how can I read the used authentication scheme in a server?

[Stephan Koops]

Hi Bruno and all,

JAX-RS has a method in the API, where the application developer could 
request, which authenticaton scheme was used 
(SecurityContext.getAuthenticationScheme(), if someone is interested)
If the request was authenticated by BASIC, DIGEST, client certificate or 
Servlet form authentication, I have to return a given constant for them.
Check for BASIC and DIGEST is easy, but how can I check, if the request 
was authenticated by SSL client certificate? And how can I check, if it 
was Servlet form authentication?

best regards
   Stephan