CAS with JSF

[Paulo Cheque]

Hi, I am using CAS with JSF (MyFaces) but I am having problems getting
the username that has logged in.

MyCode:

FacesContext facesContext = FacesContext.getCurrentInstance();
HttpSession session = (HttpSession)
facesContext.getExternalContext().getSession(false);
session.getAttribute("edu.yale.its.tp.cas.cient.filter.user");

Last command always returns null.

Anyone know what I am doing wrong or any link where I can get help?

Thanks in advance
Paulo