// nothing
            if (logger.isInfoEnabled()) {
                logger.info("No crawling target urls.");
            }
            return;
        }

        doCrawl(sessionId, configList);
    }

    protected void doCrawl(final String sessionId, final List<DataConfig> configList) {
        final int multiprocessCrawlingCount = ComponentUtil.getFessConfig().getCrawlingThreadCount();

            if (logger.isInfoEnabled()) {
                logger.info("No crawling target urls.");
            }
            return;
        }

        doCrawl(sessionId, webConfigList, fileConfigList);
    }

    protected void doCrawl(final String sessionId, final List<WebConfig> webConfigList, final List<FileConfig> fileConfigList) {

        } catch (final Exception e) {
            logger.warn("Failed to store crawling information.", e);
        }

        try {
            return crawler.doCrawl(options);
        } finally {
            try {
                crawlingInfoHelper.store(options.sessionId, false);
            } catch (final Exception e) {

 *   private Queue<Uri> toCrawl;
 *   protected void startUp() throws Exception {
 *     toCrawl = readStartingUris();
 *   }
 *
 *   protected void runOneIteration() throws Exception {
 *     Uri uri = toCrawl.remove();
 *     Collection<Uri> newUris = crawl(uri);
 *     visited.add(uri);
 *     for (Uri newUri : newUris) {
 *       if (!visited.contains(newUri)) { toCrawl.add(newUri); }
 *     }
 *   }
 *