## start Jetty in debug mode
>java -Xdebug -agentlib:jdwp=transport=dt_socket,address=9999,server=y,suspend=n -jar start.jar

First line in console will be:
Listening for transport dt_socket at address: 9999

In eclipse, setup a new Debug Remote Java Application where,
 Project: %the project you have running in Jetty%
 Host: %host where jetty is running%
 Port: 9999