一對一關係推薦使用唯一主外來鍵關聯，即兩個表使用外來鍵關聯，由於是一對一關聯，因此還需要給外來鍵增加unique唯一約束。

下面我們以每個人只有一張身份證，一個身份證對應一個人為例。

1、在資料庫mybatis中新建兩張表，並插入一條資料，表結構如下：

表資料如下：

2、在mybatis專案中的pojo目錄下新建與兩個表相對應的pojo物件。

package pojo;

import java.io.Serializable;

public class Card implements Serializable{

	private Integer id;
	private String code;
	public Card(){}
	public Card(String code){
		this.code = code;
	}
	
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getCode() {
		return code;
	}
	public void setCode(String code) {
		this.code = code;
	}
}
 

package pojo;

import java.io.Serializable;

public class Person implements Serializable{

	private Integer id;
	private String name;
	private Card card;
	public Person(){}
	public Person(String name,Card card){
		this.name = name;
		this.card = card;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Card getCard() {
		return card;
	}
	public void setCard(Card card) {
		this.card = card;
	}
}
 

3、在mapping目錄下新建兩個物件的對映檔案

mapping/CardMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapping.CardMapper">
	<select id="selectCardById" parameterType="int" resultType="pojo.Card">
		select*from card where id = #{id}
	</select>
</mapper>
 

mapping/PersonMapper.xml，在這裡使用了<association/>元素對映一對一的關聯關係，select屬性表示會使用column屬性的card_id值作為引數執行CardMapper中定義的selectCardById查詢對的Card資料，查詢出的資料將封裝到property表示的card物件當中

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapping.PersonMapper">
	<!-- 設定返回的物件 -->
	<resultMap type="pojo.Person" id="personResult">
		<id property="id" column="id"/>
		<result property="name" column="name"/>
		<!-- 一對一關聯 select的值對應CardMapper.xml的名稱空間+select的id-->
		<association property="card" column="card_id" javaType="pojo.Card" select="mapping.CardMapper.selectCardById"/>
	</resultMap>
	<!-- 查詢person -->
	<select id="selectPersonById" parameterType="int" resultMap="personResult">
		select*from person where id = #{id}
	</select>
</mapper>

4、編寫mapper介面，與mapper對映檔案在同級目錄下。注意，這裡的類名需與配置檔案中的namespace一致，而方法名和引數也必須與xml檔案中<select/>標籤的id屬性和parameterType屬性一致，

package mapping;

import pojo.Person;

public interface PersonMapper {

	Person selectPersonById(Integer id);
}

5、在mybatis-config配置檔案下宣告剛剛建立的兩個對映檔案

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 指定所有日誌的具體實現 -->
	<settings>
		<setting name="logImpl" value="LOG4J"/>
	</settings>
	<!-- 環境配置 -->
	<environments default="mysql">
		<environment id="mysql">
			<!-- 指定事務管理型別 -->
			<transactionManager type="JDBC" />
			<!-- 配置資料來源，POOLED是JDBC連線物件的資料來源連線池的實現 -->
			<dataSource type="POOLED">
				<property name="driver" value="com.mysql.jdbc.Driver"/>
				<property name="url" value="jdbc:mysql://localhost:3306/mybatis"/>
				<property name="username" value="root"/>
				<property name="password" value="root"/>
			</dataSource>
		</environment>
	</environments>
	<!-- mappers告訴mybatis找持久化類的對映檔案 -->
	<mappers>
		<mapper resource="mapping/UserMapper.xml"/>
		<mapper resource="mapping/PersonMapper.xml"/>
		<mapper resource="mapping/CardMapper.xml"/>

	</mappers>
</configuration>

6、編寫一個工廠類用於讀取mybatis-config配置檔案並生成對應的SqlSession

package factory;

import java.io.IOException;
import java.io.InputStream;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class MyFactory {

	private static SqlSessionFactory ssf = null;
	static{
		try {
			InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
			ssf = new SqlSessionFactoryBuilder().build(is);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	//獲取SqlSession的靜態方法
	public static SqlSession getSqlSession(){
		return ssf.openSession();
	}
	//獲取SqlSessionFactory的靜態方法
		public static SqlSessionFactory getSqlSessionFactory(){
			return ssf;
		}
}

7、編寫一對一的測試類

package reflectTest;

import org.apache.ibatis.session.SqlSession;

import factory.MyFactory;
import mapping.PersonMapper;
import pojo.Person;

public class OneToOne {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		SqlSession session = MyFactory.getSqlSession();
		PersonMapper pm = session.getMapper(PersonMapper.class); //通過代理物件訪問
		Person p = pm.selectPersonById(1); //查詢id為1的person資訊
		System.out.println(p.getId()+":"+p.getName());
		System.out.println(p.getCard().getId()+":"+p.getCard().getCode());
		session.commit();
		session.close();
	}

}

執行結果：

注意：mapper的介面代理物件一定要與對映檔案處於同一級目錄，否則會報錯