How to shutdown server using Grails

Is it possible to shutdown the server from a WAR-deployed Grails application?

Use case: I'm using an application to perform some processing. When it's done, I want the computer to shutdown (it's running on AWS and I don't want to have it run for longer than needed).

(If there isn't, I'll just set a CPU usage threshold on the AWS monitor and close it down when it drops below a given threshold using AWS's tools, but I'd like a less hacky way of doing it please).