[자바 ORM 표준 JPA 프로그래밍] [섹션 0~2] JPA 시작하기

pom.xml 설정

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>jpa-basic</groupId>
    <artifactId>ex1-hello-jpa</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- JPA 하이버네이트 -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.3.10.Final</version>
        </dependency>

        <!-- H2 DB -->
        <!-- 버전을 꼭 다운로드 받았을 때의 버전과 맞춰줘야함 -->
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>2.2.220</version>
        </dependency>
    </dependencies>
</project>

 

persistence.xml 설정

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.2"
             xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_2.xsd">
    <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-->
            <!-- show_sql은 쿼리가 나가는걸 보여주는 옵션설정
                 foramt_sql은 이쁘게 포맷팅
                 use_sql_comments는 이쿼리가 나온 이유에 대한 코멘트
            -->
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>
            <property name="hibernate.use_sql_comments" value="true"/>
            <!--<property name="hibernate.hbm2ddl.auto" value="create" />-->
        </properties>
    </persistence-unit>
</persistence>

 

데이터베이스 방언

• persistence.xml의 <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" /> 를 수정

 

 

DB

create table Member (
    id bigint not null,
    name varchar(255),
    primary key (id)
);

 

JpaMain.java

package hellojpa;

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) {
        // Persistence.xml에서 설정해준 name으로 factory를 만들어서 연결
        // 웹 서버가 올라오는 시점에 딱 1개만 생성
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");

        // 고객의 요청이 올 때마다 썼다가 버림(em.close)
        // 그래서 쓰레드간에 절대 공유 X(사용하고 버려야됨)
        EntityManager em = emf.createEntityManager();

        EntityTransaction tx = em.getTransaction();

        tx.begin();

        // JPA의 모든 DATA 변경은 트랜잭션 안에서 실행
        // 단순 조회는 트랜잭션 필요 X
        try {
            // * insert
//            Member member = new Member();
//            member.setId(1L);
//            member.setName("HelloA");
//            em.persist(member);

            // * select
//            Member findMember = em.find(Member.class, 1L);
//            System.out.println("findMember.id = " + findMember.getId());
//            System.out.println("findMember.name = " + findMember.getId());

            // * delete
//            Member findMember = em.find(Member.class, 1L);
//            em.remove(findMember);

            // * update
            // 객체에서 값만 바꿔도 되는 이유는 JPA가 관리해서 트랜잭션을
            // 커밋하는 시점에 다 체크해서 UPDATE 쿼리를 만들어서 날림 그 이후에 커밋
            Member findMember = em.find(Member.class, 1L);
            findMember.setName("HelloJPA");

            tx.commit();
        } catch (Exception e) {
            tx.rollback();
        } finally {
            em.close();
        }

        emf.close();
    }
}

 

Member.java

package hellojpa;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Member {
    @Id
    private Long id;
    private String name;

    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;
    }
}

 

 

JPQL