Hibernate关联映射 ---一对一案例分析(基于外键)

Hibernate关联映射 ---一对一案例分析(基于外键)

一 概念分析

1．以Person – IdCard为例，Person为主，IdCard为从

一个人只有一个身份证，一个身份证只属于一个人

基于外键的是在从的那一方设置外键并增加一列

二 代码分析

1．Person实例类

package com.hbsi.domain;

public class Person {

private int id;

private String name;

private IdCard idCard; //一个人对应一个身份证

public Person() {

super();

// TODO Auto-generated constructor stub

}

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 IdCard getIdCard() {

return idCard;

}

public void setIdCard(IdCard idCard) {

this.idCard = idCard;

}

}

2．Student实例类

package com.hbsi.domain;

import java.util.Date;

//基于外键的one to one

public class IdCard {

private int id;

private Date usefulLife;

private Person person;//一个身份证只属于一个人

public IdCard() {

super();

// TODO Auto-generated constructor stub

}

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public Date getUsefulLife() {

return usefulLife;

}

public void setUsefulLife(Date usefulLife) {

this.usefulLife = usefulLife;

}

public Person getPerson() {

return person;

}

public void setPerson(Person person) {

this.person = person;

}

}

3．Person的映射文件 Person.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.hbsi.domain">

<class name="Person" table="person">

<id name="id" column="id">

<generator class="native" />

</id>

<property name="name" column="name" />

<!--property-ref 属性的参照,即参照的是person类中的-->

<one-to-one name="idCard" property-ref="person"></one-to-one>

</class>

</hibernate-mapping>

4．IdCard类的映射文件

<?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="com.hbsi.domain">

<class name="IdCard" table="id_card">

<id name="id" column="id">

<generator class="native" />

</id>

<property name="usefulLife" column="useful_life" />

<!-- 基于外键的一对一的映射 和多对一一样，只是多对一可以有重复的部门，而人不可以有重复的身份证，所以要加上unique -->

<many-to-one name="person" column="person_id" unique="true"></many-to-one>

</class>

</hibernate-mapping>

5．测试

public class One2One {

public static void main(String[] args) {

add();

query(1);

}

//保存

static Person add() {

Session session = null;

Transaction transaction = null;

try {

session = HibernateUtil.getSession();

transaction = session.beginTransaction();

IdCard idCard = new IdCard();

idCard.setUsefulLife(new Date());

Person person = new Person();

person.setName("老王");

idCard.setPerson(person);

// person.setIdCard(idCard);

session.save(person);

session.save(idCard);

transaction.commit();

return person;

} finally {

if (session != null) {

session.close();

}

}

}

//查询

static Person query(int person_id) {

Session session = null;

try {

session = HibernateUtil.getSession();

Person person = (Person) session.get(Person.class, person_id);

System.out.println(person.getIdCard().getUsefulLife());

return person;

} finally {

if (session != null) {

session.close();

}

}

}

}