This chapter reviewed the major and minor changes that you will find when upgrading an existing Spring Security 3 project to Spring Security 4.2. In this chapter, we have reviewed the significant enhancements to the framework that are likely to motivate an upgrade. We also examined upgrade requirements, dependencies and common types of code, and configuration changes that will prevent applications from working post-upgrade. We also covered investigation (at a high level) of the overall code-reorganization changes that the Spring Security authors made as part of codebase restructuring.
If this is the first chapter you've read, we hope that you return to the rest of the book and use this chapter as a guide to allow your upgrade to Spring Security 4.2 to proceed as smoothly as possible!