A response to EasyMX - An alternative to JMX | Javalobby:
An advantages to using JMX is that the JMX client gets to the service via a different network path than the service's users. When the service is running well the path taken does not matter much. It is often the case, however, that the main service path becomes inaccessible under adverse conditions. Your HTTP requests are not being serviced before timeouts kick in, for example. And, consequently, your monitoring is also inaccessible. JMX clients use RMI or direct socket pathways to connect to the service and so the JMX client can continue to monitor and manage the service.
As Mr Fisher says (first comment to the posting), JMX is one of the "golden parts" of the Java ecosystem. (JBose was built on top of it.) Current JMX coding practices are more sophisticated than in the early days. The "MBean" and "MXBean" interface suffix continue to support quick and dirty monitoring and publishing. And for those with lots of monitoring and management touchpoints we too use sophisticated Java annotations processing to turn existing code into touchpoints.