Dependency injection removes the responsibility for object creation and object linking from the objects themselves to a factory. The factory is often provided by an Inversion of Control (IoC) container. For an overview of Inversion of Control containers and the Dependency Injection pattern, please see Martin Fowler’s article.
Internally, the framework uses its own dependency injection container that is very similar to Google Guice. Both were originally developed by Bob Lee. Plugins are available to integrate applications with other IoC containers (e.g. Spring Plugin, Plexus Plugin ). An application can even use a local copy of Google Guice for dependency injection needs.
Actions can still be instantiated via Spring configuration by way of the Spring Plugin, but Spring is entirely optional.