Running the M-Let Agent Example

To run the m-let agent example for the JDK 1.1.x, you must have installed the Java Dynamic Management Kit for 1.1, and set your classpath accordingly. This example is located in the examplesDir/MLetAgent/ directory, see "Directories and Classpath" in the preface for details.

In our example, we have two MBeans representing geometrical shapes. Before running the example, we compile them and create a jar file for each. We also compile the agent application at the same time.

$ cd examplesDir/MLetAgent/
$ javac -classpath classpath *.java

$ jar cf Square.jar Square.class SquareMBean.class
$ rm Square.class SquareMBean.class

$ jar cf EquilateralTriangle.jar EquilateralTriangle.class \
EquilateralTriangleMBean.class
$ rm EquilateralTriangle.class EquilateralTriangleMBean.class

Since the MBean classes are only found in the jar files now, they cannot be found in our usual classpath, even if it includes the current directory (.). However, these jar files are given as the archive in the MLET tags of the HTML file, so the m-let loader should find them.

The agent requires you to specify the URL of the m-let file on command line. We have left this file in the examples directory, but you could place it and the jar files on a remote machine. With the Korn shell on the Solaris platform, you would type the following command:

$ java -classpath classpath Agent file:${PWD}/GeometricShapes.html

In the output of the agent, you can see it create the m-let service MBean, and then load the HTML file which specifies the three MBeans to be loaded. Once these have been loaded, we can see the two MBeans that were loaded directly through the class loader shortcut.

This agent uses the tracing mechanism, and you can select to receive the messages from the m-let loader by specifying the -DINFO_MLET property on the command line. The tracing mechanism is covered in the Java Dynamic Management Kit 4.2 Tools Reference guide and in the Javadoc API of the Trace class.

The agent then launches an HTML adaptor so that we can easily view the new MBeans. In them we can see that the values contained in the ARG tags of the m-let file were used to initialize the MBeans. Point your web browser to the following URL and click on the MBeans in the MLetExample domain:http://localhost:8082/. When you are done, type <Control-C> in the window where you launched the agent.