In this chapter, we introduced you to new application requirements and then moved to some of the core reactive concepts. We looked at the Reactive Manifesto and reactive programming. We then moved our attention to Spring 5 and Spring Security 5, and touched on some of the new features in it, especially regarding reactive programming. We then looked briefly at Spring's reactive programming efforts by introducing you to Project Reactor. After that, we explored Spring Security in a bit more detail to refresh your thoughts on this subject. Finally, we closed this chapter by giving you an idea of how examples would be structured in this book and what coding practices we will be using.

You should now have a good grasp on reactive programming, and on Spring Security and how it works. You should also have a clear understanding of how to go through the rest of the chapters, especially the example code.