Spring Security OAuth provides support for using Spring Security with OAuth (1a) and OAuth2 using standard Spring and Spring Security programming models and configuration idioms.
Applying security to an application is not for the faint of heart, and OAuth is no exception. Before you get started, you're going to want to make sure you understand OAuth and the problem it's designed to address. There is good documentation at the OAuth site. You will also want to make sure you understand how Spring and Spring Security work.
You're going to want to be quite familiar with both OAuth (and/or OAuth2) and Spring Security, to maximize the effectiveness of this developers guide. OAuth for Spring Security is tightly tied to both technologies, so the more familiar you are with them, the more likely you'll be to recognize the terminology and patterns that are used.