I just moved from Netbeans to Eclipse. In Netbeans, I can debug Playframework applications out of the box. However, in Eclipse, it seems hard to configure this in order to debug
Play 2.1-RC2 : Running Play! app that is synced with Eclipse
To make the project Eclipse compatible, got he project folder and then give command ">play eclipse". Now you can add it as an existing project form eclipse.
Then to run it you have to first run start play in the project folder i.e. command "play"
This will activate play server and identify the app in the project i.e. [appname]$ now you have to just give the command "run" to see your app running on the localhost:9000 or whichever port config you have specified.
Debug mode: To run this similarly you need first give command "play" then [appname]$ "play debug run" this will by default use port 9999 so when you go to localhost:9000 in your browser and in your eclipse file -> Debug As -> Debug configuration.. -> New Remote Java Application -> connect specify port 9999 and debug