hibernate 一对一映射的两种方式

一对一映射一共有两种映射方式:



使用用户和***信息的一对一的关系

User:

package cn.itcast.one2one;

public class User {
	private int userId;//用户id
	private String userName;//用户姓名
	private IdCard idCard;//身份者
	public int getUserId() {
		return userId;
	}
	public void setUserId(int userId) {
		this.userId = userId;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public IdCard getIdCard() {
		return idCard;
	}
	public void setIdCard(IdCard idCard) {
		this.idCard = idCard;
	}
	
}

IdCard:

package cn.itcast.one2one;

public class IdCard {
	private int user_id;//
	private  int cardNum;//***号码
	private String place;//出生地
	private User user;
	public int getUser_id() {
		return user_id;
	}
	public void setUser_id(int user_id) {
		this.user_id = user_id;
	}
	public int getCardNum() {
		return cardNum;
	}
	public void setCardNum(int cardNum) {
		this.cardNum = cardNum;
	}
	public String getPlace() {
		return place;
	}
	public void setPlace(String place) {
		this.place = place;
	}
	public User getUser() {
		return user;
	}
	public void setUser(User user) {
		this.user = user;
	}
}

方式一:基于外键模式

User.hbm.xml文件

<?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="cn.itcast.one2one" auto-import="true">
	<class name="User" table="t_user">
		<id name="userId">
			<generator class="native"></generator>
		</id>	
		<property name="userName" length="20"></property>
		<!-- 
			一对一映射： 没有外键方
		 -->
			<one-to-one name="idCard" class="IdCard" cascade="save-update"></one-to-one>
	</class>

</hibernate-mapping>

IdCard.hbm.xml文件

<?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="cn.itcast.one2one" auto-import="true">
	<class name="IdCard" table="t_IdCard">
		<id name="cardNum">
			<generator class="assigned"></generator>
		</id>	
		<property name="place" length="20"></property>
		<!-- 
			一对一映射，有外键方
			unique="true"   给外键字段添加唯一约束
		 -->
		 <many-to-one name="user" unique="true" column="user_id" class="User" cascade="save-update"></many-to-one>
	</class>
</hibernate-mapping>

方式二:基于主键模式

User.hbm.xml(和基于外键模式的一模一样)

<?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="cn.itcast.one2one" auto-import="true">
	<class name="User" table="t_user">
		<id name="userId">
			<generator class="native"></generator>
		</id>	
		<property name="userName" length="20"></property>
		<!-- 
			一对一映射： 没有外键方
		 -->
			<one-to-one name="idCard" class="IdCard" cascade="save-update"></one-to-one>
	</class>

</hibernate-mapping>

IdCard.hbm.xml文件

<?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="cn.itcast.c_one2one2">
	
	<class name="IdCard" table="t_Idcard">
		<id name="user_id">
			<!-- 
				id 节点指定的是主键映射, 即user_id是主键
				主键生成方式： foreign  即把别的表的主键作为当前表的主键；
						property (关键字不能修改)指定引用的对象     对象的全名 cn..User、  对象映射 cn.User.hbm.xml、   table(id)
			 -->
			<generator class="foreign">
				<param name="property">user</param>
			</generator>
		</id>	
		<property name="cardNum" length="20"></property>
		<property name="place" length="20"></property>
		
		<!-- 
			一对一映射，有外键方
			（基于主键的映射）
			 constrained="true"  指定在主键上添加外键约束
		 -->
		<one-to-one name="user" class="User" constrained="true"  cascade="save-update"></one-to-one>
			
	</class>
	
</hibernate-mapping>