100년 뒤 개발자 한승규입니다.

이번엔 Map을 mapping 해본다.

이런 테이블이 있다고 해보자.

import jakarta.persistence.*;

import java.util.HashMap;
import java.util.Map;

@Entity
@Table(name = "book")
public class book {
    @Id
    private String id;
    private String title;
    private String content;
    @ElementCollection
    @CollectionTable(
            name = "book_prop",
            joinColumns = @JoinColumn(name="book_id")
    )
    @MapKeyColumn(name = "name")
    @Column(name = "value")
    private Map<String, String> props = new HashMap<>();

    protected book(){}

    public book(String id, String title, String content, Map<String, String> props) {
        this.id = id;
        this.title = title;
        this.content = content;
        this.props = props;
    }
    
    //getter... setter...
}

이렇게 @CollectionTable로 저장할 테이블을 지정을 해주고

Map에 들어간 데이터를 어떤 column에 넣어줄지 PK는 @MapKeyColumn에, 그냥 데이터는 @Column으로 지정을 해준다.

import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import jakarta.persistence.EntityTransaction;
import jakarta.persistence.Persistence;

import java.util.HashMap;
import java.util.Map;

public class book_main {

    public static void main(String[] args) {
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("jpabegin");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        EntityTransaction entityTransaction = entityManager.getTransaction();

        Map<String, String> props1 = new HashMap<>();
        Map<String, String> props2 = new HashMap<>();

        props1.put("name1", "value1");
        props1.put("name2", "value2");
        book book1 = new book("1", "이름", "내용", props1);
        book book2;

        try{
            entityTransaction.begin();
            entityManager.persist(book1);
            entityTransaction.commit();
        }catch(NullPointerException exception){
            throw new NullPointerException();
        }

        try{
            book2 = entityManager.find(book.class, "1");
        }catch(NullPointerException exception){
            throw new NullPointerException();
        }

        System.out.println("book: " + book2);
        System.out.println("props: " + book2.getProps());
    }
}

이렇게 추가를 하고 조회를 하면

정상 작동하는 것을 볼 수 있다.

늘 그렇듯이 이번엔 Embeddable 타입이다.

이런 테이블이 있다고 하고, 여기서 PropValue를 Embeddable로 만들 생각이다.

우선 Embeddable 타입을 먼저 작성한다.

import jakarta.persistence.Access;
import jakarta.persistence.AccessType;
import jakarta.persistence.Embeddable;

@Embeddable
@Access(AccessType.FIELD)
public class PropValue {
    private String value;
    private boolean enabled;

    public PropValue(String value, boolean enabled) {
        this.value = value;
        this.enabled = enabled;
    }

    protected PropValue () {}
	
    //getter...setter...
    
    @Override
    public String toString() {
        return "PropValue{" +
                "value='" + value + '\'' +
                ", enabled=" + enabled +
                '}';
    }
}

이렇게 항상 작성하던 @Embeddable을 작성하고

import jakarta.persistence.*;

import java.util.HashMap;
import java.util.Map;

@Entity
@Table(name = "book")
public class book2 {
    @Id
    private String id;
    private String title;
    private String content;
    @ElementCollection
    @CollectionTable(
            name = "book_prop",
            joinColumns = @JoinColumn(name = "book_id")
    )
    @MapKeyColumn(name = "name")
    private Map<String, PropValue> props = new HashMap<>();

	//getter...setter...
    
    @Override
    public String toString() {
        return "book2{" +
                "id='" + id + '\'' +
                ", title='" + title + '\'' +
                ", content='" + content + '\'' +
                ", props=" + props +
                '}';
    }
}

@MapKeyColumn을 이용해서 그랬던 것처럼 작성을 해준다.

여기에 Map의 타입에 <PK, @Embeddable>을 넣어서 작성해준다.

import jakarta.persistence.EntityManager;
import jakarta.persistence.EntityManagerFactory;
import jakarta.persistence.EntityTransaction;
import jakarta.persistence.Persistence;

import java.util.HashMap;
import java.util.Map;

public class book_main2 {

    public static void main(String[] args) {
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("jpabegin");
        EntityManager entityManager = entityManagerFactory.createEntityManager();
        EntityTransaction entityTransaction = entityManager.getTransaction();

        Map<String, PropValue> Propvalues = new HashMap<>();

        PropValue propValue1 = new PropValue("value1", true);
        PropValue propValue2 = new PropValue("value2", true);

        Propvalues.put("String1", propValue1);
        Propvalues.put("String2", propValue2);

        book2 book1 = new book2("id1", "title1", "content1", Propvalues);
        book2 book2;

        try{
            entityTransaction.begin();
            entityManager.persist(book1);
            entityTransaction.commit();
        }catch (NullPointerException exception){
            throw new NullPointerException();
        }

        try{
            book2 = entityManager.find(book2.class, "id1");
            System.out.println(book2);
        }catch(NullPointerException exception){
            throw new NullPointerException();
        }finally {
            entityManager.close();
        }

        entityManagerFactory.close();

    }
}

이렇게 동작하는 것을 볼 수 있다.