In this chapter, we have given a quick presentation of the ideas driving REST and the REST client modules. The RESTful HTTP way of dealing with uncovering functionality is unique. We have seen the different libraries of REST client functions. First, we saw what RestTemplate is and its implementation in an Android application. Now, we know about the constructors of RestTemplate and its functionalities. Furthermore, we have learned about Retrofit, allowing us to actualize Retrofit in an Android application. We have also seen the utilization of its functionalities. Lastly, we look at how to implement Retrofit to get data from a REST API.

In the following chapters, we will develop a total project, including security, authorization/authentication, a database, and a custom REST API, with the Spring and Android application to deal with the API as a client. In these chapters, you will explore the full usage of the API and prepare to figure out how to make an API for a server and recover it from the client.