[JPA_Basic] ERD를 기반으로 한 Entity 작성

이 글은 김영한의 [자바 ORM 표준 JPA 프로그래밍 - 기본편]을 수강하며 정리한 글입니다.

 

👉 기본 환경

- Language: Java

- DB: H2 Database

- IDE: IntelliJ

 

 

ERD

 

 

Member Entity

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
 
@Entity
public class Member {
 
    @Id @GeneratedValue
    @Column(name = "MEMBER_ID")
    private Long id;
 
    private String name;
    private String city;
    private String street;
    private String zipcode;
 
    @OneToMany(mappedBy = "member")
    private List<Order> orders = new ArrayList<>();
 
}
 

 

 

Order Entity

import javax.persistence.*;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
 
@Entity
@Table(name = "ORDERS")
public class Order {
 
    @Id @GeneratedValue
    @Column(name = "ORDER_ID")
    private Long id;
 
    @ManyToOne
    @JoinColumn(name = "MEMBER_ID")
    private Member member;
 
    @OneToMany(mappedBy = "order")
    private List<OrderItem> orderItems = new ArrayList<>();
 
    @OneToOne
    @JoinColumn(name = "DELIVERY_ID")
    private Delivery delivery;
 
    private LocalDateTime orderDate;
 
    @Enumerated(EnumType.STRING)
    private OrderStatus status;
 
}
 

- @ManyToOne + @JoinColumn

    - 다대일 관계에서 다의 위치가 연관관계 주인

 

- @OneToMany(mappedBy)

    - 일대다 관계에서 일의 위치가 조회를 위한 임의 매핑

 

- @OneToOne

   - 일대일 관계에서 연관관계 주인은 상황에 따라 선택 가능

 

- @Enumerated(EnumType.STRING)

    - enum type 사용 시, @Enumerated type.STRING 지정 필수

 

 

Delivery Entity

import javax.persistence.*;
 
@Entity
public class Delivery {
 
    @Id @GeneratedValue
    @Column(name = "DELIVERY_ID")
    private Long id;
 
    @OneToOne(mappedBy = "delivery")
    private Order order;
 
    private String city;
    private String street;
    private String zipcode;
 
    @Enumerated(EnumType.STRING)
    private DeliveryStatus status;
 
}
 

 

 

OrderItem Entity

import javax.persistence.*;
 
@Entity
public class OrderItem {
 
    @Id @GeneratedValue
    @Column(name = "ORDER_ITEM_ID")
    private Long id;
 
    @ManyToOne
    @JoinColumn(name = "ORDER_ID")
    private Order order;
 
    @ManyToOne
    @JoinColumn(name = "ITEM_ID")
    private Item item;
 
    @Column(name = "ORDER_PRICE")
    private int price;
    private int count;
 
}
 

 

 

Item Entity

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
 
@Entity
public class Item {
 
    @Id @GeneratedValue
    @Column(name = "ITEM_ID")
    private Long id;
 
    private String name;
    private int price;
    private int stockQuantity;
 
    @ManyToMany(mappedBy = "items")
    private List<Category> categories = new ArrayList<>();
 
}
 

- @ManyToMany

  ⭐ 관계형 데이터베이스에서 다대다 (Many-to-Many) 관계를 직접적으로 표현하는 것은 불가능

        ▶ 연결 테이블을 추가해서 일대다, 다대일 관계로 풀어내야 함

 

 

 

Category Entity

import javax.persistence.*;
import java.util.ArrayList;
import java.util.List;
 
@Entity
public class Category {
 
    @Id @GeneratedValue
    @Column(name = "CATEGORY_ID")
    private Long id;
 
    private String name;
 
    @ManyToOne
    @JoinColumn(name = "PARENT_ID")
    private Category parent;
 
    @OneToMany(mappedBy = "parent")
    private List<Category> children = new ArrayList<>();
 
    @ManyToMany
    @JoinTable(name = "CATEGORY_ITEM",
        joinColumns = @JoinColumn(name = "CATEGORY_ID"),
        inverseJoinColumns = @JoinColumn(name = "ITEM_ID")
    )
    private List<Item> items = new ArrayList<>();
}
 

- private Category parent

- private List<Category> children = new ArrayList<>()

    - 한 카테고리가 다른 카테고리를 부모로 가지는 계층 구조를 표현

    - 부모 : 자식 = 일 : 다

 

- @JoinTable

    - CATEGORY와 ITEM의 PK로 이뤄진 연결 테이블 생성

    - joinColumns

        - 현재 엔티티(Category)와 연결되는 외래키

    - inverseJoinColumns

        - 상대 엔티티(Item)와 연결되는 외래키

 

 

실행 결과

Hibernate: 
    
    create table Category (
       CATEGORY_ID bigint not null,
        name varchar(255),
        PARENT_ID bigint,
        primary key (CATEGORY_ID)
    )
 
Hibernate: 
    
    create table CATEGORY_ITEM (
       CATEGORY_ID bigint not null,
        ITEM_ID bigint not null
    )
 
Hibernate: 
    
    create table Delivery (
       DELIVERY_ID bigint not null,
        city varchar(255),
        status varchar(255),
        street varchar(255),
        zipcode varchar(255),
        primary key (DELIVERY_ID)
    )
 
Hibernate: 
    
    create table Item (
       ITEM_ID bigint not null,
        name varchar(255),
        price integer not null,
        stockQuantity integer not null,
        primary key (ITEM_ID)
    )
 
Hibernate: 
    
    create table Member (
       MEMBER_ID bigint not null,
        city varchar(255),
        name varchar(255),
        street varchar(255),
        zipcode varchar(255),
        primary key (MEMBER_ID)
    )
 
Hibernate: 
    
    create table OrderItem (
       ORDER_ITEM_ID bigint not null,
        count integer not null,
        price integer not null,
        ITEM_ID bigint,
        ORDER_ID bigint,
        primary key (ORDER_ITEM_ID)
    )
 
Hibernate: 
    
    create table ORDERS (
       ORDER_ID bigint not null,
        orderDate timestamp,
        status varchar(255),
        DELIVERY_ID bigint,
        MEMBER_ID bigint,
        primary key (ORDER_ID)
    )
 
 
 
Hibernate: 
    
    alter table Category 
       add constraint FK8tepc1qkmluodspg6tnliwhit 
       foreign key (PARENT_ID) 
       references Category
 
Hibernate: 
    
    alter table CATEGORY_ITEM 
       add constraint FKf1uerpnmn49vl1spbbplgxaun 
       foreign key (ITEM_ID) 
       references Item
 
Hibernate: 
    
    alter table CATEGORY_ITEM 
       add constraint FKjip0or3vemixccl6vx0kluj03 
       foreign key (CATEGORY_ID) 
       references Category
 
Hibernate: 
    
    alter table OrderItem 
       add constraint FKabge9eqalspcejij53rat7pjh 
       foreign key (ITEM_ID) 
       references Item
 
Hibernate: 
    
    alter table OrderItem 
       add constraint FKk7lmf97wukpquk6d8blxy5neq 
       foreign key (ORDER_ID) 
       references ORDERS
 
Hibernate: 
    
    alter table ORDERS 
       add constraint FKdbs21f1yi0coxy9y0kxw4g9jf 
       foreign key (DELIVERY_ID) 
       references Delivery
 
Hibernate: 
    
    alter table ORDERS 
       add constraint FKh0db7kqr88ed8hqtcqw3jkcia 
       foreign key (MEMBER_ID) 
       references Member