docs: public Boolean refund(RefundDetail refundDetail){
          try {
              String url = Alipay.GATEWAY + "_input_charset=" + alipay.inputCharset;
              Map<String, String> refundParams = buildRefundParams(refundDetail);
              String resp = Http.get(url).params(refundParams).request();
              XmlReaders reader = XmlReaders.create(resp);
              String isSuccess = reader.getNodeStr("is_success");
              if ("T".equals(isSuccess)){
                  return Boolean.TRUE;
              }
          } catch (XmlException e){
              // ignore xml parse error
          } catch (Exception e){
              throw new AliPayException(e);
          }
          return Boolean.FALSE;
      }