To further enhance your control over the management of an application, JMX provides Monitor MBeans that allow you to observe attribute values as they vary over time and to fire notifications when these values exceed specific thresholds.
Monitor MBeans monitor attributes in other MBeans at specified intervals and derive a value from this observation called the derived gauge. The derived gauge is either the exact value of the attribute, or optionally the difference between two consecutive observed values of a numeric attribute. Depending on the Monitor MBean and its setup, it then can emit an MBean Notification. Monitors can also send notifications when error cases are encountered during monitoring.
Monitors are MBeans as well, and so can be created or destroyed dynamically. Typically, Monitor MBeans are used in combination with the statistics captured by the Runtime MBeans. For example, you could write an MBean to monitor the connection delay time of connections in a JDBC connection pool, or the number of messages dropped in a JMS destination. The Monitor MBean could then send a notification when certain thresholds are crossed. This gives you the opportunity to listen for those notifications and take some appropriate action.
There are three types of Monitor MBeans, each explained in depth in the JMX specification:
This can observe Integer attributes that behave like a counter. That is, the attribute value is always greater than or equal ...