*
     * @param doc The document to update.
     */
    public void updateDocument(final Map<String, Object> doc) {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        String language = getSupportedLanguage(DocumentUtil.getValue(doc, fessConfig.getIndexFieldLang(), String.class));
        if (language == null) {
            for (final String f : langFields) {
                if (doc.containsKey(f)) {