In the SpringSource training course for Groovy & Grails, we highlight that Grails stands on the shoulders of giants. One of those giants is Spring. Without it, Grails simply wouldn't have been developed as quickly as it was. It probably wouldn't have the flexibility to integrate easily with enterprise Java systems either. Just look at the number of plugins available: many are based on Java libraries with Spring support.
In this post, I want to start by looking at how Grails uses Spring and then cover the various ways in which you can access that raw power and flexibility.