"Building Manageability"
Vol. 9, Issue 11, p. 44

	



Listing 1: Connecting using MXBean Proxy

MBeanServerConnection mBeanServerConnection = null;
try{

mBeanServerConnection = 
                  JMXConnectorFactory.connect(
                  new JMXServiceURL(jmxServiceURL),null)
                        .getMBeanServerConnection();

MemoryMXBean memoryMXBean  =
               ManagementFactory.newPlatformMXBeanProxy(  
                        mBeanServerConnection,
                        ManagementFactory.MEMORY_MXBEAN_NAME,
                        MemoryMXBean.class);

} catch (Exception e) {
            System.err.println("Failed to Connect with "
                    + "JMXServiceURL '" + jmxServiceURL +
 "':  " + e);

}

Listing 2: Connecting directly to the MBeanServer

// get an instance of the logging MXBean
ObjectInstance loggingInstance =
                mBeanServerConnection.getObjectInstance(
               new ObjectName("java.util.logging:type=Logging"));

// Use the query mechanism to get all the MXBeans that are
//part of the java.lang domain.
Set mBeanSet =
          mBeanServerConnection.queryMBeans(
               new ObjectName("java.lang:*"), null);

Listing 3: Detecting deadlocked threads

// check if threads are deadlocked
long[] deadlockedThreadIds =threadMxBean.
     findMonitorDeadlockedThreads();
if (deadlockedThreadIds != null){
	for( long element:deadlockedThreadIds ){

//for each threaded get the ThreadInfo
		ThreadInfo tinfo =threadMxBean.getThreadInfo(element);

	// print information about the blocked thread
		System.out.println(" Blocked Thread Id is " + 
tinfo.getThreadId();
System.out.println("Thread ID of blocking thread is " + 
tinfo.getLockOwnerId();

}

}

Listing 4: Using the logging MXBean

LoggingMXBean logger  =
               ManagementFactory.newPlatformMXBeanProxy(
mBeanServerConnection,
LogManager.LOGGING_MXBEAN_NAME,
LoggingMXBean.class);
try{
  if (! logger.getLoggerLevel(loggerName).
equals(Level.INFO.getName()))
  {
  	logger.setLoggerLevel(loggerName,
                           Level.INFO.getName());
  }
} catch( IllegalArgumentException  e){
System.err.println("Logger does not exist " +
  loggerName);
}

Listing 5: Creating the ObjectPool class

public class ObjectPool implements ObjectPoolMBean {

public ObjectPool () {
	}


public Integer availableObjects() {
return (pool.getTotalCapacity -
pool.usedCapacity());
	}


public Integer availableObjects() {
	return pool.getTotalCapacity();	
	}

public String poolName() {
	return pool.name();
	}

}

Listing 6: Creating the LowMemory Listener

class LowMemoryListener implements NotificationListener {
	public void handleNotification(
			Notification notification,
			Object handback)  {
		String notifyType = notification.getType();
		if (notifyType.equals
	(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {

		// potential low memory condition
		// save the pending requests for processing later
		saveRequests( requestQueue.pending());

		// pause receiving new requests
		requestQueue.pauseNewRequests();
		}
	}
}

Listing 7: Using a polling-based mechanism to empty saved request queue

while (true) {
if (!pool.isUsageThresholdExceeded()) {
	if( !saveRequestQueue.isEmpty()) {
	// start restoring requests one by one
		restoreRequests(saveRequestQueue.getRequest());
	}else {

	//no more saved requests left
	// start receiving new requests
		requestQueue.startNewRequests();

	}

}


   try {
   	Thread.sleep(SLEEP_INTERVAL);
   } catch (InterruptedException e) {
   }
}