“Hello World,” the JMX way - JMX in Action - page 29

2.3 Creating a JMX agent

Now that you have your first MBean, you need to make it available for use. To do
so, you must register it in a JMX agent. Therefore, you need to create the Hello-
Agent class, which is a simple JMX agent.
As described in chapter 1, JMX agents are JMX components in the agent layer
of JMX and are the containers for MBeans. Part 3 of the topic covers JMX agents
in detail.
The HelloAgent class performs three important tasks:
■ It creates an MBeanServer instance to contain MBeans.
■ It creates an HTML adapter to handle connections from HTML clients.
■ It registers a new instance of the HelloWorld MBean.

As you are about to see, the HelloAgent class is probably the simplest agent you will
ever write, but it is still quite powerful. This fact again highlights one of the bene-
fits of using JMX : it is simple and yet useful. In a matter of moments, you have
developed the HelloWorld MBean. You can now easily manage this MBean by writ-
ing a simple agent that uses the HTML adapter provided by Sun Microsystems.
Using any web browser, the adapter allows you to interact with the agent to view
all registered MBeans and their attributes. Figure 2.3 depicts this interaction.
Specifically, the adapter lets you:
■ View the readable MBean attributes
■ Update the writable attributes
■ Invoke the other remaining methods

Figure 2.3 Using a Web browser to contact the HTML adapter present in the MBean server