初学者向高手请教

Question

contextPath = getServletContext().getRealPath("/") + "test";
System.out.println(contextPath);
CometEngine cometEngine = CometEngine.getEngine();                
cometContext = cometEngine.register(contextPath); 
cometContext.setExpirationDelay(20*1000); 
String username = request.getParameter("username");
String message = request.getParameter("message");
System.out.println(username + ":" + message);
CometRequestHandler handler = new CometRequestHandler();
handler.attach(response.getWriter());
cometContext.addCometHandler(handler);  ---出问题句
cometContext.notify(handler);
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只要加上这句，就有异常，去掉去掉就没了，请问一下彭总这句话问题在哪呢？
异常：Grizzly Comet hasn't been registered