ResponseData responseData = new ResponseData();
        Map<String, Object> dataMap = new HashMap<>();
        assertEquals("", documentHelper.getContent(null, responseData, null, dataMap));
        assertEquals("", documentHelper.getContent(null, responseData, "", dataMap));
        assertEquals("", documentHelper.getContent(null, responseData, " ", dataMap));

     * Get the extractor.
     * @param responseData The response data.
     * @return The extractor.
     */
    protected abstract Extractor getExtractor(ResponseData responseData);

    @Override
    public ResultData transform(final ResponseData responseData) {
        if (responseData == null || !responseData.hasResponseBody()) {
            final String url = responseData != null ? responseData.getUrl() : "unknown";

                if (responseData == null) {
                    // head method
                    responseData = client.execute(RequestDataBuilder.newRequestData().head().url(url).build());
                    if (responseData == null) {
                        return true;
                    }
                }

                final int httpStatusCode = responseData.getHttpStatusCode();

        try (final ResponseData responseData = client.execute(RequestDataBuilder.newRequestData().get().url(url).build())) {
            if (responseData.getRedirectLocation() != null) {
                final Set<RequestData> childUrlList = new HashSet<>();
                childUrlList.add(RequestDataBuilder.newRequestData().get().url(responseData.getRedirectLocation()).build());

     */
    public List<String> getFileRoleTypeList(final ResponseData responseData) {
        final List<String> roleTypeList = new ArrayList<>();
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        if (fessConfig.isFileRoleFromFile() && responseData.getUrl().startsWith("file:")) {
            final Map<String, Object> metaDataMap = responseData.getMetaDataMap();

     * for thumbnail generation.
     *
     * @param responseData the response data containing MIME type information
     * @return true if the MIME type represents a supported image format, false otherwise
     */
    protected boolean isImageMimeType(final ResponseData responseData) {
        final String mimeType = responseData.getMimeType();
        if (mimeType == null) {
            return true;
        }

                try (final ResponseData responseData = client.execute(RequestDataBuilder.newRequestData().get().url(u).build())) {
                    if (StringUtil.isNotBlank(responseData.getRedirectLocation())) {
                        u = responseData.getRedirectLocation();
                        continue;
                    }
                    if (StringUtil.isBlank(responseData.getUrl())) {

        try (final ResponseData responseData = client.execute(RequestDataBuilder.newRequestData().get().url(url).build())) {
            if (responseData.getRedirectLocation() != null) {
                return responseData.getRedirectLocation();
            }
            responseData.setExecutionTime(systemHelper.getCurrentTimeAsLong() - startTime);

            final org.codelibs.fess.crawler.entity.ResultData resultData = new org.codelibs.fess.crawler.entity.ResultData();
            Map<String, Object> dataMap = new HashMap<>();
            if (responseData != null) {
                dataMap.put("url", responseData.getUrl());
            }

        }

        return process(thumbnailId, responseData -> {
            final String mimeType = responseData.getMimeType();
            final String extension = getExtensionFromMimeType(mimeType);
            final File tempFile = ComponentUtil.getSystemHelper().createTempFile("thumbnail_", extension);
            try {
                CopyUtil.copy(responseData.getResponseBody(), tempFile);