This is what worked for me:
1. Change %CATALINA_HOME%\bin\startup.bat add the following line:
SET CATALINA_OPTS=-server -Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
and run this startup.bat, you should see this line at the top of output:
Listening for transport dt_socket at address: 8000
2. In Eclipse configure it like this:
Now press Debug button. Place a breakpoint somewhere in the code and you are done!