Hi Aditi.
I'm not a Weblogic guy, but I was looking over the 8.1 docs and it seems it implements J2EE 1.3 and JAX-RPC 1.0. Being that the case, the method of deployment of Message Handlers is not mandated by the spec. See JAX-RPC 1.0 12.3.2. That changes for J2EE 1.4 when webservices.xml is used.
There seems to be some good docs for Weblogic though. Take a ook at this one, which guides you specifically on designing, building and deploying Message Handlers with Weblogic 8.1:
"Creating SOAP Message Handlers to Intercept the SOAP Message" And
this one is the parent doc. Lots of info.
Hope it helps and don't forget to share the results of your implementation.
Regards.