JPA 저장은 ID, 조회는 객체로 사용하는법

Comment

@Getter
@Entity
@NoArgsConstructor(access = AccessLevel.PROTECTED)
public class Comment extends BaseEntity {

    private Long roomId;
    @Column(length = 500)
    private String comment;
    @ManyToOne(targetEntity = Member.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "member_id")
    private Member member;
    
    ...
}

---

Member

@Entity
@Getter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
public class Member extends BaseEntity {

    @NonNull
    private String username;
    @Embedded
    private Password password;
    @Embedded
    private Nickname nickname;
    
    ...
}

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저장  로직

public CommentResponse comment(final Long roomId, final Long memberId, final CommentRequest request) {
    validateExistRoom(roomId);
    Member member = memberRepository.getMemberById(memberId);

    Comment comment = new Comment(roomId, request.comment(), member);
    commentRepository.save(comment);

    return CommentResponse.of(comment);
}

Comment를 저장하기 위해서는 Member 객체가 필요하고 Member 객체를 가져오기위해서 MemberRepository에서 Member를 조회하는 쿼리가 필요하다.

create table comment
(
    id         bigint auto_increment,
    comment    varchar(500),
    member_id  bigint,
    room_id    bigint,
    created_at timestamp(6),
    updated_at timestamp(6),
    primary key (id),
    constraint fk_comment_member_id foreign key (member_id) references member (id)
)

그러나 실제 테이블을 고려할 때, Comment를 저장하는 데는 Member Id가 필요하지만 Member 객체가 필요하지 않습니다. 
Comment에 Member 필드를 Member Id로 변경하는 방법도 있지만 댓글을 조회할 때 Member의 NickName과 같은 필드가 필요합니다

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저장은 ID,  조회는 객체로 사용

@Getter
@Entity
@NoArgsConstructor(access = AccessLevel.PROTECTED)
public class Comment extends BaseEntity {

    private Long roomId;
    @Column(length = 500)
    private String comment;

    @ManyToOne(targetEntity = Member.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "member_id", insertable = false, updatable = false)
    private Member member;

    @Column(name = "member_id")
    private Long memberId;

    public Comment(final Long roomId, final String comment, final Long memberId) {
        this.roomId = roomId;
        this.comment = comment;
        this.memberId = memberId;
    }
    ...
}

public CommentResponse comment(final Long roomId, final Long memberId, final CommentRequest request) {
    validateExistRoom(roomId);
    
    Comment comment = new Comment(roomId, request.comment(), memberId);
    commentRepository.save(comment);

    return CommentResponse.of(comment);
}

 

insertable = false 및 updatable = false 설정을 사용하면 Comment를 저장할 때 Member 정보를 필요하지 않고 Member Id만을 사용하여 Comment와 Member를 연결할 수 있습니다.
위 방법으로 데이터베이스에 불필요한 업데이트 작업을 방지하고 Comment를 효율적으로 저장할 수 있습니다.

 

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https://stackoverflow.com/questions/27930449/jpa-many-to-one-relation-need-to-save-only-id