Hibernate 继承关系配置

第一种情况：Hibernate 继承关系每个子类一张表

Person.java

package com.wansha.pojo;

public class Person {
	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;
	}
}

Student.java

package com.wansha.pojo;

public class Student extends Person{
	private String cardId;

	public String getCardId() {
		return cardId;
	}

	public void setCardId(String cardId) {
		this.cardId = cardId;
	}
}

Teacher.java

package com.wansha.pojo;

public class Teacher  extends Person{
	private int salary;

	public int getSalary() {
		return salary;
	}

	public void setSalary(int salary) {
		this.salary = salary;
	}
}

Teacher.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
	<class name="com.wansha.pojo.Teacher" table="teacher">
		<id name="id" column="id" type="int">
			<generator class="identity"></generator>
		</id>
		<property name="name" column="name" type="string" />
		<property name="salary" column="salary" type="int" />
	</class>
</hibernate-mapping>

Student.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
	<class name="com.wansha.pojo.Student" table="student">
		<id name="id" column="id" type="int">
			<generator class="identity"></generator>
		</id>
		<property name="name" column="name" type="string" />
		<property name="cardId" column="cardId" type="string" />
	</class>
</hibernate-mapping>  

第二种情况：Hibernate 继承关系所有子类一张表

Person.hbm.xml 只有person.hbm.xml一个配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
	<class name="com.wansha.pojo.Person" table="person">
		<id name="id" column="id" type="int">
			<generator class="identity"></generator>
		</id>
		<discriminator column="type" type="string" />
		<property name="name" column="name" type="string" />
		<subclass name="com.wansha.pojo.Student" discriminator-value="student">
			<property name="cardId" column="cardId" type="string"/>
		</subclass>
		<subclass name="com.wansha.pojo.Teacher" discriminator-value="teacher">
			<property name="salary" column="salary" type="int"/>
		</subclass>
	</class>
</hibernate-mapping>

Test.java

package com.wansha.util;

import java.util.List;

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

import com.wansha.pojo.Student;
import com.wansha.pojo.Teacher;

public class Test {
	public static void main(String[] args) {
/*		Student student = new Student();
		student.setName("sharp");
		student.setCardId("111111");
		
		Teacher teacher = new Teacher();
		teacher.setName("teacher zhang");
		teacher.setSalary(800);
		
		Session session = HibernateUtil.getSession();
		Transaction ts = null;
		try{
			ts = session.beginTransaction();
			session.save(student);
			session.save(teacher);
			ts.commit();
		}catch(Exception ex){
			if(ts != null)ts.rollback();
			ex.printStackTrace();
		}finally{
			HibernateUtil.close(session);
		}*/
		
		
		
		Session session = HibernateUtil.getSession();
		Transaction ts = null;
		try{
			ts = session.beginTransaction();
			List list = session.createQuery("from Person").list();
			for(Object object : list){
				if(object instanceof Student){
					Student student = (Student)object;
					System.out.println(student.getCardId());
				}else if(object instanceof Teacher){
					Teacher teacher = (Teacher)object;
					System.out.println(teacher.getSalary());
				}
			}
			ts.commit();
		}catch(Exception ex){
			if(ts != null)ts.rollback();
			ex.printStackTrace();
		}finally{
			HibernateUtil.close(session);
		}
	}

}

第三种情况：父类一张表，每个子类一张表，父类的表保存公共有信息，子类的表只保存自己特有的信息

Person.hbm.xml 也是只需要一个配置文件，其它页面与第二种情况一样

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping>
	<class name="com.wansha.pojo.Person" table="person">
		<id name="id" column="id" type="int">
			<generator class="identity"></generator>
		</id>
		<property name="name" column="name" type="string" />
		<joined-subclass name="com.wansha.pojo.Student" table="student">
			<key column="id"/>
			<property name="cardId" column="cardId" type="string" />
		</joined-subclass>
		<joined-subclass name="com.wansha.pojo.Teacher" table="teacher">
			<key column="id"/>
			<property name="salary" column="salary" type="int" />
		</joined-subclass>
	</class>
</hibernate-mapping>