public String cerrarSesion() {
   HttpSession session =
       (HttpSession) FacesContext.getCurrentInstance().getExternalContext().getSession(false);
   session.invalidate();
   WebUtil.sendRedirect("/login/login.jsf");
   return "RELOGEA";
 }
 public String irPrincipal() {
   WebUtil.sendRedirect("/paginas/inicio.jsf");
   return "";
 }