*
     * @param config the crawling configuration containing time-to-live settings
     * @return the document expiration date, or null if no expiration is set
     */
    public Date getDocumentExpires(final CrawlingConfig config) {
        if (config != null) {
            final Integer timeToLive = config.getTimeToLive();
            if (timeToLive != null) {
                // timeToLive minutes

                    storeChildUrlsToQueue(urlQueue, getAnchorSet(document.get(fessConfig.getIndexFieldAnchor())));

                    final Date documentExpires = crawlingInfoHelper.getDocumentExpires(crawlingConfig);
                    if (documentExpires != null
                            && !indexingHelper.updateDocument(searchEngineClient, id, fessConfig.getIndexFieldExpires(), documentExpires)) {

        final PathMappingHelper pathMappingHelper = ComponentUtil.getPathMappingHelper();
        final Date documentExpires = crawlingInfoHelper.getDocumentExpires(crawlingConfig);
        final SystemHelper systemHelper = ComponentUtil.getSystemHelper();
        final FileTypeHelper fileTypeHelper = ComponentUtil.getFileTypeHelper();