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();
}
}
}
}