hibernate一对一映射

hibernate中一对一映射举个例子就是个人（User）与身份证（IdCard）的关系。

1、创建实体类User.java

package cn.itcast.a;public class User {private int userId;private String userName;private IdCard idCard;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;}}

2、创建实体类IdCard.java

package cn.itcast.a;public class IdCard {private int userId;private String cardNum;private String palce;private User user;public int getUserId() {return userId;}public void setUserId(int userId) {this.userId = userId;}public String getCardNum() {return cardNum;}public void setCardNum(String cardNum) {this.cardNum = cardNum;}public String getPalce() {return palce;}public void setPalce(String palce) {this.palce = palce;}public User getUser() {return user;}public void setUser(User user) {this.user = user;}}

3、配置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="cn.itcast.a"><!--name为实体类的名称    table为表名  --><class name="User" table="t_user"><!-- 主键字段 --><!-- name为实体类中的属性名 --><id name="userId"><!-- native为自增长 --><generator class="native"></generator></id><!-- 其他字段 --><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>

4、配置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="cn.itcast.a"><!--name为实体类的名称    table为表名  --><class name="IdCard" table="t_idCard"><!-- 主键字段 --><!-- name为实体类中的属性名 --><id name="userId"><!--id 节点指定的是主键映射，即userId是主键主键生成方式：foreign 即把别的表的主键最为当前表的主键：property（关键字不能修改）指定引用的对象 --><generator class="foreign"><param name="property">user</param></generator></id><!-- 其他字段 --><property name="cardNum" length="20"></property><property name="palce" 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>

5、配置hibernate.cfg.xml

<!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><property name="show_sql">true</property><!-- 数据库连接配置 --><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.url">jdbc:mysql:///employee</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password">123456</property><property name="dialect">org.hibernate.dialect.MySQL5Dialect</property><!-- 其他相关配置 --><!-- 显示hibernate在运行时执行的sql语句 --><property name="hibernate.show_sql">true</property><!-- 格式化sql --><property name="hibernate.format_sql">true</property><!-- 自动建表 --><property name="hibernate.hbm2ddl.auto">update</property><!-- 加载所有映射 --><mapping resource="cn/itcast/a/IdCard.hbm.xml"/><mapping resource="cn/itcast/a/User.hbm.xml"/></session-factory></hibernate-configuration>

6、创建测试类App.java

package cn.itcast.a;import static org.junit.Assert.*;import org.hibernate.Session;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().buildSessionFactory();}@Testpublic void test() {Session session=sf.openSession();session.beginTransaction();User user = new User();user.setUserName("张三");IdCard idcard = new IdCard();idcard.setCardNum("420113");idcard.setPalce("武汉");idcard.setUser(user);session.save(user);session.save(idcard);session.getTransaction().commit();session.close();}}

7、项目结构图为