code: public Boolean notifyId(String notifyId){
          String url = Alipay.GATEWAY +
                  "&" + AlipayField.SERVICE.field() + "=" + Service.NOTIFY_VERIFY.value() +
                  "&" + AlipayField.PARTNER.field() + "=" + alipay.merchantId +
                  "&" + AlipayField.NOTIFY_ID.field() + "=" + notifyId;
          String resp = Http.get(url).request();
          return "true".equalsIgnoreCase(resp);
      }
docs: 验证支付通知ID是否合法
  @param notifyId 通知ID，后置通知中会有
  @return 合法返回true，反之false