final String xpath = xpathConfigMap.get(XPath.DEFAULT_LANG);
        if (StringUtil.isNotBlank(xpath)) {
            return xpath;
        }
        return fessConfig.getCrawlerDocumentHtmlLangXpath();
    }

    protected String getContentXpath(final FessConfig fessConfig, final Map<String, String> xpathConfigMap) {
        final String xpath = xpathConfigMap.get(XPath.DEFAULT_CONTENT);

     * The value is, e.g. //HTML/@lang <br>
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getCrawlerDocumentHtmlLangXpath();

    /**
     * Get the value for the key 'crawler.document.html.digest.xpath'. <br>
     * The value is, e.g. //META[@name='description']/@content <br>