177 lines
7.5 KiB
HTML
177 lines
7.5 KiB
HTML
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<html>
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<head>
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<title>ActiveMQ JMS Interceptor 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>JMS Interceptor Example</h1>
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<p>This example shows you how to implement and configure a simple incoming, server-side interceptor with ActiveMQ.</p>
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<p>ActiveMQ allows an application to use an interceptor to hook into the messaging system. All that needs to do is to implement the
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Interceptor interface, as defined below: </p>
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<pre class="prettyprint">
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<code>
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public interface Interceptor
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{
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boolean intercept(Packet packet, RemotingConnection connection) throws ActiveMQException;
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}
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</code>
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</pre>
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<p>Once you have your own interceptor class, add it to the activemq-configuration.xml, as follows:</p>
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<pre class="prettyprint">
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<code>
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<configuration>
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...
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<remoting-incoming-interceptors>
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<class-name>org.apache.activemq.jms.example.SimpleInterceptor</class-name>
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</remoting-incoming-interceptors>
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...
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</configuration>
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</code>
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</pre>
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<p>With interceptor, you can handle various events in message processing. In this example, a simple interceptor, SimpleInterceptor, is implemented and configured.
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When the example is running, the interceptor will print out each events that are passed in the interceptor. And it will add a string property to the message being
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delivered. You can see that after the message is received, there will be a new string property appears in the received message.</p>
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<p>With our interceptor we always return <code>true</code> from the <code>intercept</code> method. If we were
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to return <code>false</code> that signifies that no more interceptors are to run or the target
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is not to be called. Return <code>false</code> to abort processing of the packet.</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 -Pexample</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(0);</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 a JMS text message that we are going to send.</li>
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<pre class="prettyprint">
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<code>TextMessage message = session.createTextMessage("This is a text message");</code>
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</pre>
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<li>We send message to the queue</li>
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<pre class="prettyprint">
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<code>messageProducer.send(message);</code>
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</pre>
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<li>We create a JMS Message Consumer to receive the message.</li>
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<pre class="prettyprint">
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<code>MessageConsumer messageConsumer = session.createConsumer(queue);</code>
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</pre>
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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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<pre class="prettyprint">
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<code>connection.start();</code>
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</pre>
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<li>The message arrives at the consumer. In this case we use a timeout of 5000 milliseconds but we could use a blocking 'receive()'</li>
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<pre class="prettyprint">
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<code>TextMessage messageReceived = (TextMessage) messageConsumer.receive(5000);</code>
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</pre>
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<li>We print out the message and the new property that has been added by the interceptor</li>
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<pre class="prettyprint">
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<code>System.out.println("Received message [" + messageReceived.getText() + "] with String property: " + messageReceived.getStringProperty("newproperty"));</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>
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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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}
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</code>
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</pre>
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</ol>
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<ol>
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<li>The SimpleInterceptor:</li>
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<pre class="prettyprint">
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<code>
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public class SimpleInterceptor implements Interceptor
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{
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public boolean intercept(Packet packet, RemotingConnection connection) throws ActiveMQException
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{
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System.out.println("SimpleInterceptor gets called!");
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System.out.println("Packet: " + packet.getClass().getName());
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System.out.println("RemotingConnection: " + connection.getRemoteAddress());
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if (packet instanceof SessionSendMessage)
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{
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SessionSendMessage realPacket = (SessionSendMessage)packet;
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Message msg = realPacket.getServerMessage();
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msg.putStringProperty(new SimpleString("newproperty"), new SimpleString("Hello from interceptor!"));
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}
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return true;
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}
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}
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</code>
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</pre>
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</ol>
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</body>
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</html>
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