166 lines
7.5 KiB
HTML
166 lines
7.5 KiB
HTML
<!--
|
|
Licensed to the Apache Software Foundation (ASF) under one
|
|
or more contributor license agreements. See the NOTICE file
|
|
distributed with this work for additional information
|
|
regarding copyright ownership. The ASF licenses this file
|
|
to you under the Apache License, Version 2.0 (the
|
|
"License"); you may not use this file except in compliance
|
|
with the License. You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing,
|
|
software distributed under the License is distributed on an
|
|
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
|
|
KIND, either express or implied. See the License for the
|
|
specific language governing permissions and limitations
|
|
under the License.
|
|
-->
|
|
|
|
<html>
|
|
<head>
|
|
<title>ActiveMQ JMS Queue Selector Example</title>
|
|
<link rel="stylesheet" type="text/css" href="../common/common.css" />
|
|
<link rel="stylesheet" type="text/css" href="../common/prettify.css" />
|
|
<script type="text/javascript" src="../common/prettify.js"></script>
|
|
</head>
|
|
<body onload="prettyPrint()">
|
|
<h1>JMS Queue Selector Example</h1>
|
|
|
|
<p>This example shows you how to selectively consume messages using message selectors with queue consumers.</p>
|
|
|
|
<p>Message selectors are strings with special syntax that can be used in creating consumers. Message consumers
|
|
created with a message selector will only receive messages that match its selector. On message delivery, the JBoss Message
|
|
Server evaluates the corresponding message headers of the messages against each selector, if any, and then delivers
|
|
the 'matched' messages to its consumer. Please consult the JMS 1.1 specification for full details.</p>
|
|
|
|
<p>In this example, three message consumers are created on a queue. The first consumer is created with selector
|
|
<code>'color=red'</code>, it only receives messages that
|
|
have a 'color' string property of 'red' value; the second is created with selector <code>'color=green'</code>, it
|
|
only receives messages who have a 'color' string property of
|
|
'green' value; and the third without a selector, which means it receives all messages. To illustrate, three messages
|
|
with different 'color' property values are created and sent.</p>
|
|
|
|
<p>Selectors can be used with both queue consumers and topic consumers. The difference is that with queue consumers,
|
|
a message is only delivered to one consumer on the queue, while topic consumers the message will be delivered to every
|
|
matching consumers. In this example, if the third consumer (anyConsumer) were the first consumer created, it will
|
|
consume the first message delivered, therefore there is no chance for the next consumer to get the message, even if it
|
|
matches the selector.</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 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 connection</li>
|
|
<pre class="prettyprint">
|
|
<code>connection = cf.createConnection();</code>
|
|
</pre>
|
|
|
|
<li>We start the connection</li>
|
|
<pre class="prettyprint">
|
|
<code>connection.start();</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(queue);</code>
|
|
</pre>
|
|
|
|
<li>We create two selectors.</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
String redSelector = "color='red'";
|
|
String greenSelector = "color='green'";
|
|
</code>
|
|
</pre>
|
|
|
|
<li>We Create a JMS Message Consumer that receives 'red' messages.</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
MessageConsumer redConsumer = session.createConsumer(queue, redSelector);
|
|
redConsumer.setMessageListener(new SimpleMessageListener("red"));
|
|
</code>
|
|
</pre>
|
|
|
|
<li>We Create a second JMS Message Consumer that receives 'green' messages.</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
MessageConsumer greenConsumer = session.createConsumer(queue, greenSelector);
|
|
greenConsumer.setMessageListener(new SimpleMessageListener("green"));
|
|
</code>
|
|
</pre>
|
|
|
|
<li>We Create another JMS Message Consumer that receives all messages. Please not that the order
|
|
of consumers on a queue is of significance. If the anyConsumer is created before the above two, the
|
|
result will be totally different.</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
MessageConsumer anyConsumer = session.createConsumer(queue);
|
|
anyConsumer.setMessageListener(new SimpleMessageListener("any"));
|
|
</code>
|
|
</pre>
|
|
|
|
<li>We Create three messages, each has a different color property.</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
TextMessage redMessage = session.createTextMessage("Red");
|
|
redMessage.setStringProperty("color", "red");
|
|
TextMessage greenMessage = session.createTextMessage("Green");
|
|
greenMessage.setStringProperty("color", "green");
|
|
TextMessage blueMessage = session.createTextMessage("Blue");
|
|
blueMessage.setStringProperty("color", "blue");
|
|
</code>
|
|
</pre>
|
|
|
|
<li>We send the messages to the topic</li>
|
|
<pre class="prettyprint">
|
|
<code>
|
|
producer.send(redMessage);
|
|
System.out.println("Message sent: " + redMessage.getText());
|
|
producer.send(greenMessage);
|
|
System.out.println("Message sent: " + greenMessage.getText());
|
|
producer.send(blueMessage);
|
|
System.out.println("Message sent: " + blueMessage.getText());
|
|
</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>
|
|
</ol>
|
|
</body>
|
|
</html>
|