code: public static Cookie getCookie(HttpServletRequest request, String cookieName) {
          if (cookieName == null || request == null) {
              return null;
          }
          Cookie[] cks = request.getCookies();
          if (cks == null) {
              return null;
          }
          for (Cookie cookie : cks) {
              if (cookieName.equals(cookie.getName())) {
                  return cookie;
              }
          }
          return null;
      }
docs: 获取cookie
  
  @param request
  请求request
  @param cookieName
  cookie名
  @return cookie