如何禁用Jetty的WebAppContext的目录列表?

I'm embedding Jetty (version 7.4.5.v20110725) into a java application. I'm serving JSP pages in ./webapps/jsp/ using Jetty's WebAppContext, but if I visit localhost:8080/jsp/ I get Jetty's directory listing for the entire contents of ./webapps/jsp/. I've tried setting the dirAllowed parameter to false on the WebAppContext and it does not change the directory listing behavior.I'm embedding Jetty (version 7.4.5.v20110725) i