RESTful APIs are present in most modern applications we use every day, from reading Twitter messages or visiting Facebook pages to reading our emails or doing a Google search. With a lightweight communication protocol and an emphasis on resources, states, and verbs, they have become a natural language for the interchange of information through the HTTP protocol.

In this chapter, we will understand how we can create our own RESTful APIs using Kotlin and the Spring framework. We will learn how we can receive parameters, and how HTTP verbs and status will make our APIs define their ubiquitous language. We spoke about a ubiquitous language in our Domain-Driven Design section in Chapter 1, Understanding Microservices.

Furthermore, we will learn how to handle JSON requests and responses in our APIs. And finally, we will review how Spring allows us to handle...