Hibernate映射关系配置（五）

多表继承：

Bean：

public class Person implements Serializable{

    private int id ;

    private String name ;

    private int age ;
}
public class Student extends Person implements Serializable {

    private String dream ;

    private Date birthday ;
}
public class Teacher extends Person implements Serializable{

    private String job ;

    private boolean merry ;
}

xml（在同一个表中，加一个字段来区分类型）：

Person.hbm.xml：
<class name = "Person" discriminator-value="p">
        <id name = "id">
            <generator class="native" />
        </id>
        <!-- discriminator 是新建一个列,此列用来区分对象具体的类型
             discriminator-value 定义插入一个具体的对象的时候,自动向type列中插入指定的值
        -->
        <discriminator column="type" />
        <property name="name" />
        <property name="age" />

        <subclass name = "Teacher" discriminator-value="t">
             <property name="job" />
             <property name="merry" />
        </subclass>

        <subclass name = "Student" discriminator-value="s">
             <property name="dream" />
             <property name="birthday" />
        </subclass>
    </class>
    

xml（在不同表中）：

Person.hbm.xml:
<class name = "Person">
        <id name = "id">
            <generator class="native" />
        </id>

        <property name="name" />
        <property name="age" />

        <joined-subclass name="Teacher" table="Teacher">
            <key column="pid" />
            <property name="job" />
            <property name="merry" />
        </joined-subclass>

        <joined-subclass name="Student" table="Student">
            <key column="pid" />
            <property name="dream" />
            <property name="birthday" />
        </joined-subclass>

    </class>