code: @RequestMapping(method = RequestMethod.GET)
      @ResponseBody
      protected final String bind(HttpServletRequest request) {
          if (isLegal(request)) {
              //绑定微信服务器成功
              return request.getParameter("echostr");
          } else {
              //绑定微信服务器失败
              return "";
          }
      }
docs: 绑定微信服务器
  
  @param request 请求
  @return 响应内容