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