Called when a proposed update includes an update to the source bean.
The implementation should examine the proposed update and either
accept it (by returning) or reject it (by throwing a
BeanUpdateRejectedException). If the listener rejects the update,
the entire descriptor update will be aborted.
Called when a descriptor update has been abandoned that included an
proposed update to the source bean. Note that this method may not fail.
If a failure occurs during rollback, its effect should be logged and
isolated by the listener.