final Locale locale = ComponentUtil.getRequestManager().getUserLocale();
        if (locale != null) {
            final String lang = locale.getLanguage();
            if (ComponentUtil.getFessConfig().isOnlineHelpSupportedLang(lang)) {
                target = lang.toUpperCase(Locale.ROOT);
            }
        }
        return url.replaceFirst("\\{lang\\}", target == null ? "EN" : target);
    }

    /**

        return split(getSupportedLanguages(), ",").get(stream -> stream.filter(StringUtil::isNotBlank).toArray(n -> new String[n]));
    }

    String getOnlineHelpSupportedLangs();

    default boolean isOnlineHelpSupportedLang(final String lang) {
        if (StringUtil.isBlank(getOnlineHelpSupportedLangs())) {
            return false;
        }