activemq-artemis/examples/jms/management-notifications
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readme.html

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    <title>ActiveMQ Artemis Management Notification Example</title>
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     <h1>Management Notification Example</h1>
     <p>This example shows how to receive management notifications from ActiveMQ Artemis using JMS Messages.</p>
     <p>ActiveMQ Artemis servers emit management notifications when events of interest occur (consumers are created or closed,
         destinations are created or deleted, security authentication fails, etc.).<br />
         These notifications can be received either by using JMX (see <a href="../jmx/readme.html">JMX example</a>) or by receiving JMS Messages
         from a well-known destination.</p>
     <p>This example will setup a JMS MessageListener to receive management notifications. We will also perform normal JMS operations to see the kind
         of notifications they trigger.</p>
     
     <h2>Example configuration</h2>

     <p>ActiveMQ Artemis can configured to send JMS messages when management notifications are emitted on the server.</p>
     <p>By default, the management name is called <code>activemq.notifications</code> but this can be configured in <a href="server0/broker.xml">broker.xml</a>.
        For this example, we will set it to <code>jms.topic.notificationsTopic</code> to be able to receive notifications from a JMS Topic.</p>
      <pre class="prettyprint">
         <code>&lt;management-notification-address&gt;jms.topic.notificationsTopic&lt;/management-notification-address&gt;</code>
     </pre>
     
     <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>
     <pre class="prettyprint">
         <code>&lt;topic name="notificationsTopic"&gt;
            &lt;entry name="/topic/notificationsTopic"/&gt;
         &lt;/topic&gt;</code>
     </pre>
     <p>The notification queue requires permission to create/delete temporary queues and consume messages.
         This is also configured in <a href="server0/broker.xml">broker.xml</a></p>
     <pre class="prettyprint">
         <code><!--security for notification topic-->
         &lt;security-setting match="jms.topic.notificationsTopic"&gt;
            &lt;permission type="consume" roles="guest"/&gt;
            &lt;permission type="createNonDurableQueue" roles="guest"/&gt;
            &lt;permission type="deleteNonDurableQueue" roles="guest"/&gt;
         &lt;/security-setting&gt;</code>
     </pre>
     
     <h2>Example step-by-step</h2>
     <p><em>To run the example, simply type <code>mvn verify -Pexample</code> from this directory</em></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 its properties from <a href="server0/client-jndi.properties">client-jndi.properties</a></li>
        <pre class="prettyprint">
            <code>InitialContext initialContext = getContext(0);</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, a session and a message producer for the example queue</li>
        <pre class="prettyprint">
            <code>connection = cf.createConnection();
            Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
            MessageProducer producer = session.createProducer(queue);</code>
        </pre>
        
        <li>We look up the JMS Topic used to receive the notifications from JNDI</li>
        <pre class="prettyprint">
            <code>Topic notificationsTopic = (Topic) initialContext.lookup("/topic/notificationsTopic");</code>
        </pre>

        <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>
        <pre class="prettyprint">
           <code>MessageConsumer notificationConsumer = session.createConsumer(notificationsTopic);
           notificationConsumer.setMessageListener(new MessageListener()
           {
              public void onMessage(Message notif)
              {
                 System.out.println("------------------------");
                 System.out.println("Received notification:");
                 try
                 {
                    Enumeration propertyNames = notif.getPropertyNames();
                    while (propertyNames.hasMoreElements())
                    {
                       String propertyName = (String)propertyNames.nextElement();
                       System.out.format("  %s: %s\n", propertyName, notif.getObjectProperty(propertyName));
                    }
                 }
                 catch (JMSException e)
                 {
                 }
                 System.out.println("------------------------");
              }            
           });</code>
        </pre>
        
        <li>We start the connection to receive messages</li>
        <pre class="prettyprint">
            <code>connection.start();</code>
        </pre>
        
        <p><em>Now that a message listener is setup to receive management notifications, we will perform regular JMS operations to 
            see what kind of notifications are triggered</em></p>
            
        <li>We create a JMS message consumer on the example queue</li>
        <pre class="prettyprint">
            <code>MessageConsumer consumer = session.createConsumer(queue);</code>
        </pre>
        
        <p>This will generate a <code>CONSUMER_CREATED</code> notification:
        <pre class="prettyprint">
            <code>------------------------
            Received notification:
              _AMQ_RoutingName: jms.queue.exampleQueue
              _AMQ_Address: jms.queue.exampleQueue
              ...
              _AMQ_ConsumerCount: 1
              ...
              _AMQ_NotifType: CONSUMER_CREATED
            ------------------------</code>
        </pre>
        <p>The notification tells us that a consumer was created for the JMS queue <code>exampleQueue</code>. When the notification
            was emitted, this consumer was the only one for the queue</p>
            
        <li>We close this consumer</li>
        <pre class="prettyprint">
            <code>consumer.close();</code>
        </pre>

        <p>This will generate a <code>CONSUMER_CLOSED</code> notification:
        <pre class="prettyprint">
            <code>------------------------
            Received notification:
              _AMQ_RoutingName: jms.queue.exampleQueue
              _AMQ_Address: jms.queue.exampleQueue
              ...
              _AMQ_ConsumerCount: 0
              ...
              _AMQ_NotifType: CONSUMER_CLOSED
            ------------------------</code>
        </pre>
        <p>The notification tells us that a consumer was closed for the JMS queue <code>exampleQueue</code>. When the notification
            was emitted, there were no other consumers on the queue</p>

        <li>As a last example, we will create a connection with invalid user credentials</li>
        <pre class="prettyprint">
            <code>try
            {
               cf.createConnection("not.a.valid.user", "not.a.valid.password");
            } catch (JMSException e)
            {            
            }</code>
        </pre>
        
        <p>This will generate a <code>SECURITY_AUTHENTICATION_VIOLATION</code> notification:
        <pre class="prettyprint">
            <code>------------------------
            Received notification:
              _AMQ_User: not.a.valid.user
              ...
              _AMQ_NotifType: SECURITY_AUTHENTICATION_VIOLATION
            ------------------------
            </code>
        </pre>
        <p>The notification tells us that a user named <code>not.a.valid.user</code> failed to authenticate when creating a connection to ActiveMQ Artemis.</p>
        
        <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>
     
     <h2>More information</h2>
     
     <ul>
         <li>User Manual's <a href="../../../docs/user-manual/en/html_single/index.html#management.notifications">Management Notifications chapter</a></li>
     </ul>         

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