*
     * @param key   the key of the feature
     * @param value the value of the feature
     */
    public void addFeature(final String key, final String value) {
        if (StringUtil.isBlank(key) || StringUtil.isBlank(value)) {
            throw new CrawlerSystemException("key or value is null.");
        }

        featureMap.put(key, value);
    }

    /**
     * Adds a property to the extractor.

                    } finally {
                        CloseableUtil.closeQuietly(in);
                    }
                }, contentEncoding, normalizeText);
                if (StringUtil.isBlank(content)) {
                    if (resourceName != null) {
                        if (logger.isDebugEnabled()) {
                            logger.debug("retry without a resource name: {}", resourceName);

     * @param enc the character encoding to use
     * @return the encoded URL
     */
    protected String encodeUrl(final String url, final String enc) {
        if (StringUtil.isBlank(url) || StringUtil.isBlank(enc)) {
            return url;
        }

        final StringBuilder buf = new StringBuilder(url.length() + 100);
        for (final char c : url.toCharArray()) {

        final String endpoint = getInitParameter("endpoint", null, String.class);
        if (StringUtil.isBlank(endpoint)) {
            throw new CrawlingAccessException("endpoint is blank.");
        }
        builder.endpoint(endpoint);
        final String accessKey = getInitParameter("accessKey", null, String.class);
        if (StringUtil.isBlank(accessKey)) {
            throw new CrawlingAccessException("accessKey is blank.");
        }

                for (int i = 0; i < tokens.size(); i++) {
                    final AnalyzeToken token = tokens.get(i);
                    final String word = token.getTerm();
                    if (StringUtil.isBlank(word)) {
                        continue;
                    }
                    final String[] words = { word };
                    final String[][] readings = new String[words.length][];

            final String secretKey = System.getenv().get("STORAGE_SECRET_KEY");
            final String region = System.getenv().get("STORAGE_SECRET_KEY");
            try {
                if (StringUtil.isBlank(endpoint)) {
                    throw new IOException("endpoint is blank.");
                }
                final Builder builder = MinioClient.builder().endpoint(endpoint);

            dfos = out;
            CopyUtil.copy(in, out);
            out.flush();

            Extractor extractor = StringUtil.isBlank(mimeType) ? null : extractorFactory.getExtractor(mimeType);
            if (extractor == null) {
                final String detectedMimeType = getMimeType(out);

            return name.substring(pos + 1);
        }
        return name;
    }

    private void executeCommand(final File inputFile, final File outputFile) {

        if (StringUtil.isBlank(command)) {
            throw new CrawlerSystemException("command is empty.");
        }

        final Map<String, String> params = new HashMap<>();
        params.put("$INPUT_FILE", inputFile.getAbsolutePath());

     * @return true if the URL has been visited, false otherwise.
     */
    @Override
    public boolean visited(final OpenSearchUrlQueue urlQueue) {
        final String url = urlQueue.getUrl();
        if (StringUtil.isBlank(url)) {
            if (logger.isDebugEnabled()) {
                logger.debug("URL is a blank: {}", url);
            }
            return false;
        }

        final String loginUrl = replaceCredentials(credentials, originalLoginUrl);
        final String loginReqParams = replaceCredentials(credentials, getParameter(LOGIN_PARAMETERS));

        if (StringUtil.isBlank(loginUrl)) {
            if (logger.isDebugEnabled()) {
                logger.debug("No login.url");
            }
            return;
        }

        final HttpUriRequest httpRequest;