* <p>Note: If a parameter is set to {@code null}, the corresponding ThreadLocal variable is removed.</p>
 */
public final class CrawlingParameterUtil {
    private static final ThreadLocal<UrlQueue<?>> URL_QUEUE_THREAD_LOCAL = new ThreadLocal<>();

    private static final ThreadLocal<CrawlerContext> ROBOT_CONTEXT_THREAD_LOCAL = new ThreadLocal<>();

    protected Map<String, String> metadataXpathMap = new HashMap<>();

    /** Thread-local instance of XPathAPI for thread-safe XPath evaluation. */
    private final ThreadLocal<XPathAPI> xpathAPI = new ThreadLocal<>();

    /**
     * Creates a new HtmlExtractor instance.
     */
    public HtmlExtractor() {
        super();
    }

    @Override

     */
    protected Set<String> robotsTxtUrlSet = new LruHashSet<>(10000);

    /**
     * Thread-local storage for sitemaps.
     */
    protected ThreadLocal<String[]> sitemapsLocal = new ThreadLocal<>();

    /** The number of threads used by the crawler */
    protected int numOfThread = 10;

    /** The maximum number of times to check for active threads. */

            + "^\\s*ios-app:|" //
            + "^\\s*callto:", Pattern.CASE_INSENSITIVE);

    /** Thread-local XPathAPI instance for thread-safe XPath operations. */
    private final ThreadLocal<XPathAPI> xpathAPI = new ThreadLocal<>();

    @Override
    public ResultData transform(final ResponseData responseData) {
        if (responseData == null || !responseData.hasResponseBody()) {