게시물 생성 API 구현하기

게시물을 등록하는 코드를 작성하겠습니다.

게시물 전체조회와 마찬가지로 UserJpaResource에 작성하겠습니다.

UserJpaResource

• createPostForUser()

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.PostRepository;
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;
    private PostRepository postRepository;

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

    //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("id") int id) {
        repository.deleteById(id);
    }

    @GetMapping("/jpa/users/{id}/posts")
    public List<Post> retrievePostsForUser(@PathVariable("id") int id) {
        Optional<User> user = repository.findById(id);

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

    //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();
    }

    @PostMapping("/jpa/users/{id}/posts")
    public ResponseEntity<Object> createPostForUser(@PathVariable("id") int id, @Valid @RequestBody Post post) {
        Optional<User> user = repository.findById(id);

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

        post.setUser(user.get());
        Post savedPost = postRepository.save(post);

        URI location = ServletUriComponentsBuilder.fromCurrentRequest()
                .path("/{id}/posts")
                .buildAndExpand(savedPost.getId())
                .toUri();

        return ResponseEntity.created(location).build();
    }
}

• user가 없다면 에러를 발생시킵니다.
• 있다면 user를 post 엔티티에 저장합니다.
• 저장된 post 엔티티의 아이디를 현재 URI의 뒤에 붙인 다음 반환합니다.
• 예) 저장된 post의 아이디가 1이라면 localhost:8080/jpa/users/10001/posts/1 을 반환합니다.