继承关系_整个继承树映射到一张表_每个类映射到一张表_鉴别器与内连接相结合(混合)_每个具体类映射一张独立表

整个继承树映射到一张表_每个类映射到一张表_鉴别器与内连接相结合(混合)_每个具体类映射一张独立表

 整个继承树映射到一张表

描述：
在父类的配置文件中

1、添加<discriminator column="字段名字" type="字段类型" />鉴别器标签

column="type"给Hibernate使用，type属性设置column的类型，默认String

2、配置子类

  <subclass name="Skiller" discriminator-value="1"> name="类名"  discriminator-value="类对应的鉴别字段的数值"
   <property name="skill" />
  </subclass>

3、父类也要添加鉴别器值

 <class name="Employee" discriminator-value="0">

 

 

表结构

 

实例代码

Sales.java继承自Employee

package com.dwt1220;

public class Sales extends Employee {
	private String sell;

	public String getSell() {
		return sell;
	}

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

Skiller.java继承自Employee

package com.dwt1220;

public class Skiller extends Employee{
	private String skill;

	public String getSkill() {
		return skill;
	}

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

Employee.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.dwt1220">

	<class name="Employee" discriminator-value="0">
		<id name="id">
			<generator class="native" />
		</id>
		<!--鉴别器column="type"给Hibernate使用，type属性默认String -->
		<discriminator column="type" type="int" />

		<property name="name" />
		<many-to-one name="department" column="depart_id" />

		<subclass name="Skiller" discriminator-value="1">
			<property name="skill" />
		</subclass>

		<subclass name="Sales" discriminator-value="2">
			<property name="sell" />
		</subclass>
	</class>

</hibernate-mapping>

Test.java

package com.dwt1220;

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

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

public class Test {
	public static void main(String[] args) {

		Employee employee1 = new Employee();
		employee1.setName("employee1_D1");

		Employee employee2 = new Employee();
		employee2.setName("employee2_D1");

		/********* Employee子类 *************/
		Sales sales = new Sales();
		sales.setName("sales01");
		sales.setSell("sales_sub");

		Skiller skiller = new Skiller();
		skiller.setName("skiller01");
		skiller.setSkill("skill_sub");
		/**********************************/

		Department department1 = new Department();
		department1.setName("Department1");
		add(department1);
		
		Set<Employee> employees = new HashSet<Employee>();
		employees.add(employee1);
		employees.add(employee2);

		/********* 添加子类 ************/
		employees.add(sales);
		employees.add(skiller);
		/**********************************/
		
		department1.setEmployee(employees);
		add(employee1);
		add(employee2);

		/********* 添加子类到数据库 ************/
		add(sales);
		add(skiller);
		/**********************************/
		
		getEmployee(2);
	}

	static void add(Object object) {
		Session session = null;
		Transaction tx = null;
		try {
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();
			session.save(object);
			tx.commit();
		} catch (HibernateException e) {
			if (tx != null) {
				tx.rollback();
			}
			throw e;
		} finally {
			if (session != null) {
				session.close();
			}
		}
	}

	static Department getDepartment(int id) {
		Session session = null;
		Department department = null;
		try {
			session = HibernateUtil.getSession();
			department = (Department) session.get(Department.class, id);

			/** 懒加载，所以要在Session关闭前使用。 */
			System.out.println("department:id=" + department.getId()
					+ "    department:name=" + department.getName());
			Set<Employee> employeeSet = (Set<Employee>) department
					.getEmployee();
			for (Employee employee : employeeSet) {
				System.out.println("employee:id=" + employee.getId()
						+ "     employee:name=" + employee.getName());
			}

		} finally {
			if (session != null) {
				session.close();
			}
		}
		return department;
	}

	static Employee getEmployee(int id) {
		Session session = null;
		Employee employee = null;
		try {
			session = HibernateUtil.getSession();
			employee = (Employee) session.get(Employee.class, id);

			/** 懒加载，所以要在Session关闭前使用。 */
			System.out.println(employee);

		} finally {
			if (session != null) {
				session.close();
			}
		}
		return employee;
	}

}

 

每个类映射到一张表(只需修改配置文件)

多态查找时，需要查找所有子类表。效率低。查询时最好，直接指定子类的类型，尽量不要用多态超找

描述

在父类配置文件中，添加子类信息

  <joined-subclass name="Skiller" table="skiller">
          <key column="emp_id" /> emp_id，字段名，与父类的主键值相同。可以随意设置，hibernate管理
          <property name="skill" />
  </joined-subclass>

Employee.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.dwt1220">

	<class name="Employee">
		<id name="id">
			<generator class="native" />
		</id>

		<property name="name" />
		<many-to-one name="department" column="depart_id" />

		<joined-subclass name="Skiller" table="skiller">
			<key column="emp_id" />
			<property name="skill" />
		</joined-subclass>

		<joined-subclass name="Sales" table="sales">
			<key column="emp_id" />
			<property name="sell" />
		</joined-subclass>

	</class>
</hibernate-mapping>

 鉴别器与内连接相结合

※先把相关的表删除，不然可能出错

子类和父类公用一张表设置

1、添加<discriminator column="字段名字" type="字段类型" />鉴别器标签

column="type"给Hibernate使用，type属性设置column的类型，默认String

2、配置子类

  <subclass name="Skiller" discriminator-value="1"> name="类名"  discriminator-value="类对应的鉴别字段的数值"
   <property name="skill" />
  </subclass>

3、父类也要添加鉴别器值(混合)

 <class name="Employee" discriminator-value="0">

单独表设置

  <!--discriminator-value="2"，不设置，默认值为表名，类型字符串  -->
  <subclass name="Sales" discriminator-value="2">
             <join table="sales">
                    <key column="emp_id" />
                    <property name="sell" />
             </join>
  </subclass>

 

 

Employee.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.dwt1220">

	<class name="Employee" discriminator-value="0">
		<id name="id">
			<generator class="native" />
		</id>
		<discriminator column="type" type="int" />

		<property name="name" />
		<many-to-one name="department" column="depart_id" />

		<subclass name="Skiller" discriminator-value="1">
			<property name="skill" />
		</subclass>

		<!--discriminator-value="2"，不设置，默认值为表名，类型字符串  -->
		<subclass name="Sales" discriminator-value="2">
			<join table="sales">
				<key column="emp_id" />
				<property name="sell" />
			</join>
		</subclass>
	</class>

</hibernate-mapping>

 

每个具体类映射一张独立表

1、父类的id生成方式需要修改  <generator class="hilo" />

2、配置子类

   <union-subclass name="Skiller" table="skiller">
         <property name="skill"></property>
   </union-subclass>

Employee.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.dwt1220">

	<class name="Employee" >
		<id name="id">
			<generator class="hilo" />
		</id>

		<property name="name" />
		<many-to-one name="department" column="depart_id" />

		<union-subclass name="Skiller" table="skiller">
			<property name="skill"></property>
		</union-subclass>

		<union-subclass name="Sales" table="sales">
			<property name="sell"></property>
		</union-subclass>
		
	</class>

</hibernate-mapping>