It is possible to monitor the various attributes exposed by JDK 1.5 through JMX. You can verify the following in your scenario :
1. The JNDI name in the "New Monitor" form for "JMX[MX4J/JDK1.5]" should be changed to "/jmxrmi" as this is the JNDI name and the port is as specified.
2. In case you are connecting from a remote machine i.e., the Applications Manager is running in a different machine from which your application(java program) is running then you need to specify the following system properties, before starting your application.
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=port number
You can then create the monitor. After creating the Monitor, you can use the "Add Attributes" link in the monitor details page (Custom Attributes) to add and monitor the various attributes exposed by the JVM.