Spring boot - blog application (REST API) : Comment

 

Creating JPA "Comment" Entity

 

Comment

@Data
@NoArgsConstructor
@AllArgsConstructor

@Entity
@Table(name = "comments")
public class Comment 
{
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Long id;
	
	private String body;
	private String email;
	private String name;
	
	@ManyToOne(fetch =FetchType.LAZY)
	@JoinColumn(name="post_id", nullable=false)
	private Post post;

}

@ManyToOne(fetch =FetchType.LAZY)
@JoinColumn(name="post_id", nullable=false)
private Post post;

 

 

FetchType.LAZY

Hibernate to only Fetch the related entities from the database

when you use the relationship

 

@JoinColumn(name="post_id", nullable=false)

외래키 명 : post_id

 

실행 결과

Hibernate: create table comments (id bigint not null auto_increment, body varchar(255), email varchar(255), name varchar(255), post_id bigint not null, primary key (id)) engine=InnoDB
Hibernate: alter table comments add constraint FKh4c7lvsc298whoyd4w9ta25cr foreign key (post_id) references posts (id)

mysql

---

Post

@Data // getter setter requiredArgsConstructor toString
@NoArgsConstructor
@AllArgsConstructor

@Entity
@Table(name="posts", uniqueConstraints = {@UniqueConstraint(columnNames= {"title"})})
public class Post 
{
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	private Long id;
	
	@Column(name="title", nullable=false)
	private String title;
	
	@Column(name="description", nullable=false)
	private String description;
	
	@Column(name="content", nullable=false)
	private String content;
	
	@OneToMany(mappedBy="post", cascade= CascadeType.ALL, orphanRemoval= true)
	private Set<Comment> comments = new HashSet<>();
	
}

@OneToMany(mappedBy="post", cascade= CascadeType.ALL, orphanRemoval= true)
private Set<Comment> comments = new HashSet<>();

 

 

cascade는 Entity의 상태가 변화했을 때 관계가 있는 Entity에도 상태 변화를 전파시키는

orphanRemoval=true는 관계가 끊어진 child를 자동으로 제거

 

참고 : Cascade 이해 및 orphanRemoval=true vs CascadeType.REMOVE

 

 

---

 

Creating JPA Repository

public interface CommentRepository extends JpaRepository<Comment, Long>
{

}

 

※ SimpleJpaRepository 에 @Repository 애노테이션이 선언돼있기 때문에 CommentRepository 위에 애노테이션을 선언할 필요가 없다.

 

@Repository
@Transactional(readOnly = true)
public class SimpleJpaRepository<t, id=""> implements JpaRepositoryImplementation<t, id=""> { .. }</t,></t,>

 

 

---

 

Creating Comment DTO

Create CommentDTO class to send the data between client and server.

@Data
public class PostDto 
{
	private long id;
	private String title;
	private String description;
	private String content;
}

 

 

---

 

CRUD

Create Comment

Service

public interface CommentService 
{
	CommentDto createComment(long postId, CommentDto commentDto);
}

ServiceImpl

@Service
public class CommentServiceImpl implements CommentService
{
	private CommentRepository commentRepository;
	private PostRepository postRepository;
	
	@Autowired
	public CommentServiceImpl(CommentRepository commentRepository, PostRepository postRepository) {
		super();
		this.commentRepository = commentRepository;
		this.postRepository = postRepository;
	}


	@Override
	public CommentDto createComment(long postId, CommentDto commentDto) {
		
		// retrieve post entity by id
		Post post = postRepository.findById(postId).orElseThrow(() -> new ResourceNotFoundException("Post", "id", postId));
		
		// set Post to comment entity
		Comment comment = mapToEntity(commentDto);
		comment.setPost(post);

		// comment entity to DB
		Comment newComment = commentRepository.save(comment);
		
		return mapToDTO(newComment);
	}
	
	private CommentDto mapToDTO(Comment comment)
	{
		CommentDto commentDto = new CommentDto();
		commentDto.setId(comment.getId());
		commentDto.setName(comment.getName());
		commentDto.setEmail(comment.getEmail());
		commentDto.setBody(comment.getBody());
		return commentDto;
	}
	private Comment mapToEntity(CommentDto commentDto)
	{
		Comment comment = new Comment();
		comment.setId(commentDto.getId());
		comment.setName(commentDto.getName());
		comment.setEmail(commentDto.getEmail());
		comment.setBody(commentDto.getBody());
		return comment;
	}
}

mapToDTO, mapToEntity 추가

 

Controller

@RestController
@RequestMapping("/api")
public class CommentController 
{
	private CommentService commentService;

	public CommentController(CommentService commentService) {
		super();
		this.commentService = commentService;
	}
	
	@PostMapping("/posts/{postId}/comments")
	public ResponseEntity<CommentDto> createComment(
                    @PathVariable long postId,
                    @RequestBody CommentDto commentDto){
        	return new ResponseEntity<>(commentService.createComment(postId, commentDto), HttpStatus.CREATED);
	}
}

 

TEST

post man

 

 

MySQL

---

 

Gat All Comments By Post Id

Service 

	List<CommentDto>  getCommentsByPostId(long postId);

ServiceImpl

	@Override
	public List<CommentDto> getCommentsByPostId(long postId) 
	{
		List<Comment> comments = commentRepository.findByPostId(postId);
		
		return comments.stream().map(comment -> mapToDTO(comment)).collect(Collectors.toList());
	}

 

CommentRepository

public interface CommentRepository extends JpaRepository<Comment, Long>
{

	List<Comment> findByPostId(long postId);

}

 

Controller

	// get all comments by postid
	@GetMapping("/posts/{postId}/comments")
	public List<CommentDto> getCommentsByPostId(@PathVariable Long postId){
		return commentService.getCommentsByPostId(postId);
	}

 

TEST

http://localhost:8080/api/posts/2/comments

Post id 가 2인 모든 Comment

 

---

Get Comment By Id

Service

	CommentDto getCommentById(Long postId, Long commentId);

ServiceImpl

	@Override
	public CommentDto getCommentById(Long postId, Long commentId) {
		Post post = postRepository.findById(postId).orElseThrow(
				()-> new ResourceNotFoundException("Post", "id", postId));
		
		Comment comment =commentRepository.findById(commentId).orElseThrow(
				()-> new ResourceNotFoundException("Comment", "id", commentId));
		
		if(!post.getId().equals(comment.getPost().getId())) {
			throw new BlogAPIException(HttpStatus.BAD_REQUEST	, "Comment does not belong to post");
		}
		
		return mapToDTO(comment);
	}

 

Exception 추가

비지니스 로직이나 유효성 검사시 예외 처리

//whenever we write some business logic or validate request parameters
public class BlogAPIException extends RuntimeException
{
	private HttpStatus status;
	private String message;
	
	
	public BlogAPIException(String message, HttpStatus status, String message2) {
		super(message);
		this.status = status;
		message = message2;
	}

	public BlogAPIException(HttpStatus status, String message) {
		super();
		this.status = status;
		this.message = message;
	}

	public HttpStatus getStatus() {
		return status;
	}

	@Override
	public String getMessage() {
		return message;
	}
}

 

 

Controller

	@GetMapping("/posts/{postId}/comments/{commentId}")
	public ResponseEntity<CommentDto> getCommentById(@PathVariable Long postId, @PathVariable Long commentId){
		return new ResponseEntity<>(commentService.getCommentById(postId, commentId), HttpStatus.OK);
	}

 

TEST

 

Comment 값은 있는데

게시물에 해당 Comment가 없을 경우

http://localhost:8080/api/posts/1/comments/1

사용자 정의 예외 (BlogAPIException) 발생

---

Comment 값도 없고

게시물에 해당 Comment가 없을 경우

사용자 정의 예외 (ResourceNotFoundException) 발생

 

---

Update Comment By Id 

수정하기

CommentService

	CommentDto updateComment(Long postId, long commentId, CommentDto commentRequest);

CommentServiceImpl

	@Override
	@Transactional
	public CommentDto updateComment(Long postId, long commentId, CommentDto commentRequest) {
		
		Post post = postRepository.findById(postId).orElseThrow(
				()-> new ResourceNotFoundException("Post", "id", postId));
		
		Comment comment =commentRepository.findById(commentId).orElseThrow(
				()-> new ResourceNotFoundException("Comment", "id", commentId));
		
		if(!post.getId().equals(comment.getPost().getId())){
			throw new BlogAPIException(HttpStatus.BAD_REQUEST,"Comment does not belongs to post");
		}
		
		comment.setName(commentRequest.getName());
		comment.setEmail(commentRequest.getEmail());
		comment.setBody(commentRequest.getBody());
		
		return mapToDTO(comment);
	}

CommentController

	@PutMapping("/posts/{postId}/comments/{id}")
	public ResponseEntity<CommentDto> updateComment(@PathVariable Long postId, @PathVariable(value="id") Long commentId, 
					@RequestBody CommentDto commentDto)
	{
		return new ResponseEntity<>(commentService.updateComment(postId, commentId, commentDto), HttpStatus.OK);
	}

 

TEST

post man

 

STS 콘솔창에서 update 쿼리가 나가는 것을 확인

Hibernate: select comment0_.id as id1_0_0_, comment0_.body as body2_0_0_, comment0_.email as email3_0_0_, comment0_.name as name4_0_0_, comment0_.post_id as post_id5_0_0_ from comments comment0_ where comment0_.id=?
Hibernate: update comments set body=?, email=?, name=?, post_id=? where id=?

 

---

Delete Comment

Service

	void deleteComment(Long postId, long CommentId);

ServiceImpl

	@Override
	public void deleteComment(Long postId, long commentId) {
		Post post =  postRepository.findById(postId).orElseThrow(
				()-> new ResourceNotFoundException("Post", "id",postId	));
		
		Comment comment =commentRepository.findById(commentId).orElseThrow(
				()-> new ResourceNotFoundException("Comment", "id", commentId));
		
		if(!post.getId().equals(comment.getPost().getId())) {
			throw new BlogAPIException(HttpStatus.BAD_REQUEST, "Comment does not belongs to post");
		}
		
		commentRepository.delete(comment);
	}

 

Controller

	@DeleteMapping("/posts/{postId}/comments/{id}")
	public ResponseEntity<String> deleteComment(@PathVariable Long postId, @PathVariable(value="id") Long commentId)
	{
		commentService.deleteComment(postId, commentId);
		return new ResponseEntity<String>("Comment deleted Successfully", HttpStatus.OK);
	}

 

TEST

Hibernate: delete from comments where id=?