Java Development Tools

hi

i created a logout with JSF like SRDemoADFBC but when deploy in tomcat, i get the next error

java.lang.IllegalStateException: getAttribute: La Sesion ya ha sido invalidada

this is the code:

ExternalContext ectx = FacesContext.getCurrentInstance().getExternalContext();
HttpServletResponse response = (HttpServletResponse)ectx.getResponse();
HttpSession session = (HttpSession)ectx.getSession(false);
session.invalidate();
response.sendRedirect("Principal.jspx");