}

    /**
     * Normalizes an HTML language string.
     *
     * @param value The language string to normalize.
     * @return The normalized language string.
     */
    public String normalizeHtmlLang(final String value) {
        final String defaultLang = ComponentUtil.getFessConfig().getCrawlerDocumentHtmlDefaultLang();
        if (StringUtil.isNotBlank(defaultLang)) {
            return defaultLang;
        }

        if (documentExpires != null) {
            putResultDataBody(dataMap, fessConfig.getIndexFieldExpires(), documentExpires);
        }
        // lang
        final String lang = systemHelper.normalizeHtmlLang(
                getSingleNodeValue(document, getLangXpath(fessConfig, xpathConfigMap), node -> pruneNode(node, crawlingConfig)));
        if (lang != null) {