temp.java

@Getter
@NoArgsConstructor
@Entity
public class User {

    @OneToMany(mappedBy = "user", fetch = FetchType.LAZY)
    private List<PartyUser> parties = new ArrayList<>();
}


@Getter
@NoArgsConstructor
@Entity
public class Party {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "leader_id")
    private User leader;

    @OneToMany(mappedBy = "party", fetch = FetchType.LAZY)
    private List<PartyUser> users = new ArrayList<>();
  
}


@NoArgsConstructor
@Getter
@Entity
@Table(
        name="party_user",
        uniqueConstraints={
                @UniqueConstraint(
                        columnNames={"user_id","party_id"}
                )
        }
)
public class PartyUser extends BaseTimeEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @JoinColumn(name = "user_id")
    private User user;

    @ManyToOne
    @JoinColumn(name = "party_id")
    private Party party;

    @Builder
    public PartyUser(User user, Party party) {
        this.user = user;
        this.party = party;
    }
}


// party dto 를 만들고 싶다면????
@Data
public class PartyResponseDto {
    private final long id;
    private final String title;
    private final String body;

    public PartyResponseDto(Party entity) {
        id = entity.getId();
        title = entity.getTitle();
        body = entity.getBody();
        // TODO: 세상에... Party 가 User 대신 필요도 없는 PartyUser 를 가져온다... User 를 가져오려면 어떻게 해야됨??
    }
}