}
    }

    public void addExtractor(final List<String> keyList, final Extractor extractor) {
        if (keyList == null || keyList.isEmpty()) {
            throw new CrawlerSystemException("The key list is empty.");
        }
        for (final String key : keyList) {
            addExtractor(key, extractor);
        }
    }

    public Extractor getExtractor(final String key) {

public abstract class AbstractExtractor implements Extractor {

    @Resource
    protected CrawlerContainer crawlerContainer;

    public void register(final List<String> keyList) {
        getExtractorFactory().addExtractor(keyList, this);
    }

    protected MimeTypeHelper getMimeTypeHelper() {
        final MimeTypeHelper mimeTypeHelper = crawlerContainer.getComponent("mimeTypeHelper");