194 lines
9.2 KiB
HTML
194 lines
9.2 KiB
HTML
<html>
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<title>ActiveMQ Management Notification 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>Management Notification Example</h1>
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<p>This example shows how to receive management notifications from ActiveMQ using JMS Messages.</p>
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<p>ActiveMQ servers emit management notifications when events of interest occur (consumers are created or closed,
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destinations are created or deleted, security authentication fails, etc.).<br />
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These notifications can be received either by using JMX (see <a href="../jmx/readme.html">JMX example</a>) or by receiving JMS Messages
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from a well-known destination.</p>
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<p>This example will setup a JMS MessageListener to receive management notifications. We will also perform normal JMS operations to see the kind
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of notifications they trigger.</p>
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<h2>Example configuration</h2>
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<p>ActiveMQ can configured to send JMS messages when management notifications are emitted on the server.</p>
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<p>By default, the management name is called <code>activemq.notifications</code> but this can be configured in <a href="server0/activemq-configuration.xml">activemq-configuration.xml</a>.
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For this example, we will set it to <code>jms.topic.notificationsTopic</code> to be able to receive notifications from a JMS Topic.</p>
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<pre class="prettyprint">
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<code><management-notification-address>jms.topic.notificationsTopic</management-notification-address></code>
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</pre>
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<p>Since we want to lookup the notifications topic using JNDI, we also declare it in <a href="server0/activemq-jms.xml">activemq-jms.xml</a>
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<pre class="prettyprint">
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<code><topic name="notificationsTopic">
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<entry name="/topic/notificationsTopic"/>
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</topic></code>
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</pre>
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<p>The notification queue requires permission to create/delete temporary queues and consume 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 for notification topic-->
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<security-setting match="jms.topic.notificationsTopic">
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<permission type="consume" roles="guest"/>
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<permission type="createNonDurableQueue" roles="guest"/>
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<permission type="deleteNonDurableQueue" 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</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, a session and a message producer for the example queue</li>
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<pre class="prettyprint">
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<code>connection = cf.createConnection();
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Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
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MessageProducer producer = session.createProducer(queue);</code>
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</pre>
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<li>We look up the JMS Topic used to receive the notifications from JNDI</li>
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<pre class="prettyprint">
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<code>Topic notificationsTopic = (Topic) initialContext.lookup("/topic/notificationsTopic");</code>
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</pre>
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<li>We create a MessageConsumer for the notification queue and set its MessageListener. When a notification is received, we will simply display all the message properties</li>
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<pre class="prettyprint">
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<code>MessageConsumer notificationConsumer = session.createConsumer(notificationsTopic);
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notificationConsumer.setMessageListener(new MessageListener()
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{
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public void onMessage(Message notif)
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{
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System.out.println("------------------------");
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System.out.println("Received notification:");
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try
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{
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Enumeration propertyNames = notif.getPropertyNames();
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while (propertyNames.hasMoreElements())
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{
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String propertyName = (String)propertyNames.nextElement();
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System.out.format(" %s: %s\n", propertyName, notif.getObjectProperty(propertyName));
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}
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}
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catch (JMSException e)
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{
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}
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System.out.println("------------------------");
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}
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});</code>
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</pre>
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<li>We start the connection to receive messages</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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<p><em>Now that a message listener is setup to receive management notifications, we will perform regular JMS operations to
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see what kind of notifications are triggered</em></p>
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<li>We create a JMS message consumer on the example queue</li>
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<pre class="prettyprint">
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<code>MessageConsumer consumer = session.createConsumer(queue);</code>
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</pre>
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<p>This will generate a <code>CONSUMER_CREATED</code> notification:
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<pre class="prettyprint">
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<code>------------------------
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Received notification:
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_HQ_RoutingName: jms.queue.exampleQueue
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_HQ_Address: jms.queue.exampleQueue
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...
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_HQ_ConsumerCount: 1
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...
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_HQ_NotifType: CONSUMER_CREATED
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------------------------</code>
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</pre>
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<p>The notification tells us that a consumer was created for the JMS queue <code>exampleQueue</code>. When the notification
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was emitted, this consumer was the only one for the queue</p>
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<li>We close this consumer</li>
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<pre class="prettyprint">
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<code>consumer.close();</code>
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</pre>
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<p>This will generate a <code>CONSUMER_CLOSED</code> notification:
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<pre class="prettyprint">
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<code>------------------------
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Received notification:
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_HQ_RoutingName: jms.queue.exampleQueue
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_HQ_Address: jms.queue.exampleQueue
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...
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_HQ_ConsumerCount: 0
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...
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_HQ_NotifType: CONSUMER_CLOSED
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------------------------</code>
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</pre>
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<p>The notification tells us that a consumer was closed for the JMS queue <code>exampleQueue</code>. When the notification
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was emitted, there were no other consumers on the queue</p>
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<li>As a last example, we will create a connection with invalid user credentials</li>
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<pre class="prettyprint">
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<code>try
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{
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cf.createConnection("not.a.valid.user", "not.a.valid.password");
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} catch (JMSException e)
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{
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}</code>
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</pre>
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<p>This will generate a <code>SECURITY_AUTHENTICATION_VIOLATION</code> notification:
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<pre class="prettyprint">
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<code>------------------------
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Received notification:
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_HQ_User: not.a.valid.user
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...
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_HQ_NotifType: SECURITY_AUTHENTICATION_VIOLATION
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------------------------
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</code>
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</pre>
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<p>The notification tells us that a user named <code>not.a.valid.user</code> failed to authenticate when creating a connection to ActiveMQ.</p>
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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.notifications">Management Notifications chapter</a></li>
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</ul>
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</body>
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</html> |