Hibernate：类继承的实现方式（二）--父子类各自一个表

将继承链中的各个类映射到数据库中的一个单独的表中

domain对象和测试代码同（一）


可以看到在关系模型中比较合理：Employee表中没有空字段，但是查询效率肯定会受影响

映射文件如下：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="cn.itcast.hibernate.inherit2">

	<class name="Employee" table="employee" >
		<id name="id" unsaved-value="-1">
			<generator class="native" />
		</id>
		<property name="name"/>

		<joined-subclass name="Skiller" table="skiller">
			<key column="s_id"/>
			<property name="skill"/>
		</joined-subclass>
		
		<joined-subclass name="Driver" table="dirver">
			<key column="d_id"/>
			<property name="driverYears"/>
		</joined-subclass>
		
	</class>
</hibernate-mapping>

执行的sql语句如下：

Hibernate: insert into employee (name) values (?)
Hibernate: insert into employee (name) values (?)
Hibernate: insert into skiller (skill, s_id) values (?, ?)
Hibernate: insert into employee (name) values (?)
Hibernate: insert into dirver (driverYears, d_id) values (?, ?)

评论

1 楼 Rod_johnson 2011-09-15  

学习了！真不错