카테고리 엔티티

@Entity
@Getter @Setter
public class Category {

    @Id @GeneratedValue
    @Column(name = "category_id")
    private Long id;

    private String name;

    @ManyToMany
    @JoinTable(name = "category_item",
            joinColumns = @JoinColumn(name = "category_id"),
            inverseJoinColumns = @JoinColumn(name = "item_id"))
    private List<Item> items = new ArrayList<>();

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "parent_id")
    private Category parent;

    @OneToMany(mappedBy = "parent")
    private List<Category> child = new ArrayList<>();

    /**
     * 연관 관계 메서드
     */
    public void addChildCategory(Category child) {
        this.child.add(child);
        child.setParent(this);
    }
}