How to handle validations in WebServices

[vikram karne]

Hi Friends

I wanted to discuss regarding how the validations are done in webservices.
I am exposing methods present in the session beans as a webservice.
I have written a Handler/Delegate class where i do the necessary conversions for the method return types and parameters.

we�re now bypassing the input validation that may or may not exist in the UI layer, by going directly against the entities.So i wanted to know where these validations need to be done now as it is very critical senario.
should this be handled in the Session Bean methods, Delegate layer or in the WSDL itself.

Please let me know about the procedure of how this is done in case any one of you have already implemented the same.
waiting for a positive reply from your side.

Regards
Vikram K