public void doGet(HttpServletRequest req, HttpServletResponse res)
      throws ServletException, IOException {

    res.setContentType("text/html");
    PrintWriter out = res.getWriter();
    Enumeration values = req.getParameterNames();
    String name = "";
    String value = "";
    String id = "";
    while (values.hasMoreElements()) {
      name = ((String) values.nextElement()).trim();
      value = req.getParameter(name).trim();
      if (name.equals("id")) id = value;
    }
    if (url.equals("")) {
      url = getServletContext().getInitParameter("url");
      cas_url = getServletContext().getInitParameter("cas_url");
    }
    HttpSession session = null;
    session = req.getSession(false);
    if (session != null) {
      session.invalidate();
    }
    res.sendRedirect(cas_url);
    return;
  }