i gues u are trying to just logout user... try that:
public String logout(){
javax.servlet.http.HttpServletRequest request =
(javax.servlet.http.HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest();
javax.servlet.http.HttpSession session = request.getSession();
session.invalidate();
session = request.getSession(true); return "after_logout";
}bu if u want to null only particular beans than u must find them in "session"
somme time ago Matthias Wessendorf show my the this way... thanks again Matthias
Slawek
How can you access the managed session beans map if you wanted to have them nullified for a particular user?

