[springboot] JPA - 1. JPA 소개 및 시작

spring: datasource: driver-class-name: com.mysql.cj.jdbc.Driver url: jdbc:mysql://localhost:3306/hello-jpa?serverTimezone=Asia/Seoul username: root password: <password> jpa: show-sql: true hibernate: ddl-auto: none

<?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"> <class>jpabasic.hellojpa.Member</class> <properties> <!-- 필수 속성 --> <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/> <property name="javax.persistence.jdbc.user" value="root"/> <property name="javax.persistence.jdbc.password" value="<password>"/> <property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/hello-jpa?serverTimezone=Asia/Seoul"/> <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect"/> <!-- 옵션 --> <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>

@SpringBootApplication public class HelloJpaApplication { public static void main(String[] args) { SpringApplication.run(HelloJpaApplication.class, args); EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello"); EntityManager em = emf.createEntityManager(); // em : DB connection EntityTransaction tx = em.getTransaction(); tx.begin(); // 트랜잭션 시작 try { Member member = new Member(); member.setId(1L); member.setName("HelloA"); // INSERT em.persist(member); // SELECT Member findMember = em.find(Member.class, 1L); // findMember : JPA 를 통해서 가져온 객체는 DB와 연결돼있다고 보면 됨 System.out.println("findMember.id = " + findMember.getId()); System.out.println("findMember.name = " + findMember.getName()); // JPQL 을 이용한 여러 개 SELECT List<Member> result = em.createQuery("select m from Member as m", Member.class) .setFirstResult(5) .setMaxResults(8) .getResultList(); for (Member mem : result) { System.out.println("member name = " + mem.getName()); } // UPDATE findMember.setName("HelloB"); // 자바 객체 멤버를 바꾸는 것처럼 보이지만 DB에도 반영이 됨 // DELETE //em.remove(findMember); tx.commit(); // 트랜잭션 커밋 } catch (Exception e) { tx.rollback(); // 트랜잭션 롤 } finally { em.close(); } emf.close(); } }