Question

假设我们有3个实体

<class name="AEntity" table="A" abstract="true">
    <id name="id">
        <column name="ID"/>
    </id>

    <joined-subclass table="Aa" name="AaEntity">
        <key column="key"/>
        <many-to-one name="b" class="BEntity">
            <column name="B_ID"/>
        </many-to-one>
    </joined-subclass>

    <joined-subclass table="Ab" name="AbEntity">
        <key column="key"/>
        <many-to-one name="b" class="BEntity">
            <column name="B_ID"/>
        </many-to-one>
    </joined-subclass>
</class>

<hibernate-mapping>
    <class name="Parent" table="parent">
        <id name="id">
            <column name="ID"/>
        </id>
        <many-to-one name="a" class="AEntity">
            <column name="a_ID" />
        </many-to-one>
    </class>
</hibernate-mapping>

<hibernate-mapping>
    <class name="BEntity" table="B">
        <id name="id">
            <column name="ID"/>
        </id>
    </class>
</hibernate-mapping>

然后，我们制定标准请求

Criteria criteria = session.createCriteria(Parent.class);
criteria.createAlias("a","a");
criteria.createAlias("a.b","b");
criteria.list();

然后获取下一个sql

select this_.ID as ID1_5_3_,
       this_.a_ID as a2_5_3_,
       a1_.ID as ID1_2_0_,
       a1_.B_ID as B2_2_0_,
       a1_1_.B_ID as B2_0_0_,
       a1_2_.B_ID as B2_1_0_,
       case when a1_1_.key is not null then 1 when a1_2_.key is not null then 2 when a1_.ID is not null then 0 end as clazz_0_,
       b2_.ID as ID1_3_1_,
       b2_.C_ID as C2_3_1_,
       b2_.ID as ID1_3_2_,
       b2_.C_ID as C2_3_2_
from parent this_
inner join A a1_ on this_.a_ID=a1_.ID
left outer join Aa a1_1_ on a1_.ID=a1_1_.key
left outer join Ab a1_2_ on a1_.ID=a1_2_.key
inner join B b2_ on a1_1_.B_ID=b2_.ID
inner join B b2_ on a1_2_.B_ID=b2_.ID

我们可以看到B表连接两次并且具有相同的名称b2_。是bug吗？如何使两个连接但具有不同的B表名称。好吗？

Answer 1

尝试像

这样的别名

Criteria criteria = session.createCriteria(Parent.class, "parent");
criteria.createAlias("parent.a","a");
criteria.createAlias("parent.a.AaEntity.b","aab");
criteria.createAlias("parent.a.AbEntity.b","abb");
criteria.list();

PS：我没有对此进行测试，它可能无法正常工作，但这会让您了解如何强制使用别名。

Hibernate为不同的连接创建相同的别名

1 个答案: