share the same group id, i.e. they have same JMSXGroupID string property values.</li>
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<li>Messages in a message group will be all delivered to no more than one of the queue's consumers. The consumer that receives the
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first message of a group will receive all the messages that belong to the group.</li>
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<p>You can make any message belong to a message group by setting its 'JMXGroupID' string property to the group id.
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In this example we create a message group 'Group-0'. And make such a message group of 10 messages. It also create two consumers on the queue
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where the 10 'Group-0' group messages are to be sent. You can see that with message grouping enabled, all the 10 messages will be received by
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the first consumer. The second consumer will receive none. </p>
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<p>Alternatively, HornetQ's connection factories can be configured to <em>auto group</em> messages. By setting <code>autogroup</code> to </code>true</code> on the <code>HornetQConnectionFactory</code>
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(or setting <code><autogroup>true</autogroup></code> in <code>hornetq-jms.xml</code>'s connection factory settings), a random unique id
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will be picked to create a message group. <em>Every messages</em> sent by a producer created from this connection factory will automatically
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be part of this message group.</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 connection</li>
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<pre class="prettyprint">
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<code>connection = cf.createConnection();</code>
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</pre>
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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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<pre class="prettyprint">
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<code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
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</pre>
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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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<pre class="prettyprint">
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<code>MessageProducer messageProducer = session.createProducer(topic);</code>
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</pre>
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<li>We create two consumers.</li>
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<pre class="prettyprint">
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<code>
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MessageConsumer consumer1 = session.createConsumer(queue);
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consumer1.setMessageListener(new SimpleMessageListener("consumer-1"));
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MessageConsumer consumer2 = session.createConsumer(queue);
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consumer2.setMessageListener(new SimpleMessageListener("consumer-2"));
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</code>
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</pre>
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<li>We create and send 10 text messages with group id 'Group-0'</li>
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<pre class="prettyprint">
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<code>
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int msgCount = 10;
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TextMessage[] groupMessages = new TextMessage[msgCount];
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for (int i = 0; i < msgCount; i++)
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{
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groupMessages[i] = session.createTextMessage("Group-0 message " + i);
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groupMessages[i].setStringProperty("JMSXGroupID", "Group-0");
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producer.send(groupMessages[i]);
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System.out.println("Sent message: " + groupMessages[i].getText());
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}
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</code>
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</pre>
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<li>We start the connection.</li>
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<pre class="prettyprint">
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<code>connection.start();</code>
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</pre>
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<li>We check the group messages are received by only one consumer</li>
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<pre class="prettyprint">
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<code>
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String trueReceiver = messageReceiverMap.get(groupMessages[0].getText());
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for (TextMessage grpMsg : groupMessages)
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{
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String receiver = messageReceiverMap.get(grpMsg.getText());
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if (!trueReceiver.equals(receiver))
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{
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System.out.println("Group message [" + grpMsg.getText() + "[ went to wrong receiver: " + receiver);
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result = false;
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}
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}
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</code>
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</pre>
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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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<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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if (connection != null)
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{
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connection.close();
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}
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}</code>
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</pre>
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</ol>
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<h2>More information</h2>
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<ul>
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<li>User Manual's <a href="../../../docs/user-manual/en/html_single/index.html#message-grouping">Message Grouping chapter</a></li>
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</ul>
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</body>
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</html>
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