hibernate：继承关系_整个继承树映射到一张表

domain类：
Employee.java

package com.zhaosoft.domain;

public class Employee {

?private int id;
?private String name;
?private Department depart;

?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 Department getDepart() {
??return depart;
?}

?public void setDepart(Department depart) {
??this.depart = depart;
?}

}

两个子类：
sales.java

package com.zhaosoft.domain;

public class Sales extends Employee{

?private int sell;//销售额

?public int getSell() {
??return sell;
?}

?public void setSell(int sell) {
??this.sell = sell;
?}
}
Skiller.java

package com.zhaosoft.domain;

public class Skiller extends Employee{
?private String skill;

?public String getSkill() {
??return skill;
?}

?public void setSkill(String skill) {
??this.skill = skill;
?}
?

}

映射文件：
<?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.zhaosoft.domain">
???? <!-- 当discriminator-value值为0时，为普通员工 -->
?<class name="Employee" discriminator-value="0">??
??<id name="id">
????? <!-- 表示主键为自动增长 -->
???<generator type="int"/>
?<property name="name" type="string"/>
?<many-to-one name="depart" column="depart_id"></many-to-one>
?<!-- 当为1时，为技术人员 -->
?<subclass name="Skiller" discriminator-value="1">
??? <property name="skill"></property>
?</subclass>
?<!-- 当为2时为销售人员 -->
?<subclass name="Sales" discriminator-value="2">
?? <property name="sell"></property>
?</subclass>
?</class>
</hibernate-mapping>
测试：

package com.zhaosoft.test;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.zhaosoft.domain.Department;
import com.zhaosoft.domain.Employee;
import com.zhaosoft.domain.Sales;
import com.zhaosoft.domain.Skiller;
import com.zhaosoft.hibernate.HibernateUtil;

public class Many2One {
?public static void main(String[] args) {
??add();
??//queryDepartment(1);
??//queryEmployee(1);
?}

?public static void queryDepartment(int id) {
??Session s = HibernateUtil.getSession();
??try {
???Transaction t = s.beginTransaction();
???t.begin();
???Department de = (Department) s.get(Department.class, 1);
???
???t.commit();
???Hibernate.initialize(de.getEmps());
???System.out.println(de.getName());
???Set<Employee> set=de.getEmps();?? //加载数据
???Iterator<Employee> it=set.iterator();
???while(it.hasNext()){
???Employee employee=?it.next();
???System.out.println(employee.getName());
???}
???
??} catch (Exception e) {

??} finally {
???if (s != null) {
????s.close();
???}
??}

?}

?public static Employee queryEmployee(int id) {

??Session s = null;
??Transaction tx=null;
??try {

???s=HibernateUtil.getSession();
???tx=s.beginTransaction();
???Employee emp=(Employee)s.get(Employee.class,id);
???//Hibernate.initialize(emp.getDepart());
???tx.commit();
???return emp;
??} finally {
???if (s != null) {
????s.close();
???}
??}

?}

?public static void add() {
??Session s = null;
??Transaction t=null;
??try {
???s=HibernateUtil.getSession();
???t = s.beginTransaction();
???t.begin();
???Department d = new Department();
???d.setName("销售部");

???Employee employee1 = new Employee();
???employee1.setName("小三");
???employee1.setDepart(d);

???Skiller employee2 = new Skiller();
???employee2.setName("李斯");
???employee2.setSkill("skill");
???employee2.setDepart(d);
???
???Sales employee3 = new Sales();
???employee3.setName("王五");
???employee3.setSell(100);
???employee3.setDepart(d);

???Set<Employee> set=new HashSet<Employee>();
???set.add(employee1);
???set.add(employee2);
???set.add(employee3);
???d.setEmps(set);
???s.save(d);
???s.save(employee1);
???s.save(employee2);
???s.save(employee3);
???
???t.commit();
??} catch (Exception e) {

??} finally {
???if (s != null) {
????s.close();
???}
??}
?}
}