Grails is actually a Spring MVC application in disguise. Spring MVC is the Spring framework's built-in MVC web application framework. Although Spring MVC suffers from the same difficulties as frameworks like Struts in terms of its ease of use, it is superbly designed and architected and was, for Grails, the perfect framework to build another framework on top of.

Grails leverages Spring MVC in the following areas:

In other words Grails has Spring embedded running all the way through it.

The Grails ApplicationContext

Spring developers are often keen to understand how the Grails ApplicationContext instance is constructed. The basics of it are as follows.

Configured Spring Beans

Most of Grails' configuration happens at runtime. Each plug-in may configure Spring beans that are registered with the ApplicationContext. For a reference as to which beans are configured refer to the reference guide which describes each of the Grails plug-ins and which beans they configure.