* @param target the target encoding name
     * @throws IllegalArgumentException if source or target is blank
     */
    public void addEncodingMapping(final String source, final String target) {
        if (StringUtil.isBlank(source) || StringUtil.isBlank(target)) {
            throw new IllegalArgumentException("Source and target encodings must not be blank.");
        }
        encodingMap.put(toLowerCase(source), target);
    }

    /**

     * @param maxLength The maximum content length in bytes
     * @throws CrawlerSystemException if the MIME type is blank or maxLength is negative
     */
    public void addMaxLength(final String mimeType, final long maxLength) {
        if (StringUtil.isBlank(mimeType)) {
            throw new CrawlerSystemException("MIME type is a blank.");
        }
        if (maxLength < 0) {

    }

    /**
     * Checks if the request header is valid.
     * A header is considered valid if its name is not blank and its value is not null.
     * @return true if the header is valid, false otherwise.
     */
    public boolean isValid() {
        if (StringUtil.isBlank(name) || value == null) {
            return false;
        }

        return true;
    }

     *
     * @param key       The key associated with the extractor. Must not be null or blank.
     * @param extractor The extractor to add. Must not be null.
     */
    public void addExtractor(final String key, final Extractor extractor) {
        if (StringUtil.isBlank(key)) {
            throw new CrawlerSystemException("The key is null.");
        }
        if (extractor == null) {

        final String url = urlQueue.getUrl();
        if (StringUtil.isBlank(url)) {
            if (logger.isDebugEnabled()) {
                logger.debug("URL is a blank: {}", url);
            }
            return false;
        }

        // check it in queue
        for (final UrlQueue<Long> urlInQueue : urlQueueList) {

     * @param regex The regular expression to match URLs.
     * @param client The CrawlerClient instance.
     */
    public void addClient(final String regex, final CrawlerClient client) {
        if (StringUtil.isBlank(regex)) {
            throw new CrawlerSystemException("A regular expression is null.");
        }
        if (client == null) {
            throw new CrawlerSystemException("CrawlerClient is null.");
        }

            if ("field".equals(qName)) {
                fieldName = attributes.getValue("name");
                if (StringUtil.isBlank(fieldName)) {
                    fieldName = null;
                }
                buffer.setLength(0);
            } else if ("list".equals(qName)) {

     * @param path The FTP path to check.
     * @return true if it matches, false otherwise.
     */
    boolean matches(final String path) {
        if (StringUtil.isBlank(path)) {
            return false;
        }

        try {
            final int pos = path.indexOf('/', 6);
            final URI uri = new URI(pos == -1 ? path : path.substring(0, pos));

        final UrlQueue<?> urlQueue = CrawlingParameterUtil.getUrlQueue();
        if (urlQueue == null) {
            return;
        }

        final String url = urlQueue.getUrl();
        if (StringUtil.isBlank(url) || url.startsWith("file:")) {
            // not target
            return;
        }

        try {
            final URI uri = new URI(url);
            final String host = uri.getHost();

     * @param filename The filename to normalize.
     * @return The normalized filename.
     */
    protected String normalizeFilename(final String filename) {
        if (StringUtil.isBlank(filename)) {
            return filename;
        }
        final StringBuilder buf = new StringBuilder(filename.length() + 10);
        for (int i = 0; i < filename.length(); i++) {