* including content extraction, metadata processing, and robots tag handling.
 */
public class FessXpathTransformer extends XpathTransformer implements FessTransformer {

    /** Logger instance for this class */
    private static final Logger logger = LogManager.getLogger(FessXpathTransformer.class);

    /** HTTP header name for robots tag */
    private static final String X_ROBOTS_TAG = "X-Robots-Tag";

        fessXpathTransformer.convertUrlMap.put("feed:", "http:");

        assertEquals("", fessXpathTransformer.removeCommentTag(""));
        assertEquals(" ", fessXpathTransformer.removeCommentTag("<!-- - -->"));
        assertEquals("abc", fessXpathTransformer.removeCommentTag("abc"));
        assertEquals("abc ", fessXpathTransformer.removeCommentTag("abc<!-- foo -->"));