> It would be very nice to know, how to use them and
> what functionality they provide.
they work similar to JBoss interceptors: you can control the mbean behaviour by intercepting the invocations going to the MBean and make decisions based on the data encapsulated in an invocation object.
the 1.0 codebase doesn't externalize the configuration yet so you will need to do a bit of coding if you want to add your custom ones. JBossMX 1.2 will have the interceptor stack configuration as part of the model mbean descriptors. things like security, attribute caching/mapping, life cycle services etc. can be implemented as interceptors and configured on an mbean basis.
For an example, see the classes in org.jboss.mx.interceptor package.