* <p>
     * Usage example:
     * </p>
     *
     * <pre>
     * StringUtil.defaultString(null, "NULL")  = "NULL"
     * StringUtil.defaultString("", "NULL")    = ""
     * StringUtil.defaultString("aaa", "NULL") = "aaa"
     * StringUtil.defaultString("aaa", null)   = "aaa"
     * StringUtil.defaultString(null, null)    = null
     * </pre>
     *
     * @param str

            if (StringUtil.isBlank(value)) {
                map = Collections.emptyMap();
            } else {
                final Set<String> keySet = new HashSet<>();
                map = split(value, "\n").get(stream -> stream.filter(StringUtil::isNotBlank).map(s -> {
                    final String[] pair = s.split("=");
                    if (pair.length == 1) {
                        return new Pair<>(StringUtil.EMPTY, pair[0].trim());

        final String slackWebhookUrls = fessConfig.getSlackWebhookUrls();
        if (StringUtil.isBlank(slackWebhookUrls)) {
            return;
        }
        final String body = toSlackMessage(discloser);
        StreamUtil.split(slackWebhookUrls, "[,\\s]").of(stream -> stream.filter(StringUtil::isNotBlank).forEach(url -> {

     * @return the host name, or empty string if URL is blank, or unknown hostname if parsing fails
     */
    default String getHost(final String u) {
        if (StringUtil.isBlank(u)) {
            return StringUtil.EMPTY; // empty
        }

        String url = u;
        final String originalUrl = url;

        int idx = url.indexOf("://");
        if (idx >= 0) {

        final String value = ComponentUtil.getFessConfig().getSystemProperty("oic.default.groups");
        if (StringUtil.isBlank(value)) {
            return StringUtil.EMPTY_STRINGS;
        }
        return split(value, ",").get(stream -> stream.filter(StringUtil::isNotBlank).map(String::trim).toArray(n -> new String[n]));
    }

    /**
     * Gets the default roles as an array.
     *

                return pagingQueryList.stream()
                        .filter(s -> prefix == null || !s.startsWith(prefix))
                        .collect(Collectors.joining("&", "&", StringUtil.EMPTY));
            }
            return null;
        }).orElse(StringUtil.EMPTY);
    }

    /**
     * Generates URL query parameters for facet filtering.
     *
     * @return URL-encoded query string containing facet parameters

     */
    public static String getAppType() {
        final String appType = System.getenv(FESS_APP_TYPE);
        if (StringUtil.isNotBlank(appType)) {
            return appType;
        }
        return StringUtil.EMPTY;
    }

    /**
     * Gets the override configuration path from environment variable when running in Docker.

                            .filter(StringUtil::isNotBlank)
                            .distinct()
                            .collect(Collectors.joining("\n")));
                    form.virtualHosts = stream(entity.getVirtualHosts())
                            .get(stream -> stream.filter(StringUtil::isNotBlank).map(String::trim).collect(Collectors.joining("\n")));

                        final String userCode = userInfoHelper.getUserCode();

                        if (StringUtil.isBlank(userCode)) {
                            throw new WebApiException(HttpServletResponse.SC_BAD_REQUEST, "No user session.");
                        }
                        if (StringUtil.isBlank(favoriteUrl)) {
                            throw new WebApiException(HttpServletResponse.SC_BAD_REQUEST, "URL is null.");

        // search
        if (StringUtil.isNotBlank(failureUrlPager.url)) {
            cb.query().setUrl_Wildcard(failureUrlPager.url);
        }

        if (StringUtil.isNotBlank(failureUrlPager.errorCountMax)) {
            cb.query().setErrorCount_LessEqual(Integer.parseInt(failureUrlPager.errorCountMax));
        }
        if (StringUtil.isNotBlank(failureUrlPager.errorCountMin)) {