REST API 개선, JPA와 Hibernate를 이용해 H2에 연결

JPA를 사용해서 데이터베이스와 통신하기 위해 UserResource를 복사해서 UserJpaResource를 만들겠습니다.

UserJpaResource

• UserRepository를 사용합니다.
• service → repositoy로 변경합니다.

package study.rest.webservices.restfulwebservices.user;

import jakarta.validation.Valid;
import org.springframework.hateoas.EntityModel;
import org.springframework.hateoas.server.mvc.WebMvcLinkBuilder;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
import study.rest.webservices.restfulwebservices.jpa.UserRepository;

import java.net.URI;
import java.util.List;
import java.util.Optional;

import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.linkTo;
import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.methodOn;

@RestController
public class UserJpaResource {
    private UserRepository repository;

    public UserJpaResource(UserRepository repository) {
        this.repository = repository;
    }

    //GET /users
    @GetMapping("/jpa/users")
    public List<User> retrieveAllUsers() {
        return repository.findAll();
    }

    //EntityModel
    //WebMvcLinkBuilder
    @GetMapping("/jpa/users/{id}")
    public EntityModel<User> retrieveUser(@PathVariable("id") int id) {
        Optional<User> user = repository.findById(id);

        if (user.isEmpty()) {
            throw new UserNotFoundException("id:" + id);
        }

        EntityModel<User> entityModel = EntityModel.of(user.get());
        WebMvcLinkBuilder link = linkTo(methodOn(this.getClass()).retrieveAllUsers());
        entityModel.add(link.withRel("all-users"));

       return entityModel;
    }

    @DeleteMapping("/jpa/users/{id}")
    public void deleteUser(@PathVariable int id) {
        repository.deleteById(id);
    }

    //POST /users
    @PostMapping("/jpa/users")
    public ResponseEntity<User> createUser(@Valid @RequestBody User user) {
        User savedUser = repository.save(user);
        URI location = ServletUriComponentsBuilder.fromCurrentRequest()
                .path("{id}")
                .buildAndExpand(savedUser.getId())
                .toUri();
        return ResponseEntity.created(location).build();
    }
}