docs: public CdnResult.RefreshResult refreshUrlsAndDirs(String[] urls, String[] dirs) throws QiniuException {
          //check params
          if (urls != null && urls.length > MAX_API_REFRESH_URL_COUNT) {
              throw new QiniuException(new Exception("url count exceeds the max refresh limit per request"));
          }
          if (dirs != null && dirs.length > MAX_API_REFRESH_DIR_COUNT) {
              throw new QiniuException(new Exception("dir count exceeds the max refresh limit per request"));
          }
  
          HashMap<String, String[]> req = new HashMap<>();
          if (urls != null) {
              req.put("urls", urls);
          }
          if (dirs != null) {
              req.put("dirs", dirs);
          }
          byte[] body = Json.encode(req).getBytes(Constants.UTF_8);
          String url = server + "/v2/tune/refresh";
          StringMap headers = auth.authorizationV2(url, "POST", body, Client.JsonMime);
          Response response = client.post(url, body, headers, Client.JsonMime);
          return response.jsonToObject(CdnResult.RefreshResult.class);
      }