code: private String getRedirectUrl(RequestParametersHolder requestHolder) throws AlipayApiException {
          StringBuffer urlSb = new StringBuffer(serverUrl);
          try {
              Map<String, String> sortedMap = AlipaySignature.getSortedMap(requestHolder);
              String sortedQuery = WebUtils.buildQuery(sortedMap, charset);
              urlSb.append("?");
              urlSb.append(sortedQuery);
          } catch (IOException e) {
              throw new AlipayApiException(e);
          }
  
          return urlSb.toString();
      }
docs: GET模式下获取跳转链接
  
  @param requestHolder
  @return
  @throws AlipayApiException