The main purpose of Hypermedia As The Engine Of Application State (HATEOAS) is to decouple the server (the service provider) from the client (the service consumer). The server provides the client with information on other possible actions that can be performed on the resource. 

Spring HATEOAS provides a HATEOAS implementation, especially for the REpresentational State Transfer (REST) services implemented with Spring MVC.

Spring HATEOAS has the following important features:

• A simplified definition of links pointing to service methods, making the links less fragile
• Support for JSON and JAXB (XML-based) integration
• Support for hypermedia formats such as Hypertext Application Language (HAL)

In the next section, we will understand the mechanism of Spring's IoC container.