Reactive Systems in Java

Chapter 1. Reactive in a Nutshell

Reactive is an overloaded word. You may have searched for reactive with a search engine to understand what it’s all about. If you haven’t, no worries—you’ve saved yourself a lot of confusion. There are many reactive things: Reactive Systems, Reactive Programming, Reactive extensions, Reactive messaging. Every day new ones pop up. Are all these “reactives” the same reactive? Are they different?

These are the questions we are going to answer in this chapter. We are going to sneak a peek at the reactive landscape to identify and help you understand the various nuances of reactive, what they mean, the concepts associated with them, and how they relate to one another. Because yes, without spoiling too much, all these “reactives” are related.

Note

As noted in the preface, we use the noun Reactive, with an uppercase R, to aggregate all the various facets of the reactive landscape, such as reactive programming, reactive systems, reactive streams, and so on.

What Do We Mean by Reactive?

Let’s start at the beginning. Forget about software and IT for a few minutes, and use an old-fashioned approach. If we look for reactive in the Oxford English Dictionary, we find the following definition:

reactive (adjective)

Showing a response to a stimulus. 1.1 Acting in response to a situation rather than creating or controlling it. 1.2 Having a tendency to react chemically. 1.3 (Physiology) Showing an immune response to a specific antigen. 1.4 (Of a disease or illness) ...