JPA FetchType에 따른 쿼리 생성

 private static void readRole(String roleId) {
        logger.info("readRole");
        EntityManager em = EMF.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        try {
            tx.begin();
            Role role = em.find(Role.class, roleId);
            logger.info("role id: {}", role.getId());
            for (String perm : role.getPermissions()) {
                logger.info("perm: {}", perm);
            }
            tx.commit();
        } catch (Exception ex) {
            tx.rollback();
            throw ex;
        } finally {
            em.close();
        }
    }

• FetchType.EAGER -> 한방쿼리 -> 객체에서 getPermission()해도 아무일도 안일어남

  select r1_0.id,r1_0.name,p1_0.role_id,p1_0.perm from role r1_0 left join role_perm p1_0 on r1_0.id=p1_0.role_id where r1_0.id=?

• FetchType.LAZY -> 나눠서 쿼리 -> 객체.getPermission() 하면 쿼리 호출 와우

  select r1_0.id,r1_0.name from role r1_0 where r1_0.id=?
  select p1_0.role_id,p1_0.perm from role_perm p1_0 where p1_0.role_id=?