Building a Reactive Web Application

We began our journey by exploring some of the basics of the Spring Framework and its module system in Chapter 1, Creating an Application to List World Countries with their GDP. Let's leave all the new and advanced topics of Spring Framework for now and, in this chapter, look at one of the most popular topics: how to make highly scalable and responsive applications by adopting a reactive paradigm. 

The world of technology is migrating from blocking, synchronous, and thread-driven implementation to non-blocking, asynchronous, and event-based systems, which are resilient and capable of managing a very large volume of data with a consistent response time. This is the core concern addressed by a reactive system.

From the perspective of the programming model, Reactive Programming has influenced the paradigm shift from...