code: public CdnResult.BandwidthResult getBandwidthData(String[] domains, String startDate, String endDate,
                                                        String granularity) throws QiniuException {
          HashMap<String, String> req = new HashMap<>();
          req.put("domains", StringUtils.join(domains, ";"));
          req.put("startDate", startDate);
          req.put("endDate", endDate);
          req.put("granularity", granularity);
  
          byte[] body = Json.encode(req).getBytes(Constants.UTF_8);
          String url = server + "/v2/tune/bandwidth";
          StringMap headers = auth.authorizationV2(url, "POST", body, Client.JsonMime);
          Response response = client.post(url, body, headers, Client.JsonMime);
          return response.jsonToObject(CdnResult.BandwidthResult.class);
      }
docs: 获取域名访问带宽数据
  参考文档：<a href="http://developer.qiniu.com/fusion/api/traffic-bandwidth">流量带宽</a>
  
  @param domains     待获取数据的域名列表
  @param startDate   开始日期，格式为：2017-02-18
  @param endDate     截至日期，格式为：2017-02-20
  @param granularity 数据粒度，支持的取值为 5min ／ hour ／day
  @return 获取带宽数据请求的回复