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 JBoss AS 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);
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());
}
}
}
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.
