What is Inversion of Control (IoC)?
Inversion of control is a way to handle dependencies of objects. For an overview of of Inversion of Control (also referred to now as Dependency Injection), please read Martin Fowler's article on IoC.
Spring as recommended IoC Container
Spring is, among other things, an Inversion of Control framework. As of WebWork 2.2, it is the recommended IoC container. A detailed description how Spring Integration works and how it is configured is found here.
Besides Spring, there are numerous other containers available for you to use, such as Pico or the (deprecated) integrated XWork IoC container.
WebWork/XWork integrated IoC Container
 | As of WebWork 2.2, the WebWork/XWork IoC container has been deprecated (though not removed) and the WebWork team recommends you use Spring for all your IoC needs |
In WebWork IoC, objects that are have their dependencies managed are called "components".