how to get current user of portal in jsp (1 only login)

Hi,

i have do it how Jorge sais here how-to-get-current-user-of-portal-in-jspservlet , and run ok, but my problem is that now i have 2 logins:

1) Login in the Portal

2) Login in jsp

How can i do to have only 1 login (portal login) and obtain portal user?

Thank you