Tapestry Infodea explains it nicely. That was my working setup in T5 5.0.11. But I've just upgraded to 5.0.18, which has a newer version of Jetty and so as per Jetty website, I changed the jetty.env-xml configuration to add an extra scoping parameter:
<pre> <New id="medis" class="org.mortbay.jetty.plus.naming.Resource"> * <Arg>[scope]</Arg>* * * <Arg>jdbc/mydb</Arg> </pre> my setup now no longer works. :( Hope that's not overly unhelpful.