Developing software applications is hard enough even with good tools and technologies. Implementing applications using platforms which promise everything but turn out to be heavy-weight, hard to control and not very efficient during the development cycle makes it even harder. Spring provides a light-weight solution for building enterprise-ready applications, while still supporting the possibility of using declarative transaction management, remote access to your logic using RMI or web services, and various options for persisting your data to a database. Spring provides a full-featured MVC framework, and transparent ways of integrating AOP into your software.
Spring could potentially be a one-stop-shop for all your enterprise applications; however, Spring is modular, allowing you to use just those parts of it that you need, without having to bring in the rest. You can use the IoC container, with Struts on top, but you could also choose to use just the Hibernate integration code or the JDBC abstraction layer. Spring has been (and continues to be) designed to be non-intrusive, meaning dependencies on the framework itself are generally none (or absolutely minimal, depending on the area of use).
This document provides a reference guide to Spring's features. Since this document is still to be considered very much work-in-progress, if you have any requests or comments, please post them on the user mailing list or on the support forums at http://forum.springframework.org/.
Before we go on, a few words of gratitude are due to Christian Bauer (of the Hibernate team), who prepared and adapted the DocBook-XSL software in order to be able to create Hibernate's reference guide, thus also allowing us to create this one. Also thanks to Russell Healy for doing an extensive and valuable review of some of the material.