@Override
	public final void init(FilterConfig config) throws ServletException {
		final ServletContext ctx = config.getServletContext();
		final ZestManager oldManager = ZestManager.getManager(ctx);

		//prepare parser
		final Parser parser;
		String clsnm = config.getInitParameter("parser-class");
		parser = clsnm != null ?
			(Parser)newInstance(clsnm, Parser.class): new ParserImpl();

		//prepare manager
		clsnm = config.getInitParameter("manager-class");
		_manager = clsnm != null ?
			(ZestManager)newInstance(clsnm, ZestManager.class): new ZestManager();
		_manager.init(ctx, parser);

		if (oldManager != null)
			log.warning(oldManager+" is replaced"+_manager);
	}