18_高级映射：一对一查询（使用resultMap）

package cn.higgin.mybatis.po;import java.util.Date;public class User {
//属性名和数据库表的字段对应
private int id;
private String username;
private String sex;
private Date birthday;
private String address;
//省略get/set方法
}

package cn.higgin.mybatis.po;import java.util.Date;public class Orders { private Integer id;
private Integer userId;
private String number;
private Date createtime;
private String note;
//注意!!!这里引入了User
private User user; //省略get/set方法......
}

package cn.higgin.mybatis.mapper;import java.util.List;import cn.higgin.mybatis.po.Orders;public interface OrdersMapperCustom { //查询订单关联查询用户信息,使用resultMap方式
public List<Orders> findOrdersUserResultMap() throws Exception;
}

<?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="cn.higgin.mybatis.mapper.OrdersMapperCustom"> <!--
订单查询关联用户的resultMap
将整个查询的结果映射到cn.higgin.mybatis.po.Orders中
-->
<resultMap type="cn.higgin.mybatis.po.Orders" id="OrdersUserResultMap">
<!-- 配置订单的映射信息 -->
<!--
id:指定查询列中的唯一标识，订单信息中的唯一标识，若有多个列组成唯一标识，需配置多个id
column: 订单信息的唯一标识列
property: 订单信息的唯一标识列所映射到的 Orders的对应的属性
-->
<id column="id" property="id"/>
<result column="user_id" property="userId"/>
<result column="number" property="number" />
<result column="createtime" property="createtime"/>
<result column="note" property="note" /> <!-- 配置映射的关联的用户信息 -->
<!-- association：用于映射关联查询单个对象的信息
property：要将关联查询的用户信息映射到Orders中的对应属性
-->
<association property="user" javaType="cn.higgin.mybatis.po.User">
<!--
id：关联查询用户的唯一标识
column：指定唯一标识用户信息的列
javaType：映射到user的对应属性
-->
<id column="user_id" property="id"/>
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>
</association>
</resultMap> <!-- 查询订单关联查询用户信息，使用resultMap -->
<select id="findOrdersUserResultMap" resultMap="OrdersUserResultMap">
SELECT
orders.*,
USER.username,
USER.sex,
USER.address
FROM
orders,USER
WHERE orders.user_id=user.id
</select> </mapper>

package cn.higgin.mybatis.mapper;import java.io.InputStream;
import java.util.List;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Before;
import org.junit.Test;import cn.higgin.mybatis.po.Orders;public class OrdersMapperCustomTest {
private SqlSessionFactory sqlSessionFactory; // 此方法是在执行testFindUserById之前执行
@Before
public void setUp() throws Exception {
// 创建sqlSessionFactory // mybatis配置文件
String resource = "SqlMapConfig.xml";
// 得到配置文件流
InputStream inputStream = Resources.getResourceAsStream(resource); // 创建会话工厂，传入mybatis的配置文件信息
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
}
@Test
public void testFindOrdersUser() throws Exception {
SqlSession sqlSession=sqlSessionFactory.openSession();
//创建代理对象
OrdersMapperCustom ordersMapperCustom=sqlSession.getMapper(OrdersMapperCustom.class); //调用mapper的方法
List<Orders> list=ordersMapperCustom.findOrdersUserResultMap(); System.out.println(list.size()); sqlSession.close(); }}