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).
JMX uses a three-level architecture:
- The Probe level - also called the Instrumentation level - contains the probes (called MBeans) instrumenting the resources
- The Agent level, or MBeanServer - the core of JMX. It acts as an intermediary between the MBean and the applications.
- The Remote Management level enables remote applications to access the MBeanServer through connectors and adaptors. A connector provides full remote access to the MBeanServer API using various communication (RMI, IIOP, JMS, WS-* …), while an adaptor adapts the API to another protocol (SNMP, …) or to Web-based GUI (HTML/HTTP, WML/HTTP, …).
Managed Bean
A managed bean - sometimes simply referred to as an MBean - is a type of JavaBean, created with dependency injection. Managed Beans are particularly used in the Java Management Extensions technology. But with Java EE 6, the specification provides for a more detailed meaning of a managed bean.
The MBean represents a resource running in the Java virtual machine, such as an application or a Java EE technical service (transactional monitor, JDBC driver, etc.). They can be used for collecting statistics on concerns like performance, resources usage, or problems (pull); for getting and setting application configurations or properties (push/pull); and notifying events like faults or state changes (push).
Types
There are two basic types of MBean:
- Standard MBeans implement a business interface containing setters and getters for the attributes and the operations (i.e., methods).
- Dynamic MBeans implement the
javax.management.DynamicMBeaninterface that provides a way to list the attributes and operations, and to get and set the attribute values.
Additional types are Open MBeans, Model MBeans and Monitor MBeans. Open MBeans are dynamic MBeans that rely on the basic data types. They are self-explanatory and more user-friendly. Model MBeans are dynamic MBeans that can be configured during runtime. A generic MBean class is also provided for dynamically configuring the resources during program runtime.
An MXBean (Platform MBean) is a special type of MBean that reifies Java Virtual Machine subsystems such as garbage collection, JIT compilation, memory pools, multi-threading, etc.