Hibernate关系映射（一） 基于外键的单向一对一

模拟用户和地址的映射关系，一个用户只有一个地址，用户知道地址，但是地址不知道用户。用户对地址的单向一对一映射。

一、建立实体类

Account.cs类

package com.lxit.entity;

import java.io.Serializable;

public class Account implements Serializable{
public Account(){

}
private int id;
private String name;
private String password;
//需要添加被控端的引用
private Address address;

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 String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}

}

Address.cs类 地址类

package com.lxit.entity;

import java.io.Serializable;

public class Address implements Serializable{
public Address(){

}
private int id;
private String name;

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;
}

}

二、映射文件

Account.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.lxit.entity.Account" table="Account">
<id column="id" name="id">
<generator class="native"/>
</id>
<property column="name" generated="never" lazy="false" name="name"/>
<property column="password" generated="never" lazy="false" name="password"/>
<!-- 通过many-to-one 标签添加唯一属性约束，建立一对一关联关系 -->
<many-to-one column="address_id" name="address" unique="true"/>
<!-- 必须通过映射关系生成的表才会生成唯一约束，否则不会生成 -->
</class>
</hibernate-mapping>

Address.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.lxit.entity.Address" table="Address">
<id column="id" name="id">
<generator class="native"/>
</id>
<property column="name" generated="never" lazy="false" name="name"/>
</class>
</hibernate-mapping>

三、HibernateUtil工具类

package com.lxit.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

/**
* Hibernate3.3工具类
* @author Administrator
*
*/
public class HibernateUtil {
private static SessionFactory factory;

static{
Configuration cfg = new Configuration().configure();
factory = cfg.buildSessionFactory();
}

public static SessionFactory getFactory(){
return factory;
}

public static Session getSession(){
return factory.openSession();
}

public static void CloseSession(Session session){
if(session != null){
session.close();
}
}
}

四、hibernate.cfg.xml配置文件

<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory name="foo">
<!-- 配置数据库连接 -->
<property name="hibernate.dialect">
org.hibernate.dialect.MySQL5Dialect
</property>
<property name="hibernate.connection.driver_class">
com.mysql.jdbc.Driver
</property>
<property name="hibernate.connection.url">
jdbc:mysql://127.0.0.1:3306/test
</property>
<property name="hibernate.connection.username">root</property>
<property name="hibernate.connection.password">root</property>

<property name="show_sql">true</property>
<property name="format_sql">true</property>

<property name="hbm2ddl.auto">update</property>
<mapping resource="com/lxit/entity/Account.hbm.xml" />
<mapping resource="com/lxit/entity/Address.hbm.xml" />

</session-factory>
</hibernate-configuration>

五、Jutil测试类

package com.lxit.demo2.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.lxit.entity.Account;
import com.lxit.entity.Address;
import com.lxit.util.HibernateUtil;

public class AccountTest {

@Test
public void Add(){
Transaction tx = null;
Session session = HibernateUtil.getSession();
tx = session.beginTransaction();

Address address= new Address();
address.setName("深圳宝安");
session.save(address);

Account account = new Account();
account.setName("zhangsan");
account.setPassword("123");
account.setAddress(address);

try {
session.save(account);
tx.commit();
} catch (Exception e) {
e.printStackTrace();
tx.rollback();
}finally{
HibernateUtil.CloseSession(session);
}
}

@Test
public void Add2(){
Transaction tx = null;
Session session = HibernateUtil.getSession();
tx = session.beginTransaction();

Address address= new Address();
address.setName("深圳福田");
session.save(address);

Account account1 = new Account();
account1.setName("lisi");
account1.setPassword("123");
account1.setAddress(address);

Account account2 = new Account();
account2.setName("wangwu");
account2.setPassword("123");
account2.setAddress(address);

try {
//重复添加第二个用户，地址相同，则会报错
session.save(account1);
session.save(account2);
tx.commit();
} catch (Exception e) {
e.printStackTrace();
tx.rollback();
}finally{
HibernateUtil.CloseSession(session);
}
}
}

总结：单向一对一必须通过实体类生成数据库表的方式，会自动生成相关的约束，直接创建表无效。