JMX

Java Management Extensions (JMX) is a Java technology that supplies tools for managing and monitoring applications, system objects, devices (e. g. printers) and service oriented networks. Those resources are represented by objects called MBeans (for Managed Bean). In the API, classes can be dynamically loaded and instantiated. Managing and monitoring applications can be designed and developed using the Java Dynamic Management Kit (JDMK) which is also available and more commonly implemented using the open sourced version OpenDMK.

JMX classes live in the javax.management packages.

JMX is a part of the Java platform since Java SE 5 (though some components are optional and not bundled with the JRE).

References

• JMX Technology Home
• JMX Technology Guide
• JMX Official Best Practices
• Java Monitoring and Management Technology Guide
• JMX's Wikipedia Entry
• JMX Reference API
• JMX Trail in the Java SE Tutorial
• JMDK's Wikipedia Entry
• The SO question JMX Defined

Glossary

• MBean: A logical unit, or service, most easily visualized as a Java Bean, that provides a defined service exposed through the JMX protocol. One instance of an MBean typically is identified by an ObjectName (see below). These services commonly include, but are not limited to:
  1. Getters and Setters that allow the reading and writing of the MBean's Attributes. For example, an MBean might represent a thread pool and an attribute named MaxPoolSize could be read to determine what the maximum allowable size of the pool is, while writing the attribute would modify the maximum allowable size of the pool that the MBean is managing.
  2. Operations that execute a specific piece of functionality in an MBean. Operations can be thought of as bean methods that do not fit the attribute (or Java Bean property) model. They may have no return value and have zero, one or more parameters. For example, an operation called stop might stop the thread pool that is managed by an MBean.
  3. MBeans may emit Notifications when a specific condition is met, or the MBean detects a specific event. Notifications can be subscribed to by NotificationListeners that have registered to be notified of these events. For example, an MBean might send notifications when the thread pool it manages is started, and then again when it is stopped.
• MBeanServer: The MBeanServer plays multiple roles in a JMX environment:
  • It is the central registry for MBeans within a given JMX domain. As the registry, the MBeanServer provides functionality to register, unregister, enumerate and search for MBeans.
  • The MBeanServer provides the invocation interface for accessing registered MBeans. When a thread wants to read or write attributes, execute an operation or [un]register a notification listener in an MBean instance, it does so through the MBeanServer by providing the ObjectName of the target MBean and the parameters of the invocation.
• ObjectName: This is a composite key that serves to both define the unique identity of one MBean, and as pattern that describes a group of MBeans that have matching sub-keys of their ObjectNames in common. There are 2 parts to an ObjectName:
  1. The Domain Name:
  2. The Key Properties: