I agree with you Karthik.
If we do understand the fundamentals, design and architecture of any technology then you can easily fit into new technology even you do not know the new technology.
For example if you know fundamentals of RMI and its architecture it is easy to pick either CORBA,
EJB or Web Services(even though web services do things differently). After all most of the new technologies revolving around Object and how we can pass this object here and there
Coming to technologies like Xdoclet you mentioned, those kind of technologies we learn when we start exploring how to make best design or architecture and write efficient code.