return null;
        } catch (final ChildUrlsException | DataStoreCrawlingException e) {
            throw e;
        } catch (final Exception e) {
            final FessConfig fessConfig = ComponentUtil.getFessConfig();
            final Object configId = dataMap.get(fessConfig.getIndexFieldConfigId());
            throw new DataStoreCrawlingException(url, "Failed to add document. url: " + url + ", configId: " + configId, e);