Hibernate/JPA 单表一对多关系映射

这里以组织机构为例：

表结构

字段	类型	备注
OrgId	NUMBER(10)	主键
OrgName	Varchar2(128)	组织机构名称
ParentId	NUMBER(10)	父机构ID，外键参考OrgId

实体类：Org

import org.hibernate.Session;
import org.junit.Before;
import org.junit.Test;
import commons.utils.HibernateUtil;

public class TestOrg {
@Before
private void test1() {
Session session = HibernateUtil.getCurrentSession();
session.getTransaction().begin();

Org o, o1, o2, o11, o12;
o = new Org("org");
o.setParentId((Org) session.get(Org.class, new Long(-100)));
o1 = new Org("-org1");
o2 = new Org("-org2");
o11 = new Org("--org11");
o12 = new Org("--org12");
o11.setParentId(o1);
o12.setParentId(o1);
o1.setParentId(o);
o2.setParentId(o);
session.save(o);
session.save(o1);
session.save(o2);
session.save(o11);
session.save(o12);
session.getTransaction().commit();
session.close();
}

@Test
private void test2() {
Session session = HibernateUtil.getCurrentSession();
session.getTransaction().begin();
Org o = (Org) session.createQuery("from Org o where o.parentId is null").uniqueResult();
System.out.println(o.getOrgName() + "-" + o.getOrgId());
Org o1 = new Org("-org3");
o1.setParentId(o);
session.save(o1);
session.getTransaction().commit();
session.close();
}
}