Hibernate之一对一映射

一,概述

前面几篇博客写了一对多 多对多等常见的映射,今天就来写关于一对一映射吧!现实生活中,人与身份信息就是一对一映射.

二,JavaBean设计

1)User.java

package com.bighuan.c_one2one;public class User {private int userId;private String userName;private IdCard idCard;public User() {}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;}@Overridepublic String toString() {return "User [userId=" + userId + ", userName=" + userName+ ", idCard=" + idCard + "]";}public void setIdCard(IdCard idCard) {this.idCard = idCard;}}

2)IdCard.java

package com.bighuan.c_one2one;public class IdCard {private String cardNum;// 主键private String place;private User user;public IdCard() {}public String getCardNum() {return cardNum;}public void setCardNum(String 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;}@Overridepublic String toString() {return "IdCard [cardNum=" + cardNum + ", place=" + place + ", user="+ user + "]";}}

三,基于外键的映射

1)User.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.bighuan.c_one2one"><!-- 对象与表对应 --><class name="User" table="t_user"><id name="userId"><generator class="native" /></id><property name="userName" length="20"></property><!-- 一对一映射:没有外键方 --><one-to-one name="idCard" class="IdCard"></one-to-one></class></hibernate-mapping>

2)IdCard.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.bighuan.c_one2one"><!-- 对象与表对应 --><class name="IdCard" table="t_IdCard"><id name="cardNum"><!-- 手动指定主键 --><generator class="assigned" /></id><property name="place" length="20"></property><!-- 一对一映射:有外键方 unique="true":给外键添加唯一约束--><many-to-one name="user" unique="true" class="User" column="user_id" cascade="save-update"></many-to-one></class></hibernate-mapping>

四,测试一

1)代码

package com.bighuan.c_one2one;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.junit.Test;public class App {private static SessionFactory sf;static {sf = new Configuration().configure().addClass(IdCard.class).addClass(User.class)// 测试时用.buildSessionFactory();}@Testpublic void testSave() throws Exception {// 获得sessionorg.hibernate.Session session = sf.openSession();session.beginTransaction();//用户User user=new User();user.setUserName("Leslie");//身份证IdCard idCard=new IdCard();idCard.setCardNum("360732XXX");idCard.setPlace("江西南昌");//关系idCard.setUser(user);//保存session.save(idCard);session.getTransaction().commit();session.close();}}

2)结果

用户表有两个字段:userId userName,身份证表有三个字段:cardNum place user_id,第一个字段为主键.

五,基于主键的映射

1)User.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.bighuan.c_one2one2"><!-- 对象与表对应 --><class name="User" table="t_user"><id name="userId"><generator class="native" /></id><property name="userName" length="20"></property><!-- 一对一映射:没有外键方 --><one-to-one name="idCard" class="IdCard"></one-to-one></class></hibernate-mapping>

2)IdCard.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.bighuan.c_one2one2"><!-- 对象与表对应 --><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="place" length="20"></property><property name="cardNum" 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>

六,测试二

1)代码

package com.bighuan.c_one2one2;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.junit.Test;public class App {private static SessionFactory sf;static {sf = new Configuration().configure().addClass(IdCard.class).addClass(User.class)// 测试时用.buildSessionFactory();}@Testpublic void testSave() throws Exception {// 获得sessionorg.hibernate.Session session = sf.openSession();session.beginTransaction();//用户User user=new User();user.setUserName("Leslie111");//身份证IdCard idCard=new IdCard();idCard.setCardNum("360732XXXYYYY");idCard.setPlace("江西南昌");//关系idCard.setUser(user);//保存session.save(idCard);session.getTransaction().commit();session.close();}}

2)结果

用户表有两个字段:userId userName,身份证表有三个字段:user_id cardNum place ,第一个字段为主键.

七,总结

两种映射方式生成的表有一点区别,主要是身份证表的主键不一样.