The cometd plugin works fine on development environment. But After I deploy it to tomcat (6.0.18), the application fail to start. it complains not able to find the class org/mortbay/util/ajax/JSON$Source.class. So I have to download the jar jetty-util-6.1.14.jar and put it in the lib dir. then rebuild and deploy and it works. So please just add jetty-util-6.1.14.jar to cometd plugin at next release.