Start script customization - where to put template files

I’m working on a Java application that builds up its class path at runtime and should simply be started as a jar file, that is:

java -jar MyApp.jar

I’d like to modify the start scripts generated by the “application” plugin to start my application this way. From the docs I came up with code like the following in my “build.gradle”:

task createStartScripts(type: CreateStartScripts) {
  unixStartScriptGenerator.template = resources.text.fromFile('customUnixStartScript.txt')
  windowsStartScriptGenerator.template = resources.text.fromFile('customWindowsStartScript.txt')

Sadly, this does not work. No matter where I place my template files they are ignored without any error or warning message.

Does anybody know, what I’m doing wrong here?