hibernate的三表查询

表的关系:

Cardgraderule      1:n     Cardgrade

Cardgrade           1:n     Acardtype

实体类:

public class Cardgraderule implements java.io.Serializable {

    private Cardgrade cardgrade;
        ......
}

public class Cardgrade implements java.io.Serializable {

    private Acardtype cardtype;
        ......

1.通过Criteria查询实现三表查询

封装的dao方法:

public class BaseDAOHibernate extends HibernateDaoSupport{

    public List findAllByCriteria(final DetachedCriteria detachedCriteria)  throws DataAccessException  {
                return (List)getHibernateTemplate().execute(new HibernateCallback() { 

                    public Object doInHibernate(Session session)  throws HibernateException  {
                        Criteria criteria = detachedCriteria.getExecutableCriteria(session);
                        return criteria.list();
                    }
                }
        , true);
     }
}  

业务方法:

//createAlias()

 DetachedCriteria cardy2 = DetachedCriteria.forClass(Cardgraderule.class, "cardgraderule");
     cardy2.createAlias("cardgrade","g")
     　　　 .add(Restrictions.eq("g.cardtype.agentid", agenttbl.getAgentid()));
     List list = commonDao.findAllByCriteria(cardy2);

下图是listCardgrade的封装规格:  可以看到返回的是  Cardgraderule

2.通过hql实现三表查询

封装的dao方法:

public class BaseDAOHibernate extends HibernateDaoSupport{

     public List find(String query)  throws DataAccessException {

         return getHibernateTemplate().find(query);
    }
}    

业务方法:

第一种写法:

//    1.cardgrade是Cardgraderule的属性//    2.select 后 跟的是实体的别名

 String hql = "select distinct c from Cardgraderule c left join fetch c.cardgrade  g  left join fetch g.cardtype";
 List find = commonDao.find(hql);

第二种写法:

select ck  from  Cardgraderule a,Cardgrade ck  where a.cardtype = ck.cardtype.cardtype

结果的封装: