What you have to do is to enable the debugger for JVM running your web application, that has nothing to see with JBPM :^0 . Let's check the right place to parse following property to your JVM
-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=8000
In case you trigger your app via Maven plugin, i am almost sure that the plugin provides a way to init debugger infrastructure. Let's take the case of Maven Surefire plugin, you could enable debugger with mvn clean instal -Dmaven.surefire.debug=true