如何在现有Java EE应用程序上开始使用GRAILS？

I'm new to grails. I'd like to give it a whirl by implementing a new feature or two into an existing Java EE application. The current Java EE app is a fairly standard Spring MVC/Hibernate app running on Tomcat. Looking through the documentation, it looks like I should be able to leverage all of the current business logic that's written in Java. I'm new to grails. I'd like to give it a whirl