hibernate详解(七)---映射继承关系

来源：互联网发布：floyd算法的流程图编辑：程序博客网时间：2024/06/10 22:46

Hibernate支持三种继承映射策略

一.采用 subclass 元素的继承映射

备注:school就是下面的sname

1.建立Person类

package com.eduask.chp.joinsubclass;public class Person {private  int id;private String name;private int age;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}

2.子类Student类

public class Student extends Person{private String sname;//学校名称public String getSname() {return sname;}public void setSname(String sname) {this.sname = sname;}}

3.Person.hbm.xml

<hibernate-mapping package="com.eduask.chp.subclass">    <class name="Person" table="PERSONS" discriminator-value="person1">        <id name="id" type="int">            <column name="ID" />            <generator class="native" />        </id>        <!-- 辨别者列 -->      <discriminator type="string" column="type"></discriminator>        <property name="name" type="java.lang.String">            <column name="NAME" />        </property>        <property name="age" type="int">            <column name="AGE" />        </property>        <!-- 映射子类Student,使用subclass -->        <subclass name="Student" discriminator-value="student1">        <property name="sname" type="string" column="SNAME"></property>        </subclass>    </class></hibernate-mapping>

二.采用 joined-subclass 元素的继承映射

修改Person.hbm.xml文件

<hibernate-mapping package="com.eduask.chp.subclass">    <class name="Person" table="PERSONS">        <id name="id" type="int">            <column name="ID" />            <generator class="native" />        </id>        <property name="name" type="java.lang.String">            <column name="NAME" />        </property>        <property name="age" type="int">            <column name="AGE" />        </property>        <joined-subclass name="Student" table="STUDENTS">        <key column="student_id"></key>        <property name="sname" type="string" column="SNAME"></property>        </joined-subclass>    </class></hibernate-mapping>

三.采用 union-subclass 元素的继承映射

Person.hbm.xml

<hibernate-mapping package="com.eduask.chp.union.subclass">    <class name="Person" table="PERSONS">        <id name="id" type="int">            <column name="ID" />            <generator class="hilo" />        </id>           <property name="name" type="java.lang.String">            <column name="NAME" />        </property>        <property name="age" type="int">            <column name="AGE" />        </property>        <union-subclass name="Student" table="STUDENTS">        <property name="sname" type="string" column="SNAME"></property>        </union-subclass>    </class></hibernate-mapping>

三者的区别:

阅读全文

0 0