API in SpringBoot

• Related:
  • APIs
  • 🐣Spring & SpringBoot

public interface UserService {
    UserDto findById(Long id);
    void createUser(UserDto user);
    void deleteUser(Long id);
}

• UserService is the official interface (API) that can be used by controllers or external systems.
• The actual implementation is hidden in a different class, and the API contract remains the same even if the implementation is replaced.
• Related: Data Transfer Object (DTO)

The API structure

src
└── main
    └── java
        └── com.example.api
            ├── controller      # HTTP 요청 진입점 (REST API)
            ├── service         # 비즈니스 로직 API (interface)
            ├── repository      # DB 접근 API (Spring Data JPA 등)
            └── dto             # API 입출력 객체

• Even if you don’t use the interface keyword, a controller endpoint (e.g., @GetMapping) still functions as a type of API contract.
  • JPA (Java Persistence API) (in Spring)
    • Allows you to interact with the database w/o complex SQL queries
  • JDBC (Java Database Connectivity)
    • If you don’t want to use Spring, you use this (but not recommended)