docs: public long videoPreview(String wxName, String openId, String mediaId, String title, String desc) {
  		Map<String, String> uploadRequest = new HashMap<>();
  		uploadRequest.put("media_id", mediaId);
  		uploadRequest.put("title", title);
  		uploadRequest.put("description", desc);
  		String uploadUrl = WxEndpoint.get("url.mass.message.video.upload");
  		String json = JsonMapper.nonEmptyMapper().toJson(uploadUrl);
  
  		String response = wxClient.post(uploadUrl, json);
  		Map<String, Object> result = JsonMapper.defaultMapper().json2Map(response);
  		if (result.containsKey("media_id")) {
  			return preview(wxName, openId, "mpvideo", (String) result.get("media_id"));
  		} else {
  			throw new WxRuntimeException(999, "send mp video preview failed.");
  		}
  	}