组件映射、继承映射

一、组件映射

1.概念

类组合关系的映射，也叫作组件映射！
注意：组件类和被包含的组件类，共同映射到一张表！

2.需求

汽车与车轮

3.数据库T_Car

主键 汽车名称 轮子大小 个数

4.Car

/**
 * Created by qianxingzhe on 16/5/28.
 */
public class Car {
    private int id;

    private String name;

    private Wheel wheel;

    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 Wheel getWheel() {
        return wheel;
    }

    public void setWheel(Wheel wheel) {
        this.wheel = wheel;
    }
}

5.Wheel

/**
 * Created by qianxingzhe on 16/5/28.
 */
public class Wheel {

    private int count;

    private int size;

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    public int getSize() {
        return size;
    }

    public void setSize(int size) {
        this.size = size;
    }
}

6.Car.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.yly.component">

    <class name="Car" table="t_car">
        <id name="id">
            <generator class="native">
            </generator>
        </id>

        <property name="name" length="20"/>

        <!--
        组件映射
        -->
        <component name="wheel" class="Wheel">
            <property name="size"></property>
            <property name="count"></property>
        </component>

    </class>

</hibernate-mapping>

二、继承映射

1.简单继承映射

有多少个子类，写多少个映射文件！

2.简单继承代码

// 动物类
public abstract class Animal {

	private int id;
	private String name;
}	

<!-- 
	简单继承
 -->
<hibernate-mapping package="cn.itcast.e_extends1">
	
	<class name="Cat" table="t_Cat">
		<!-- 简单继承映射： 父类属性直接写 -->
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="na"></property>
		<property name="catchMouse"></property>					 
	</class>
	

</hibernate-mapping>

@Test
	public void getSave() {
		
		Session session = sf.openSession();
		session.beginTransaction();
		
		// 保存
//		Cat cat = new Cat();
//		cat.setName("大花猫");
//		cat.setCatchMouse("抓小老鼠");
//		session.save(cat);
		
		// 获取时候注意：当写hql查询的使用，通过父类查询必须写上类的全名
		Query q = session.createQuery("from cn.itcast.e_extends1.Animal");
		List<Animal> list = q.list();
		System.out.println(list);
		
		session.getTransaction().commit();
		session.close();
		
	}
	

继承映射

1.所有子类映射到一张表
2.每个类映射到一张表
3.每个子类映射一张表，父类不对应表