[스프링 부트] 34. 연관 관계가 있는 엔티티 삭제 구현 - 웹 게시판 v6

Reply 엔티티

@NoArgsConstructor(access = AccessLevel.PROTECTED)
@Getter
@Table(name = "reply_tb")
@Entity
public class Reply {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String comment;

    @ManyToOne(fetch = FetchType.LAZY)
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    private Board board;

    @CreationTimestamp
    private Timestamp createdAt;

    @Builder
    public Reply(Integer id, String comment, User user, Board board, Timestamp createdAt) {
        this.id = id;
        this.comment = comment;
        this.user = user;
        this.board = board;
        this.createdAt = createdAt;
    }
}

Board 엔티티

@NoArgsConstructor(access = AccessLevel.PROTECTED)
@Getter
@Table(name = "board_tb")
@Entity
public class Board {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String title;
    private String content;
    
    @ManyToOne(fetch = FetchType.LAZY)
    private User user;

    @OneToMany(mappedBy = "board", fetch = FetchType.LAZY, cascade = CascadeType.REMOVE, orphanRemoval = true)
    private List<Reply> replies; 

    @CreationTimestamp
    private Timestamp createdAt;
   
    @Builder
    public Board(Integer id, String title, String content, User user, Timestamp createdAt) {
        this.id = id;
        this.title = title;
        this.content = content;
        this.user = user;
        this.createdAt = createdAt;
    }
}

BoardResponseDTO

public class BoardResponse {
    @Data
    public static class DetailDTO {
        private int id;
        private String title;
        private String content;
        private String createdAt;

        private Integer userId;
        private String username;
        private boolean isOwner = false;

        private List<ReplyDTO> replies;

        @Data
        class ReplyDTO {
            private int id;
            private String comment;
            private int userId; 
            private String username;
            private boolean isOwner = false; // 이너클래스라 변수 이름이 같아도 된다.

            public ReplyDTO(Reply reply, User sessionUser) {
                this.id = reply.getId();
                this.comment = reply.getComment();
                this.userId = reply.getUser().getId();
                this.username = reply.getUser().getUsername();
                if (sessionUser != null) {
                    this.isOwner = sessionUser.getId().equals(reply.getUser().getId());
                }
            }
        }

        public DetailDTO(Board board, User sessionUser) {
            this.id = board.getId();
            this.title = board.getTitle();
            this.content = board.getContent();
            this.createdAt = MyDate.formatToStr(board.getCreatedAt());

            this.userId = board.getUser().getId();
            this.username = board.getUser().getUsername();
            if (sessionUser != null) {
                this.isOwner = sessionUser.getUsername().equals(board.getUser().getUsername());
            }
            this.replies = board.getReplies().stream().map(r -> new ReplyDTO(r, sessionUser)).toList();
        }
    }
}

if (sessionUser != null) {
    this.isOwner = sessionUser.getId().equals(reply.getUser().getId());
}

• 세션에 저장된 User 정보와 Reply(댓글)를 작성한 User 정보를 비교합니다.

• Integer 비교는 ‘==’ 이 아니라 .equals로 해야 합니다.
• int와 달리 Integer는 객체의 참조를 비교합니다.
• 값이 아닌 메모리 주소를 비교하므로, 동일한 값을 가진 다른 객체는 false를 반환할 수 있습니다.

BoardRepository

@RequiredArgsConstructor
@Repository
public class BoardRepository {

    private final EntityManager em;   

    public void delete(int id) {
        em.createQuery("delete from Board b where id = :id")
                .setParameter("id", id)
                .executeUpdate();
    }
}

BoardService

@Transactional(readOnly = true)
@RequiredArgsConstructor
@Service
public class BoardService {

    private final BoardRepository boardRepository;


    @Transactional
    public void 게시글삭제(int id, User sessionUser) {
        Board boardPS = boardRepository.findById(id)
                .orElseThrow(() -> new Exception404("게시글 아이디를 찾을 수 없습니다."));

        if (!sessionUser.getId().equals(boardPS.getUser().getId())) {
            throw new Exception403("권한이 없습니다.");
        }
        boardRepository.delete(id);
    }
}

BoardController

@RequiredArgsConstructor
@Controller
public class BoardController {

    private final BoardService boardService;
    private final HttpSession session;

    // 메인화면 이동
    @GetMapping("/")
    public String list(Model model) { 
        List<BoardResponse.DTO> boardList = boardService.게시글목록보기();
        model.addAttribute("models", boardList);
        return "index";
    }

    // 글 삭제
    @PostMapping("/board/{id}/delete")
    public String delete(@PathVariable("id") int id) {
        User sessionUser = (User) session.getAttribute("sessionUser");
        boardService.게시글삭제(id, sessionUser);
        return "redirect:/";
    }
}

삭제 구현 방법

1. FK에 @OnDelete 설정 걸기

@OnDelete(action = OnDeleteAction.CASCADE)
@ManyToOne(fetch = FetchType.LAZY)
private Board board;

• @OnDelete(action = OnDeleteAction.CASCADE)
• 부모 엔티티(Board)가 삭제될 때 종속된 자식 엔티티(Reply)도 함께 삭제되도록 설정합니다.

2. Reply 삭제 메서드 추가

public void deleteAll(int boardId){
    Query q = em.createQuery("delete from Reply r where r.board.id=:boardId");
    q.setParameter("boardId", boardId);
    q.executeUpdate();
}

3. Reply의 외래키를 null로 설정

public void updateNull(int boardId){
    Query q = em.createQuery("update Reply r set r.board.id=null where r.board.id=:boardId");
    q.setParameter("boardId", boardId);
    q.executeUpdate();
}

4. 외래키를 설정하지만 제약 조건은 비활성화

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "board_id", foreignKey = @ForeignKey(ConstraintMode.NO_CONSTRAINT)) // 외래 키 제약 조건 비활성화
private Board board;

5. Board를 논리 삭제

• Board에 visible 컬럼을 추가하고 삭제 시 false로 update합니다.