JMX 2.0 defines a new API for creating hierarchical namespaces in an MBeanServer. An ObjectName domain can now start with a path-like string (using // as separator) which identifies the namespace in which the named MBean is registered.

Some restrictions apply to the ObjectName pattern that can be passed to the MBeanServer when performing queries on MBean registered in namespaces:
It is only possible to query for MBeans using ObjectName patterns of the form:
   [<path-element without-pattern>//]*<pattern-without-path>

However, it is still possible to define ObjectName patterns of the form
   [<pattern | path-element>//]*<pattern-without-path>
and to apply those patterns to any objectname.

How ObjectName patterns are matched with regards to namespaces is currently underspecified - the javadoc of various JMX classes needs to be updated to clarify the behaviour of pattern matching and MBeanServer queries with regards to namespaces.