}
        };
        CrawlingParameterUtil.setDataService(service);
        assertNotNull(CrawlingParameterUtil.getDataService());

        // Set to null
        CrawlingParameterUtil.setDataService(null);

        // Should be null now
        assertNull(CrawlingParameterUtil.getDataService());
    }

    public void test_threadLocal_isolation() throws Exception {
        // Set values in main thread

 * UrlQueueService<UrlQueue<?>> urlQueueService = CrawlingParameterUtil.getUrlQueueService();
 * CrawlingParameterUtil.setUrlQueueService(newUrlQueueService);
 *
 * DataService<AccessResult<?>> dataService = CrawlingParameterUtil.getDataService();
 * CrawlingParameterUtil.setDataService(newDataService);
 * }
 * </pre>
 *
 * <p>Note: If a parameter is set to {@code null}, the corresponding ThreadLocal variable is removed.</p>
 */

                    logger.debug("Storing accessResult: {}", accessResult);
                }
                try {
                    // store
                    CrawlingParameterUtil.getDataService().store(accessResult);
                } catch (final Exception e) {
                    crawlerContext.decrementAndGetAccessCount();
                    if (urlQueueService.visited(urlQueue)) {

        String enc = parentEncodingMap.get(key);
        if (enc != null) {
            return enc;
        }

        final AccessResult<?> accessResult = ComponentUtil.getDataService().getAccessResult(sessionId, parentUrl);
        if (accessResult != null) {
            final AccessResultData<?> accessResultData = accessResult.getAccessResultData();

        return getComponent(DICTIONARY_MANAGER);
    }

    /**
     * Gets the data service component.
     * @return The data service.
     */
    public static DataService<OpenSearchAccessResult> getDataService() {
        return getComponent(DATA_SERVICE);
    }

    /**
     * Gets the search engine client component.
     * @return The search engine client.
     */