public void logout(HttpServletRequest request, HttpServletResponse response) throws IOException {
Cookie cookie = HttpUtil.getCookie("userid", request);
if (cookie == null) cookie = new Cookie("userid", "");
cookie.setMaxAge(0);
response.addCookie(cookie);
cookie = HttpUtil.getCookie("username", request);
if (cookie == null) cookie = new Cookie("username", "");
cookie.setMaxAge(0);
response.addCookie(cookie);
}
