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10 KiB
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209 lines
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<html>
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<head>
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<title>ActiveMQ Management 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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</head>
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<body onload="prettyPrint()">
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<h1>Management Example</h1>
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<p>This example shows how to manage ActiveMQ using JMS Messages to invoke management operations on the server.</a></p>
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<p>To manage ActiveMQ using JMX, see the <a href="../jmx/readme.html">JMX</a> example.</p>
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<h2>Example configuration</h2>
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<p>ActiveMQ can be managed by sending JMS messages with specific properties to its <em>management</em> queue.</p>
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</p>By default, the management name is called <code>activemq.management</code> but this can be configured in <a href="server0/activemq-configuration.xml">activemq-configuration.xml</a>
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<pre class="prettyprint">
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<code><management-address>activemq.management</management-address></code>
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</pre>
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<p>The management queue requires a "special" user permission <code>manage</code> to be able to receive management messages.
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This is also configured in <a href="server0/activemq-configuration.xml">activemq-configuration.xml</a></p>
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<pre class="prettyprint">
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<code><security-setting match="activemq.management">
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<permission type="manage" roles="guest" />
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</security-setting></code>
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</pre>
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<h2>Example step-by-step</h2>
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<p><em>To run the example, simply type <code>mvn verify -Pexample</code> from this directory</em></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 its properties from <a href="server0/client-jndi.properties">client-jndi.properties</a></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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<p><em>Now that we have a message in the queue, we will manage the queue by retrieving the number of messages in the queue
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(i.e. 1) and by removing the message which has been sent in step 8.</em></p>
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<li>We create the JMS management queue. This is a <em>special</em> queue which is not looked up from JNDI but instantiated directly</li>
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<pre class="prettyprint">
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<code>Queue managementQueue = new ActiveMQQueue("activemq.management", "activemq.management");</code>
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</pre>
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<li>We create a <code>QueueRequestor</code> to send messages to the management queue and receive replies (see <a href="../queue-requestor/readme.html">queue-requestor example</a>)</li>
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<pre class="prettyprint">
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<code>QueueRequestor requestor = new QueueRequestor(session, managementQueue);</code>
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</pre>
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<li>We start the connection to receive replies on the requestor</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 create a JMS message which will be used as a <em>management</em> message</li>
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<pre class="prettyprint">
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<code>Message m = session.createMessage();</code>
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</pre>
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<li>a <em>management</em> message has well-defined properties that ActiveMQ server needs to know to perform management operations.<br />
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We use a helper class <code>JMSManagementHelper</code> to fill these properties:
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<ul>
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<li>The name of the resource to manage <code>jms.queue.exampleQueue</code>
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(i.e. <code>jms.queue</code> followed by the name of the queue as defined in <a href="server0/activemq-jms.xml">activemq-jms.xml</a>)</li>
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<li>In our case, the name of the attribute to retrieve <code>MessageCount</code></li>
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</ul>
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</li>
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<pre class="prettyprint">
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<code>JMSManagementHelper.putAttribute(m, "jms.queue.exampleQueue", "MessageCount");</code>
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</pre>
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<li>We send the <em>management</em> message using the requestor and wait for a reply</li>
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<pre class="prettyprint">
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<code>Message reply = requestor.request(m);</code>
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</pre>
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<li>We use a helper class <code>JMSManagementHelper</code> to retrieve the result from the reply message:
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<pre class="prettyprint">
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<code>int messageCount = (Integer)JMSManagementHelper.getResult(reply);
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System.out.println(queue.getQueueName() + " contains " + messageCount + " messages");</code>
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</pre>
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<li>We create another JMS message to use as a management message</li>
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<pre class="prettyprint">
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<code>m = session.createMessage();</code>
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</pre>
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<li>This time, we fill the <em>management</em> message with properties to <em>invoke</em> a management operation on the queue
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<ul>
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<li>the name of the resource <code>jms.queue.exampleQueue</code></li>
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<li>the name of the management operation <code>removeMessage</code></li>
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<li>any parameters required to invoke the management operations (in our case, the JMS Message ID of the message sent in step 8)</li>
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</ul>
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</li>
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<pre class="prettyprint">
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<code>JMSManagementHelper.putOperationInvocation(m, "jms.queue.exampleQueue", "removeMessage", message.getJMSMessageID());</code>
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</pre>
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<li>Again, we use the requestor to send the management message and wait for a reply</li>
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<pre class="prettyprint">
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<code>reply = requestor.request(m);</code>
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</pre>
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<li>We use the helper class to check that the operation was successfully invoked on the server</li>
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<pre class="prettyprint">
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<code>boolean success = JMSManagementHelper.hasOperationSucceeded(reply);
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System.out.println("operation invocation has succeeded: " + success);</code>
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</pre>
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<li>We use a helper class <code>JMSManagementHelper</code> to retrieve the result from the reply message:
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(in our case, the <code>removeMessage</code> method returns a boolean)</li>
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<pre class="prettyprint">
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<code>boolean messageRemoved = (Boolean)JMSManagementHelper.getResult(reply);
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System.out.println("message has been removed: " + messageRemoved);</code>
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</pre>
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<p><em>We will now consume the message from the queue but there will be none: the message sent at step 8 was removed by the management operation</em></p>
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<li>We create a JMS message consumer on the queue</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 try to receive a message from the queue. Since there is none, the call will timeout after 5000ms and messageReceived will be null
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</li>
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<pre class="prettyprint">
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<code>TextMessage messageReceived = (TextMessage) messageConsumer.receive(5000);
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System.out.println("Received message: " + messageReceived);</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#management.jms">Using Management Via JMS chapter</a></li>
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</ul>
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</body>
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</html>
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