Java API to create/generate a SSO login ticket

We are writing J2EE application which suppose to run on almost any Application Server.

The application has to connect to R/3 system using JCo and login ticket (because only user name is known).

We are looking for a security Java API which will generate a SSO login ticket which can be passed to JCo.

Is there any? What are requirements (public/private parts, etc..)?

Any examples?

Thanks in advance,

Igor