i have to Test some Messege Driven Beans. how can i test their performance in JMeter?
The only thing you can reliably test for MDBs with JMeter is performance of the client which uses them. JMeter is specifically for HTTP requests, so you can't directly test an MDB.
It also depends what you mean by "performance". If you mean the performance of an application server which uses MDBs, you could get a general feel by ramping up calls to code which uses the MDBs and profile the behaviour of the server. If you mean client response times using MDBs just use JMeter as normal (assuming your client is a Web App).