* <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> CRAWLER_CONTEXT_THREAD_LOCAL = new ThreadLocal<>();

    return requireNonNull(DEST_TL.get());
  }

  /**
   * A thread-local destination buffer to keep us from creating new buffers. The starting size is
   * 1024 characters. If we grow past this we don't put it back in the threadlocal, we just keep
   * going and grow as needed.
   */
  private static final ThreadLocal<char[]> DEST_TL =
      new ThreadLocal<char[]>() {

    /** Constant for Kryo serializer type. */
    protected static final String KRYO = "kryo";

    /** ThreadLocal container for Kryo instances to ensure thread safety. */
    protected final ThreadLocal<Kryo> kryoThreadLocal;

    /**
     * Constructs a new DataSerializer.
     * <p>
     * Initializes the ThreadLocal Kryo instances with appropriate configuration.

   *
   * <p>This class would certainly be simpler and easier to reason about if it were built with
   * ThreadLocal; however, ThreadLocal is not well optimized for the case where the ThreadLocal is
   * non-static, and is initialized/removed frequently - this causes churn in the Thread specific
   * hashmaps. Using a static ThreadLocal to avoid that overhead would mean that different

   *
   * <p>This class would certainly be simpler and easier to reason about if it were built with
   * ThreadLocal; however, ThreadLocal is not well optimized for the case where the ThreadLocal is
   * non-static, and is initialized/removed frequently - this causes churn in the Thread specific
   * hashmaps. Using a static ThreadLocal to avoid that overhead would mean that different

        public void run() {}
      };

  public void testDirectExecutorServiceServiceInThreadExecution() throws Exception {
    ListeningExecutorService executor = newDirectExecutorService();
    ThreadLocal<Integer> threadLocalCount =
        new ThreadLocal<Integer>() {
          @Override
          protected Integer initialValue() {
            return 0;
          }
        };
    Runnable incrementTask =
        new Runnable() {

        public void run() {}
      };

  public void testDirectExecutorServiceServiceInThreadExecution() throws Exception {
    ListeningExecutorService executor = newDirectExecutorService();
    ThreadLocal<Integer> threadLocalCount =
        new ThreadLocal<Integer>() {
          @Override
          protected Integer initialValue() {
            return 0;
          }
        };
    Runnable incrementTask =
        new Runnable() {

   */
  // This is logically a Set, but an ArrayList is used to minimize the amount
  // of allocation done on lock()/unlock().
  private static final ThreadLocal<List<LockGraphNode>> acquiredLocks =
      new ThreadLocal<List<LockGraphNode>>() {
        @Override
        protected List<LockGraphNode> initialValue() {
          return newArrayListWithCapacity(3);
        }
      };

  /**

 *
 * @author shinsuke
 */
public class CrawlingParameterUtilTest extends PlainTestCase {

    @Override
    protected void tearDown() throws Exception {
        // Clean up ThreadLocal variables after each test
        CrawlingParameterUtil.setUrlQueue(null);
        CrawlingParameterUtil.setCrawlerContext(null);
        CrawlingParameterUtil.setUrlQueueService(null);

    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