*/
public abstract class Request<T extends Response> {
    /**
     * Constructs a new request.
     */
    public Request() {
        // nothing
    }

    /**
     * Executes the request.
     * @param client The OpenSearch client.
     * @return A Promise that will be resolved with the response or rejected with an error.
     */
    public Deferred<T>.Promise execute(final Client client) {

        assertNull(request.body());
    }

    @Test
    public void testConstructorWithNullUrl() {
        // URL can be null with the two-argument constructor
        CurlRequest request = new CurlRequest(Method.DELETE, null);

        assertEquals(Method.DELETE, request.method());
        assertEquals("UTF-8", request.encoding());
        assertEquals(1024 * 1024, request.threshold());

        // ## Act ##
        final CurlRequest request1 = Curl.get("http://example.com");
        final CurlRequest request2 = Curl.get("http://example.com");

        // ## Assert ##
        assertNotNull(request1);
        assertNotNull(request2);
        assertTrue("Factory methods should return different instances", request1 != request2);
    }

    @Test

    /**
     * Executes an index request.
     *
     * @param request The index request.
     * @return Future for the index response.
     */
    @Override
    public ActionFuture<IndexResponse> index(final IndexRequest request) {
        return client.index(request);
    }

    /**
     * Executes an index request asynchronously.
     *
     * @param request The index request.

     *
     * @param request the multi-search request
     * @return a future for the multi-search response
     */
    @Override
    public ActionFuture<MultiSearchResponse> multiSearch(final MultiSearchRequest request) {
        return client.multiSearch(request);
    }

    /**
     * Executes a multi-search request asynchronously with a callback.
     *

        PopularWordsRequest request = new PopularWordsRequest();
        request.setIndex("test-index");
        request.addTag("tag1");
        request.addRole("role1");
        request.addField("field1");
        request.addLanguage("ja");
        request.addExcludeWord("exclude");
        request.setQueryFreqThreshold(5);

        assertNotNull(request.buildQuery());
    }

    @Test

    /**
     * HTTP OPTIONS method constant used for CORS preflight requests.
     */
    protected static final String OPTIONS = "OPTIONS";

    @Override
    public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
            throws IOException, ServletException {
        final HttpServletRequest httpRequest = (HttpServletRequest) request;
        final String origin = httpRequest.getHeader("Origin");

     * @return a new CurlRequest object configured with the PUT method and the specified URL
     */
    public static CurlRequest put(final String url) {
        return new CurlRequest(Method.PUT, url);
    }

    /**
     * Creates a new CurlRequest with the DELETE method for the specified URL.
     *
     * @param url the URL to which the DELETE request will be sent

         * @return A new RequestParameter object with parsed values
         */
        protected static RequestParameter parse(final HttpServletRequest request) {
            final String query = request.getParameter("q");
            final String[] tags = getParamValueArray(request, "label");
            final String[] fields = getParamValueArray(request, "field");

    }

    /**
     * Configures the request with authentication and SSL settings.
     * @param request the request to configure
     * @return the configured request
     */
    protected CurlRequest request(final CurlRequest request) {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        final String username = fessConfig.getFesenUsername();