User Name in JSR168 Portlet

[Praveen Dharmavaram]

I have a JSR168 Portlet which runs on WebSphere Portal Server(5.1). I want to get hold of the user name from the WPS. I have tried to get the username unsuccessfully by doing "RenderRequest.getUserPrincipal().getName()", but the value comes out to be "null". Any Ideas on how to get the username.

Thanks
Praveen