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JMX Tutorial Trail at java.sun.com -- JMX 1.4 specification -- JMX Documentation home

Concepts:

• An MBean is a resource (an object exposing methods).
• A JMX Agent exposes the MBean to the outside world. MBeans must be registered with an agent to be usable. (JMX agent extends MBean Server.) MBeans are registered / bound to an ObjectName.
• A JMX Connector is a client/server pair that exposes an MBean in a remote JVM.

ObjectName: domain : key1 = value1 [ , keyn = valuen ]+

• domain - a useful convention is to begin the domain name with the reverse DNS name of the organization that specifies the MBeans, followed by a period and a string whose interpretation is determined by that organization.
• See javadoc for escaping rules, patten matching, etc.

MBean interfaces:

• attributes are implicitly defined by the existence of getters and setters.
• a getter is any public method that does not return void and whose name begins with get. (is is also supported for methods returning boolean.)
• a setter is any public method that takes a single parameter and whose name begins with set.
• any other method is an operation.

An MBean must be of a public concrete class with a public constructor if it is to be instantiated by a JMX agent on demand from a management application.

Types of MBeans:

• Standard MBeans
  • a Java interface called SomethingMBean.
  • a Java class called Something that implements that interface.
  • the class and the interface names must match.
    • An object may be wrapped in a StandardMBean when the class and interface names do not match.
• MXBeans
  • a type of MBean that references only a predefined set of data types.
  • class name does not have to match the interface name.
  • a Java interface called SomethingMXBean
    -or- an interface annotated @MXBean
  • general principle is for simple types such as int or String to remain unchanged, while complex types such as MemoryUsage get mapped to the standard type CompositeDataSupport.
    • On a complex return value, the MXBean framework calls all the getters on the ReturnValue instance to convert the given instance into a CompositeData instance and uses the @ConstructorProperties annotation to reconstruct a ReturnValue instance from a CompositeData instance.
• Dynamic MBeans
  • must implement a specific interface, but they expose their management interface at runtime for greatest flexibility.
  • implement DynamicMBean - Attributes and operations are exposed through method calls on this interface.
• Open MBeans
  • are dynamic MBeans that rely on basic data types for universal manageability and that are self describing for user-friendliness.
• Model MBeans
  • are also dynamic MBeans that are fully configurable and self described at runtime; they provide a generic MBean class with default behavior for dynamic instrumentation of resources.
  • ((looks like an implementation of DynamicMBean that can be attached to an arbitrary class at runtime to expose it as an MBean))