hibernate继承关系映射方法（三）--每个具体类一张表TPC

TPC:所谓是“每个具体类一张表(table per concrete class)”的意思是:使继承体系中每一个子类都对应数据库中的一张表。每一个子类对应的数据库表都包含了父类的信息，并且包含了自己独有的属性。每个子类对应一张表，而且这个表的信息是完备的，即包含了所有从父类继承下来的属性映射的字段。这种策略是使用<union-subclass>标签来定义子类的。





注意：三个类+一个父类映射文件+两张表



student表



worker表



测试工程：



Person.java

package com.hust.PO;

public class Person {
private Integer id;
private String name; //姓名
private Integer age; //年龄
private String sex; //性别
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}

}
Student.java
package com.hust.PO;

public class Student extends Person {

private String sno; //学号
private String school; //学校

public String getSno() {
return sno;
}
public void setSno(String sno) {
this.sno = sno;
}
public String getSchool() {
return school;
}
public void setSchool(String school) {
this.school = school;
}

}
Worker.java
package com.hust.PO;

public class Worker extends Person {

private String wno; //工号
private Double salary; //工资

public String getWno() {
return wno;
}
public void setWno(String wno) {
this.wno = wno;
}
public Double getSalary() {
return salary;
}
public void setSalary(Double salary) {
this.salary = salary;
}

}
父类映射文件Person.hbm.xml
<?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="com.hust.PO">
<!-- table per concrete(TPC) (a. 具体的，实际的) -->
<!-- 每一个具体类一张表 -->
<!-- 虚拟选项为'true' -->
<class name="Person" table="person" abstract="true"> <!-- 多设置一个属性abstract="true"，因为根本就没有person表 -->
<id column="Id" name="id" type="integer">
<!-- 主键的生成策略为'分配' -->
<generator class="assigned"></generator>
</id>
<property column="Name" name="name" type="string"></property>
<property column="Sex" name="sex" type="string"></property>
<property column="Age" name="age" type="integer"></property> <!-- 公共属性 -->

<!--student具体类-->
<union-subclass name="Student" table="student">
<property column="Sno" name="sno" type="string"></property> <!-- 特征属性 -->
<property column="School" name="school" type="string"></property> <!-- 特征属性 -->
</union-subclass>

<!--worker具体类-->
<union-subclass name="Worker" table="worker">
<property column="Wno" name="wno" type="string"></property> <!-- 特征属性 -->
<property column="Salary" name="salary" type="double"></property> <!-- 特征属性 -->
</union-subclass>

</class>
</hibernate-mapping> <union-subclass>标签是用于指示出该hbm文件所表示的类的子类，如Person类有两个子 类，就需要两个<union-subclass>标签以此类推。
<union-subclass>标签的"name"属性用于指 定子类的全限定名称，"table"属性用于指定该子类对应的表的名称，"extends"属性用于指定该子类的父类，

注意:"extends"属性与<union-subclass>标签的位置有关，若<union-subclass>标签作为<class>标签的子标签，则"extends"属性可以不设置，否则需要明确设置"extends"属性。

<class>标签中的"abstract"属性如果值为true则，不会生成表结构。如果值为false则会生成表结构，但是不会插入数据。

数据库文件TableDao.java

package com.hust.Dao;

import org.hibernate.Session;
import org.hibernate.Transaction;
import SessionFactory.HibernateSessionFactory;
import com.hust.PO.Student;
import com.hust.PO.Worker;

public class TableDao {
//保存学生信息
public void saveStu(Student stu){
Session session=HibernateSessionFactory.getSession();
Transaction ts=null;
try{
ts=session.beginTransaction();
session.saveOrUpdate(stu);
ts.commit();
}catch(Exception ex){
ts.rollback();
System.out.println("添加学生信息失败");
}finally{
HibernateSessionFactory.closeSession();
}
}
/*session.saveOrUpdate(stu);控制台打印的HQL
* Hibernate:
select
student_.Id,
student_.Name as Name0_,
student_.Sex as Sex0_,
student_.Age as Age0_,
student_.Sno as Sno1_,
student_.School as School1_
from
student student_
where
student_.Id=?
Hibernate:
insert
into
student
(Name, Sex, Age, Sno, School, Id)
values
(?, ?, ?, ?, ?, ?)
*/
//加载学生信息
public Student loadStu(Integer id){
Session session=HibernateSessionFactory.getSession();
Transaction ts=null;
Student stu=null;
try{
ts=session.beginTransaction();
stu=(Student)session.get(Student.class, id);
ts.commit();
}catch(Exception ex){
ts.rollback();
System.out.println("加载学生信息失败");
}finally{
HibernateSessionFactory.closeSession();
}
return stu;
}
/* stu=(Student)session.get(Student.class, id);控制台打印的HQL
Hibernate:
select
student0_.Id as Id0_0_,
student0_.Name as Name0_0_,
student0_.Sex as Sex0_0_,
student0_.Age as Age0_0_,
student0_.Sno as Sno1_0_,
student0_.School as School1_0_
from
student student0_
where
student0_.Id=?*/
//保存工人信息
public void saveWorker(Worker worker){
Session session=HibernateSessionFactory.getSession();
Transaction ts=null;
try{
ts=session.beginTransaction();
session.saveOrUpdate(worker);
ts.commit();
}catch(Exception ex){
ts.rollback();
System.out.println("添加工人信息失败");
}finally{
HibernateSessionFactory.closeSession();
}
}
/*session.saveOrUpdate(worker);控制台打印的HQL
* Hibernate:
select
worker_.Id,
worker_.Name as Name0_,
worker_.Sex as Sex0_,
worker_.Age as Age0_,
worker_.Wno as Wno2_,
worker_.Salary as Salary2_
from
worker worker_
where
worker_.Id=?
Hibernate:
insert
into
worker
(Name, Sex, Age, Wno, Salary, Id)
values
(?, ?, ?, ?, ?, ?)
*/
//加载工人信息
public Worker loadWorker(Integer id){
Session session=HibernateSessionFactory.getSession();
Transaction ts=null;
Worker worker=null;
try{
ts=session.beginTransaction();
worker=(Worker)session.get(Worker.class, id);
ts.commit();
}catch(Exception ex){
ts.rollback();
System.out.println("加载工人信息失败");
}finally{
HibernateSessionFactory.closeSession();
}
return worker;
}
/*worker=(Worker)session.get(Worker.class, id);控制台打印的HQL
*
* Hibernate:
select
worker0_.Id as Id0_0_,
worker0_.Name as Name0_0_,
worker0_.Sex as Sex0_0_,
worker0_.Age as Age0_0_,
worker0_.Wno as Wno2_0_,
worker0_.Salary as Salary2_0_
from
worker worker0_
where
worker0_.Id=?

*/

}
测试页面test.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page import="com.hust.Dao.*" %>
<%@ page import="com.hust.PO.*" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>hibernate的继承关系（三）每个具体类一张表TPC</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<h2>hibernate的继承关系（三）--每个具体类一张表TPC</h2>
<hr>
<%
//新建学生对象
Student stu=new Student();
stu.setId(new Integer(1));
stu.setName("tuke");
stu.setAge(new Integer(22));
stu.setSex("nan");
stu.setSno("M201571885");
stu.setSchool("华中科技大学");
//保存stu对象
TableDao dao=new TableDao();
dao.saveStu(stu);
//从数据库中获取stu对象
Student stu1=dao.loadStu(stu.getId()); //加载子类对象

out.println("<br>数据库中的学生姓名："+stu1.getName()); //共有属性
out.println("<br>数据库中的学生学号："+stu1.getSno()); //特征属性
out.println("<br>数据库中的学生学校："+stu1.getSchool()); //特征属性
out.println("<br>");

//新建工人对象
Worker worker=new Worker();
worker.setId(new Integer(2));
worker.setName("李四");
worker.setAge(new Integer(34));
worker.setSex("nan");
worker.setWno("W20152223");
worker.setSalary(new Double(5435.32));
//保存工人对象
dao.saveWorker(worker);
//从数据库中获取工人对象
Worker worker2=dao.loadWorker(worker.getId()); //加载子类对象的时候，会使用内连接语句inner join、

out.println("<br>数据库中的工人姓名："+worker2.getName()); //共有属性
out.println("<br>数据库中的工人工号："+worker2.getWno()); //特征属性
out.println("<br>数据库中的工人工资："+worker2.getSalary());//特征属性
%>
</body>
</html>
测试结果：



student表插入的值：



worker表插入的值：



控制台打印店的HQL
Hibernate:
select
student_.Id,
student_.Name as Name0_,
student_.Sex as Sex0_,
student_.Age as Age0_,
student_.Sno as Sno1_,
student_.School as School1_
from
student student_
where
student_.Id=?
Hibernate:
insert
into
student
(Name, Sex, Age, Sno, School, Id)
values
(?, ?, ?, ?, ?, ?)
Hibernate:
select
student0_.Id as Id0_0_,
student0_.Name as Name0_0_,
student0_.Sex as Sex0_0_,
student0_.Age as Age0_0_,
student0_.Sno as Sno1_0_,
student0_.School as School1_0_
from
student student0_
where
student0_.Id=?
Hibernate:
select
worker_.Id,
worker_.Name as Name0_,
worker_.Sex as Sex0_,
worker_.Age as Age0_,
worker_.Wno as Wno2_,
worker_.Salary as Salary2_
from
worker worker_
where
worker_.Id=?
Hibernate:
insert
into
worker
(Name, Sex, Age, Wno, Salary, Id)
values
(?, ?, ?, ?, ?, ?)
Hibernate:
select
worker0_.Id as Id0_0_,
worker0_.Name as Name0_0_,
worker0_.Sex as Sex0_0_,
worker0_.Age as Age0_0_,
worker0_.Wno as Wno2_0_,
worker0_.Salary as Salary2_0_
from
worker worker0_
where
worker0_.Id=?