Hibernate中类的继承使用union-subclass实现

package blog.hibernate.domain;

public class Employee {
private int id;
private String name;

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;
}

@Override
public String toString() {
return "Employee{" + "id=" + id + ", name=" + name + '}';
}
}

package blog.hibernate.domain;

public class Sale extends Employee {
private int sell;

public int getSell() {
return sell;
}

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

@Override
public String toString() {
return "Sale{"  + "id=" + this.getId() + ", name=" + this.getName() + "sell=" + sell + '}';
}
}

package blog.hibernate.domain;

public class Skill extends Employee{
private String skiller;

public String getSkiller() {
return skiller;
}

public void setSkiller(String skiller) {
this.skiller = skiller;
}

@Override
public String toString() {
return "Skill{"  + "id=" + this.getId() + ", name=" + this.getName() + "skiller=" + skiller + '}';
}
}

<?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="blog.hibernate.domain">
<class name="Employee" table="employees">
<id name="id" column="EMPLOYEE_ID">
<generator class="hilo" />
</id>
<property name="name" column="EMPLOYEE_NAME" />

<union-subclass name="Sale" table="SALE">
<property name="sell" column="SELL"/>
</union-subclass>

<union-subclass name="Skill" table="SKILL">
<property name="skiller" column="SKILLER"/>
</union-subclass>
</class>
</hibernate-mapping>

package blog.hibernate;

import java.util.logging.Level;
import java.util.logging.Logger;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public final class HibernateUtil {

private static SessionFactory sessionFactory;
private HibernateUtil(){}

static{
Configuration cfg = new Configuration();
sessionFactory =  cfg.configure("hibernate.cfg.xml").buildSessionFactory();
}

public static SessionFactory getSessionFactory(){
return sessionFactory;
}

public static Session getSession(){
return sessionFactory.openSession();
}

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">org.gjt.mm.mysql.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/unionextend</property><!-- ///表示连接本机的数据库//localhost:3306 -->
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">1234</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

<property name="hibernate.hbm2ddl.auto">create</property>
<property name="hibernate.show_sql">true</property>

<mapping resource="blog/hibernate/domain/Employee.hbm.xml"/>
</session-factory>
</hibernate-configuration>

package junit.test;

import java.util.logging.Logger;
import java.util.logging.Level;
import org.hibernate.Transaction;
import blog.hibernate.HibernateUtil;
import blog.hibernate.domain.Employee;
import blog.hibernate.domain.Sale;
import blog.hibernate.domain.Skill;
import org.hibernate.Session;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

public class JoinExtend {

public JoinExtend() {
}

@BeforeClass
public static void setUpClass() throws Exception {
}

@AfterClass
public static void tearDownClass() throws Exception {
}

@Before
public void setUp() {
}

@Test
public void test(){
add();
query();
}

public void add(){
Employee emp1 = new Employee();
emp1.setName("lisi");

Skill emp2 = new Skill();
emp2.setName("wangwu");
emp2.setSkiller("java");

Sale emp3 = new Sale();
emp3.setName("sunliu");
emp3.setSell(300000);

Session session = null;
Transaction tx = null;
try {
session = HibernateUtil.getSession();
tx = session.beginTransaction();
session.save(emp3);
session.save(emp2);
session.save(emp1);
tx.commit();
} catch (Exception e) {
Logger.getLogger(JoinExtend.class.getName()).log(Level.SEVERE, null, e);
if (tx != null) {
tx.rollback();
}
} finally {
if (session != null) {
session.close();
}
}
}

public void query(){
Session session = null;
try {
session = HibernateUtil.getSession();
Employee emp1 = (Employee)session.get(Sale.class, 1);
Employee emp2 = (Employee)session.get(Skill.class, 2);
Employee emp3 = (Employee)session.get(Employee.class, 3);
System.out.println(emp1.toString());
System.out.println(emp2.toString());
System.out.println(emp3.toString());
} catch (Exception e) {
Logger.getLogger(JoinExtend.class.getName()).log(Level.SEVERE, null, e);
} finally {
if (session != null) {
session.close();
}
}
}
}