mbean-exporter.xml

<bean id="queueSizeExporter" class="org.springframework.jmx.export.MBeanExporter">
  <property name="beans">
    <map>
      <entry key="Mule.${app.name}:category=custom,name=queueSize" value-ref="mbeanQueueSizeAttributeQuery" />
    </map>
  </property>
</bean>

task-scheduler.xml

<task:scheduler id="mbeanQueueSizeUpdaterScheduler" pool-size="2" />
 
<task:scheduled-tasks scheduler="mbeanQueueSizeUpdaterScheduler">
  <task:scheduled ref="mbeanQueueSizeAttributeQuery" method="retrieveMbeanAttribute" fixed-delay="10000"/>
</task:scheduled-tasks>

mbean-attribute-config.xml

<bean id="mbeanQueueSizeAttributeQuery" class="com.mulesoft.monitor.jmx.MBeanAttributeQuery" init-method="initialise" destroy-method="destroy">
  <property name="jmxUrl" value="service:jmx:rmi:///jndi/rmi://${jms.ip}:${jms.jmxPort}/jmxrmi" />
  <property name="objectName" value="org.apache.activemq:BrokerName=localhost,Type=Queue,Destination=${jms.queueName}" />
  <property name="attribute" value="QueueSize" />
</bean>

MBeanAttributeQuery.java

public class MBeanAttributeQuery implements NotificationListener
{
 
  private String jmxUrl;
  private String objectName;
  private String attribute;
   
  protected JMXConnector jmxConnector;
  protected MBeanServerConnection mbeanServer;
  protected ObjectName objectNameExpression;
   
  protected boolean connectionClosed = true;
   
  private Object value;
  private String stringValue;
   
  protected Log logger = LogFactory.getLog(getClass());
   
  protected void checkConnection() throws IOException
  {
    //only connect if the jmxUrl is set and the connection is closed
    if ((jmxUrl != null) && connectionClosed)
    {
      try
      {
        //create a JMX connection and retrieve an mbean server connection
        JMXServiceURL url = new JMXServiceURL(jmxUrl);
        jmxConnector = JMXConnectorFactory.connect(url, null);
        mbeanServer = jmxConnector.getMBeanServerConnection();
     
        try
        {
          //try to remove the listener, this is necessary in case a connection was already established
          //and a listener already added. Avoiding adding listener twice
          jmxConnector.removeConnectionNotificationListener(this, null, null);
        }
        catch (ListenerNotFoundException e)
        {
          // ignore exception
        }
     
        //add this class as a connection notification listener
        jmxConnector.addConnectionNotificationListener(this, null, null);
        //since we managed to connect, set connectionClosed to false
        connectionClosed = false;
      }
      catch (IOException exception)
      {
        logger.error("Could not connect to JMX server " + jmxUrl + ", will retry on the next poll.", exception);
      }
    }
  }
   
  public void initialise() throws IOException, MalformedObjectNameException, NullPointerException
  {
    // if jmxUrl is not null, use it to connect
    checkConnection();
    // if jmxUrl is null, connect to the local mbean server
    if (jmxUrl == null)
    {
      mbeanServer = ManagementFactory.getPlatformMBeanServer();
    }
     
    objectNameExpression = new ObjectName(objectName);
  }
   
  public void destroy() throws IOException
  {
    if (jmxConnector != null)
    {
      jmxConnector.close();
    }
  }
   
  public void retrieveMbeanAttribute()
  throws MalformedObjectNameException, NullPointerException, InstanceNotFoundException,
  IntrospectionException, ReflectionException, AttributeNotFoundException, MBeanException, IOException
  {
    checkConnection();
    value = mbeanServer.getAttribute(objectNameExpression, attribute);
    stringValue = value.toString();
     
    logger.debug("Value collected = " + stringValue);
  }
   
   
  /**
  * if we receive a notification that the connection is closed, set the
  * connectionClosed to true in order to reconnect on the next poll
  */
  @Override
  public void handleNotification(Notification notification, Object handback)
  {
    if ("jmx.remote.connection.closed".equals(notification.getType()))
    {
      connectionClosed = true;
    }
  }
}