如何使用Spring Security的Java Web应用程序使用自定义身份验证机制？

I'm working on a project to convert an existing Java web application to use Spring Web MVC. As a part of this I will migrate the existing log-on/log-off mechanism to use Spring Security. The idea at this stage is to replicate the existing functionality and replace only the web layer, leaving the service classes and objects in place. The required functionality is simple. Access is controlled to URLs and to access certain pages the user must log on. Authentication is performed with a simple username and password along with an extra static piece of information that comes from the login page. There is no notion of a role: once a user has logged on they have access to all of the pages. Behind the scenes, the service layer has a class with a simple authentication method:I'm working on a project to convert an existing