Java Reference
In-Depth Information
If you have some knowledge of
JMX
or have read the
JMX
specification, you might
have wondered where the Open MBean was among the chapters covering the
other MBean types. At the time we're writing this topic, the Open MBean is an
optional, and not completely defined, part of the
JMX
specification. Without com-
plete knowledge of the Open MBean, we couldn't devote a complete chapter to it.
However, we can write a pretty fair appendix about what is covered in the
JMX
specification describing the Open MBean. This appendix contains the
material found in the spec, but does not include any working examples. Be
aware that the information presented in this appendix may change, and perhaps
has already.
A.1 What is an Open MBean?
Open MBeans are designed to be the most flexible and most richly self-descriptive
MBeans. They are built around a small set of basic data types that are used for all
parameters, return types, and attributes. Open MBeans are intended to provide
very meaningful descriptions of all their attributes and operations. These
descriptions should be of such detail that they might include possible values for
MBean attributes.
An Open MBean implements the
DynamicMBean
interface. What sets Open
MBeans apart from Dynamic MBeans is the quality of their metadata. The Open
MBean metadata is a rich description of its predefined data types. All Open
MBeans behave identically to Dynamic MBeans, except for their sole use of the
Open MBean basic data types (described shortly). It is the developer's responsi-
bility to ensure that the Open MBean uses only the set of basic data types for
every operation parameter, return type, and attribute of the MBean. Finally, an
Open MBean is identifiable by its use of the
OpenMBeanInfo
object as a return
type from the
getMBeanInfo()
method of the
DynamicMBean
interface.
Open MBeans would be useful in a management environment because users
would know ahead of time all the possible object types needed to interact with
the MBean. With Open MBeans, there would be no need for recompiling or
additional class loading.
A.2 Basic data types
The following list shows the set of objects that makes up the basic data types for
the Open MBean. The basic data type set includes the Java wrapper classes for
primitive types, plus some additional object types:
