[JPA_Basic] 페이징

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

 

👉 기본 환경

- Language: Java

- DB: H2 Database

- IDE: IntelliJ

 

 

페이징

⌨️ 코드

public class Main {
    public static void main(String[] args) {
 
        EntityManagerFactory emf = Persistence.createEntityManagerFactory("hello");
 
        EntityManager em = emf.createEntityManager();
 
        EntityTransaction tx = em.getTransaction();
        tx.begin(); // transaction 시작 선언
 
        try {
 
            for(int i=0; i<100; i++){
                Member member = new Member();
                member.setName("Member" + (i+1));
                member.setAge(i+1);
                em.persist(member);
 
            }
 
            em.flush();
            em.clear();
 
            List<Member> members = em.createQuery("select m from Member m order by m.age desc", Member.class)
                    .setFirstResult(11)
                    .setMaxResults(10)
                    .getResultList();
 
            System.out.println("members.size: " + members.size());
 
            for(Member m : members)
                System.out.println("member: " + m);
 
            tx.commit(); // transaction 종료 후 commit
        } catch (Exception e) {
            tx.rollback(); // 문제가 생길 경우, rollback 진행
            e.printStackTrace();
        } finally {
            em.close(); // tx에 문제가 생기더라도 em 반드시 종료
        }
            emf.close();
    }
}
 

- setFirstResult(): 첫번째 레코드

- setMaxResults(): 페이지 당 레코드 수

 

🖨️발생한 쿼리

Hibernate: 
    /* select
        m 
    from
        Member m 
    order by
        m.age desc */ select
            member0_.id as id1_0_,
            member0_.age as age2_0_,
            member0_.name as name3_0_,
            member0_.TEAM_ID as team_id4_0_ 
        from
            Member member0_ 
        order by
            member0_.age desc limit ? offset ?