code: public UploadMediaResponse uploadNews(List<Article> articles){
          UploadMediaResponse response;
          String url = BASE_API_URL + "cgi-bin/media/uploadnews?access_token=#";
          final Map<String, Object> params = new HashMap<String, Object>();
          params.put("articles", articles);
          BaseResponse r = executePost(url, JSONUtil.toJson(params));
          response = JSONUtil.toBean(r.getErrmsg(), UploadMediaResponse.class);
          return response;
      }
docs: 上传群发文章素材。
  
  @param articles 上传的文章信息
  @return 响应对象