docs: public GetItemResponse getItem(GetItemRequest request)
              throws BceClientException, BceServiceException {
          checkNotNull(request, "request should not be null.");
          HttpMethodName method = HttpMethodName.GET;
          InternalRequest httpRequest = createRequestUnderInstance(method, 
                                                      MolaDbConstants.URI_TABLE, 
                                                      request.getTableName(),
                                                      MolaDbConstants.URI_ITEM);
          buildGetItemRequest(httpRequest, request);
          GetItemResponse ret = this.invokeHttpClient(httpRequest, GetItemResponse.class);
          return ret;
      }