Reactive programming is one of the most important features of Spring Framework 5.0.

Microservices architectures are typically built around event-based communication. Applications are built to react to events (or messages).

Reactive programming provides an alternate style of programming focused on building applications that react to events.

While Java 8 does not have built-in suppport for reactive programming, there are a number of frameworks that provide support for reactive programming:

• Reactive Streams: Language-neutral attempt to define reactive APIs.
• Reactor: Java implementation of Reactive Streams provided by the Spring Pivotal team.
• Spring WebFlux: Enables the development of web applications based on reactive programming. Provides a programming model similar to Spring MVC.

We will discuss Reactive Programming and how you can implement it with Spring Web Flux in Chapter 11, Reactive Programming.