5.4.4. Receiving JMX Notifications

JBoss Cache users can register a listener to receive cache events described earlier in the Section 2.7, “ Adding a Cache Listener - registering for cache events ” chapter. Users can alternatively utilize the cache's management information infrastructure to receive these events via JMX notifications. Cache events are accessible as notifications by registering a NotificationListener for the CacheJmxWrapper.

See the section in the Section 13.2, “JMX MBean Notifications” pertaining to JMX notifications for a list of notifications that can be received through the CacheJmxWrapper.

The following is an example of how to programmatically receive cache notifications when running in a EAP environment. In this example, the client uses a filter to specify which events are of interest.

   MyListener listener = new MyListener();
   NotificationFilterSupport filter = null;

   // get reference to MBean server
   Context ic = new InitialContext();
   MBeanServerConnection server = (MBeanServerConnection)ic.lookup("jmx/invoker/RMIAdaptor");

   // get reference to CacheMgmtInterceptor MBean
   String cache_service = "jboss.cache:service=TomcatClusteringCache";
   ObjectName mgmt_name = new ObjectName(cache_service);

   // configure a filter to only receive node created and removed events
   filter = new NotificationFilterSupport();
   filter.disableAllTypes();
   filter.enableType(CacheNotificationBroadcaster.NOTIF_NODE_CREATED);
   filter.enableType(CacheNotificationBroadcaster.NOTIF_NODE_REMOVED);

   // register the listener with a filter
   // leave the filter null to receive all cache events
   server.addNotificationListener(mgmt_name, listener, filter, null);

   // ...

   // on completion of processing, unregister the listener
   server.removeNotificationListener(mgmt_name, listener, filter, null);

   MyListener listener = new MyListener();
   NotificationFilterSupport filter = null;

   // get reference to MBean server
   Context ic = new InitialContext();
   MBeanServerConnection server = (MBeanServerConnection)ic.lookup("jmx/invoker/RMIAdaptor");

   // get reference to CacheMgmtInterceptor MBean
   String cache_service = "jboss.cache:service=TomcatClusteringCache";
   ObjectName mgmt_name = new ObjectName(cache_service);

   // configure a filter to only receive node created and removed events
   filter = new NotificationFilterSupport();
   filter.disableAllTypes();
   filter.enableType(CacheNotificationBroadcaster.NOTIF_NODE_CREATED);
   filter.enableType(CacheNotificationBroadcaster.NOTIF_NODE_REMOVED);

   // register the listener with a filter
   // leave the filter null to receive all cache events
   server.addNotificationListener(mgmt_name, listener, filter, null);

   // ...

   // on completion of processing, unregister the listener
   server.removeNotificationListener(mgmt_name, listener, filter, null);

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The following is the simple notification listener implementation used in the previous example.

   private class MyListener implements NotificationListener, Serializable
   {
      public void handleNotification(Notification notification, Object handback)
      {
         String message = notification.getMessage();
         String type = notification.getType();
         Object userData = notification.getUserData();

         System.out.println(type + ": " + message);

         if (userData == null)
         {
            System.out.println("notification data is null");
         }
         else if (userData instanceof String)
         {
            System.out.println("notification data: " + (String) userData);
         }
         else if (userData instanceof Object[])
         {
            Object[] ud = (Object[]) userData;
            for (Object data : ud)
            {
               System.out.println("notification data: " + data.toString());
            }
         }
         else
         {
            System.out.println("notification data class: " + userData.getClass().getName());
         }
      }
   }

   private class MyListener implements NotificationListener, Serializable
   {
      public void handleNotification(Notification notification, Object handback)
      {
         String message = notification.getMessage();
         String type = notification.getType();
         Object userData = notification.getUserData();

         System.out.println(type + ": " + message);

         if (userData == null)
         {
            System.out.println("notification data is null");
         }
         else if (userData instanceof String)
         {
            System.out.println("notification data: " + (String) userData);
         }
         else if (userData instanceof Object[])
         {
            Object[] ud = (Object[]) userData;
            for (Object data : ud)
            {
               System.out.println("notification data: " + data.toString());
            }
         }
         else
         {
            System.out.println("notification data class: " + userData.getClass().getName());
         }
      }
   }

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Note that the JBoss Cache management implementation only listens to cache events after a client registers to receive MBean notifications. As soon as no clients are registered for notifications, the MBean will remove itself as a cache listener.

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5.4.4. Receiving JMX Notifications

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