An API is a contract between the API provider and the API consumers. REST is one of the most popular API styles, mainly because of it being simple to use and easy to understand. The term REST stands for REpresentational State Transfer, which is an architectural style defined by Roy T. Fielding in his dissertation back in 2000.

Even though REST has been around for 18 years at the time of writing this book, there are still misconceptions of what a RESTful API is. According to Roy T. Fielding, many APIs that call themselves RESTful is not really RESTful. There are even people that think that being RESTful is just JSON over HTTP. For years, there have been debates around HATEOAS (short for Hypermedia As The Engine Of Application State). In this chapter, we will talk about these topics in depth, and so you will learn about the following:

• RESTful API characteristics
• RESTful API design procedure
• RESTful API implementation in Spring MVC
• RESTful API consuming
• RESTful API testing