Este projeto contém as partes básicas de uma api Rest usando JAVA, SPRING BOOT, HYBERNATE e H2
This project is meant to be a brief example of how the structure of a API should be.
Application is the main class of the project.
CONTROLLER LAYER We have a package named controller, where resides all the controllers of the application. In this project we've a class called Employee controller, which is a class with the @RestController annotation that tells the Spring that this class is responsible for handling HTTP Requests related to the Employees. This controller also contains a dependency of an object type EmployeeServiceImpl, that will be detailed ahead. The controller has methods mapped to the most common HTTP Requests.
MODEL LAYER We also have a package named model which we locate all the Model classes. In this project we have a class called Employee that contains a annotation @Entity which tells the Spring that this class must be mapped to a table in the database.
REPOSITORY LAYER Next we have a package named repository that basically contains a interface called EmployeeRepository. This interface extends other interface from JPA Persistence API called JpaRepository which is responsible for making the CRUD methods available. The EmployeeRepository interface takes an @Repository annotation.
SERVICE LAYER And finally we have a package named service that contains two files. The first is an interface called EmployeeService, where all methods for saving and retrieving data will be described. A class named EmployeeServiceImpl that will have the implementation of all methods listed in the interface mentioned before. The EmployeeServiceImpl will take an annotation @Service to tell Spring that this class is a service provider and will also contain an EmployeeRepository instance automatically injected via dependency injection.
This API functions basically by responding a HTTP Request (GET or POST), which will be captured by the controller, and will call the service layer, that subsequently will call the repository layer.
So. Request: HTTP Request -> Controller -> Service layer -> Repository layer
Response: Repository layer -> Service layer -> Controller -> Response
source: https://www.geeksforgeeks.org/spring-boot-spring-data-jpa/?ref=rp