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

        return normalizeLang(value);
    }

    /**
     * Normalizes a language string.

     * The value is, e.g.  <br>
     * comment: Default language for HTML documents.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getCrawlerDocumentHtmlDefaultLang();

    /**
     * Get the value for the key 'crawler.document.html.default.lang' as {@link Integer}. <br>
     * The value is, e.g.  <br>
     * comment: Default language for HTML documents.