IT 유목민의 삶

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
 <persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence" version="2.2"
              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence">

    <persistence-unit name="hello">
        <properties>
            <!-- 필수 속성 -->
            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
            <property name="javax.persistence.jdbc.user" value="sa"/>
            <property name="javax.persistence.jdbc.password" value=""/>
            <property name="javax.persistence.jdbc.url" value="jdbc:h2:tcp://localhost/~/test"/>
            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
            <!-- 옵션  -->
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.use_sql_comment" value="false"/>
            <property name="hibernate.id.new_generator_mappings" value="true" />
            <property name="hibernate.jdbc.batch_size" value="10"/>
            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
            <property name="connection.autocommit" value="false"/>
        </properties>
    </persistence-unit>
</persistence>

Member.java

import javax.persistence.*;

@Entity

public class Member {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "MEMBER_ID")
    private Long id;

    @Column(name = "MEMBER_NAME", nullable = false)
    private String name;

    public Member() {}

    public Long getId(){
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Member(Long id, String name){
        this.id = id;
        this.name = name;
    }
}

JpaMain.java

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

public class JpaMain {
    public static void main(String[] args ) {
        System.out.println("시작 ------");
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
        EntityManager em  = emf.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        tx.begin();

        try {
            //비영속 상태
            Member member = new Member();
            member.setId(1L);   <------ 문제의 코드
            member.setName("test");
            System.out.println("=== 이전 =====");

            //entity를 영속 (1차캐시에 저장한다)
            em.persist(member);
            System.out.println("=== 이후 =====");

            tx.commit();
        }catch(Exception e){
            System.out.println("롤백이 진행됨");
            System.out.println(e.getMessage());
            e.printStackTrace();
            tx.rollback();
        }finally {
            em.close();
        }

    }
}

@GeneratedValue(strategy = GenerationType.IDENTITY) 전략에 대해 검색해봄

기본키 생성을 데이터베이스에 위임한다. 

id 값을 null로 하면 DB가 알아서 AUTO_INCREMENT 해준다
https://gmlwjd9405.github.io/2019/08/12/primary-key-mapping.html

위 글을 보니 문제가 어디인지 감이 잡힘. 

데이터베이스에 id값을 생성하라고 위임을 해놓고 임의로 셋팅하려고 하니 문제가 발생된것으로 보임. 

member.setId(1L);   <------ 문제의 코드

[에러코드]

javax.persistence.PersistenceException: org.hibernate.PersistentObjectException: detached entity passed to persist: Member
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)
	at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:762)
	at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:742)
	at JpaMain.main(JpaMain.java:22)

member.setId(1L); 이부분을 주석처리하면 아래와 같이 정상 동작함. 

=== 이전 =====
Hibernate: 
    insert 
    into
        Member
        (MEMBER_ID, MEMBER_NAME) 
    values
        (default, ?)
=== 이후 =====
====================