code: public static String getCookieValue(HttpServletRequest request, String cookieName) {
      try {
        Cookie cookie = getCookie(request, cookieName);
        if (null == cookie) {
          return null;
        } else {
          return URLDecoder.decode(cookie.getValue(), "utf-8");
        }
      } catch (Exception e) {
        return null;
      }
    }
docs: 获取cookie中的value<br>
  自动负责解码<br>
  
  @param request
  @param cookieName
  @return null when cannot find the cookie