hibernate annotation 双向 one-to-one 注解

package com.hibernate.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Husband implements Serializable {


    /**
     *
     */
    private static final long serialVersionUID = 2476364405175138004L;


    private int id;

    private String name;

    private Wife wife;


    @Id
    @GeneratedValue
    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    @OneToOne
    public Wife getWife() {
        return wife;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setWife(Wife wife) {
        this.wife = wife;
    }


}

 

 

package com.hibernate.entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife implements Serializable {

    /**
     *
     */
    private static final long serialVersionUID = 5270130768836331730L;


    private int id;

    private String name;

    private Husband husband;


    @Id
    @GeneratedValue
    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;
    }

    @OneToOne(mappedBy="wife")
    public Husband getHusband() {
        return husband;
    }

    public void setHusband(Husband husband) {
        this.husband = husband;
    }

}

 

注意：Wife类的getHusband()上用了mappedBy"wife"

这个意思是说，我这里的OneToOne就不用管了，只用Husband里的getWife()上的OneToOne关系

生成的表为Husband参考Wife，有了wifeid，才能有Husband

Husband为这个关系的拥有者

 

如果Wife类的getHusband()只有@OneToOne，没有mappedBy，那么生成的两张表都会有对方的外键，造成外键冗余。

Test.java

package com.fancy.test;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.cfg.Configuration;
import com.fancy.po.Card;
import com.fancy.po.Person;
/**
 * -----------------------------------------
 * @文件: Test.java
 * @作者: fancy
 * @邮箱: fancyzero@yeah.net
 * @时间: 2012-6-10
 * @描述: 测试类
 * -----------------------------------------
 */
public class Test {

    public static void main(String[] args) {
        
        //读取hibernate配置,默认读取classpath下的hibernate.cfg.xml
        Configuration conf = new AnnotationConfiguration();    
        //构建session工厂
         SessionFactory sessionFactory = conf.configure().buildSessionFactory();
        //打开session
        Session session = sessionFactory.openSession();
        //开始事务
         session.beginTransaction();
        // * * * * * * * * * * * * * * * * * * * * * * * * * * * *
        //test1(session);    //测试 1
        //test2(session);    //测试 2
        test3(session);      //测试 3
        // * * * * * * * * * * * * * * * * * * * * * * * * * * * *
        //提交事务
         session.getTransaction().commit();
        //关闭session工厂
         sessionFactory.close();
       //关闭session
       session.close();
    }
    /**
     * 数据库初始值：
      * personName：fancy
     * cardNumber：440911199008011122
     */
    //测试方法1
    public static void test1(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancy");            //与初始值一致
         card.setCardNumber("440911199008011122");//与初始值一致
         session.save(person);    //不发出sql语句
       //session.save(card);     //不发出sql语句
    }
    //测试方法2
    public static void test2(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancyzero");        //与初始值不一致
         card.setCardNumber("440911199008011122");//与初始值一致
         session.save(person);    //发出Person的update语句,数据库中personName被修改,不发出Card的update语句
       //session.save(card);     //发出Person的update语句,数据库中personName被修改,不发出Card的update语句
    }
    //测试方法3
    public static void test3(Session session){
        Person person = (Person)session.get(Person.class, 1); //发出Person和Card的select语句
         Card card = person.getCard();
        System.out.println(person.getPersonName());
        System.out.println(card.getCardNumber());
        person.setPersonName("fancy");           //与初始值不一致
         card.setCardNumber("440911199008080808");//与初始值不一致
         session.save(person);    //同时发出Person和Card的update语句,数据库中的数据相应被修改
       //session.save(card);     //同时发出Person和Card的update语句,数据库中的数据相应被修改
    }
}