Java Reference
In-Depth Information
Figure 1.4 Up-close view of an MBean server with registered MBeans and
agent services
exposed operation that configures the logging level of the application. At this
point, the MBean takes over, and we move into the instrumentation layer.
1.3.4
The instrumentation layer
The instrumentation layer is the closest layer to the managed resources. It com-
prises the MBeans registered in an agent. The MBean allows the resource to be
managed through the use of the
JMX
agent. Each MBean exposes a piece of the
configuration or functionality of an underlying resource; the MBean exposes
the management capabilities of the resource in a Java object. If the resource
does not natively speak Java, the MBean acts as a translator from the agent to
the resource.
For example, if you have a legacy application that exposes a management
capability through a lookup of data in a database table, you can build an MBean
that makes a JDBC call to the database tables to read or change data. The man-
agement application will not have to worry how the underlying technology is
built because the MBean abstracts it away.
An MBean is a lightweight class that knows how to use, acquire, and manipu-
late its resource in order to provide access or functionality to the agent and user.
Figure 1.5 shows an MBean directly interfacing with its resource.
