Hibernate 如何区分加入的子类

Question

假设我有以下实体模型案例并使用 Hibernate 3.6:

Person
    |__ Student
            |__ SchoolBoy
            |__ CollegeStudent

我在数据库中的表是 tperson 和 学生 .当我使用 hibernate 映射文件时，我将其如下声明到我的 Person 实体定义中:

<joined-subclass name="Student" table="tstudent">
    <key column="id_person" />
</joined-subclass>

作为类似于 CollegeStudent 的 SchoolBoy，我想为两个 (tstudent) 使用同一张 table ，有一个 学生型鉴别器列，而我保留了两个类。我的问题是，一旦您进入连接子类，Hibernate 似乎不允许使用鉴别器列。

有解决方法吗？

更新

这就是我现在所拥有的:

<class name="Person">
    <id name="Id" column="id" type="integer">
        <generator class="increment" />
    </id>
    <joined-subclass name="Student" table="tstudent">
        <key column="id_person" />
        <joined-subclass name="SchoolBoy" table="tschoolboy">
            <key column="id_person" />
        </joined-subclass>
        <joined-subclass name="CollegeStudent" table="tcollegestudent">
            <key column="id_person" />
        </joined-subclass>
    </joined-subclass>
</class>

这就是我希望在映射的 join 部分拥有的内容:

<joined-subclass name="Student" table="tstudent">
    <key column="id_person" />
    <discriminator column="student_type" />
    <subclass name="SchoolBoy" discriminator-value="SCHOOL_BOY" />
    <subclass name="CollegeStudent" discriminator-value="COLLEGE_STUDENT" />
</joined-subclass>

Answer 1

hibernate 文档说:

Hibernate does not support mixing <subclass>, <joined-subclass> and <union-subclass> mappings under the same root <class> element. It is possible to mix together the table per hierarchy and table per subclass strategies under the the same <class> element, by combining the <subclass> and <join> elements

在您的情况下，您需要将鉴别器列移动到 tperson table 并使用 join 元素为您的学生类添加额外的属性。

<class name="Person" table="tperson" discriminator-value="PERSON">
    <id name="Id" column="id" type="integer">
        <generator class="increment" />
    </id>
    <discriminator column="person_type" />
    <subclass name="Student" discriminator-value="STUDENT">
        <key column="id_person" />
        <subclass name="SchoolBoy" discriminator-value="SCHOOL_BOY">
            <join table="tstudent">
                <key column="id_person" />
                ...
            </join>
        </subclass>
        <subclass name="CollegeStudent" discriminator-value="COLLEGE_STUDENT">
            <join table="tstudent">
                <key column="id_person" />
                ...
            </join>
        </subclass>
    </subclass>
</class>

您也可以在 Student 子类元素中为所有学生共有的属性添加一个连接