I'm writing an application which requires quite a few long
lived services, which are singletons and have their own
dedicated thread of control. I'd like the ability to
maintain state as well.

It seems that MBeans are the only way to do this within
the J2EE framework. Can sometime tell me whether this is
correct?

If not, how should it be done?

If so, then I'd like to understand how easy it is for
MBeans to communicate with each other and whether there are any reasons not to do so.

There will be a number of SLSBs needing to communicate
with the MBeans as well.

Any help greatly appreciated.