MyBatis一对一查询使用ResultType映射

需求背景：查询订单信息关联用户信息。

mapper.xml

<!DOCTYPE mapper
    PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
    "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.hl.mybatis.first.mapper.OrdersCustomMapper">

    <!-- 定义查询订单关联查询用户ResultMap 
        com.hl.myabtis.first.beas.Orders将整个查询的信息映射到Order上
    -->
    <resultMap type="com.hl.myabtis.first.beas.Orders" id="ordersUserResultMap">
        <!-- 配置Order映射信息
            id：订餐结果集唯一标识
            property：对应订单类属性
         -->
        <id column="id" property="id"/>
        <result column="user_id" property="user_id"/>
        <result column="number" property="number"/>
        <result column="createtime" property="createtime"/>
        <result column="note" property="note"/>
        <!-- 配置关联属性User的映射信息
            association:用于映射关联查询单个对象的信息
            property：用户信息所要映射到的属性名
            user：属性的全类名
         -->
        <association property="user" javaType="com.hl.myabtis.first.beas.User">
        <!-- 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的对应属性类型
        -->
            <id column="user_id" javaType="java.lang.Integer"/>
            <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 -->
    <select id="findOrdersUser" resultType="com.hl.myabtis.first.beas.OrdersCustom">
        select orders.*,user.username,user.sex,user.address from orders,user where orders.user_id = user.id
    </select>   


    <!-- 查询订单关联查询用户信息  ResultMap映射-->
    <select id="findOrdersUserResultMap" resultMap="ordersUserResultMap">
        select orders.*,user.username,user.sex,user.address from orders,user where orders.user_id = user.id
    </select>   
</mapper>

mapepr.java

package com.hl.mybatis.first.mapper;

import java.util.List;

import com.hl.myabtis.first.beas.Orders;
import com.hl.myabtis.first.beas.OrdersCustom;


public interface OrdersCustomMapper {
    //查询订单关联用户信息
    public List<OrdersCustom> findOrdersUser() throws Exception;
    //查询订单关联用户信息ResultMap
    public List<Orders> findOrdersUserResultMap() throws Exception;

}

原始订单类：

package com.hl.myabtis.first.beas;

import java.util.Date;

public class Orders {

    private Integer id;

    private Integer user_id;

    private String number;

    private Date createtime;

    private String note;

    //用户信息
    private User user;
    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getUserId() {
        return user_id;
    }

    public void setUserId(Integer userId) {
        this.user_id = userId;
    }

    public String getNumber() {
        return number;
    }

    public void setNumber(String number) {
        this.number = number;
    }

    public Date getCreatetime() {
        return createtime;
    }

    public void setCreatetime(Date createtime) {
        this.createtime = createtime;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }
    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    @Override
    public String toString() {
        return "Orders [id=" + id + ", user_id=" + user_id + ", number="
                + number + ", createtime=" + createtime + ", note=" + note
                + ", user=" + user + "]";
    }

}

测试代码：

@Test
    public void testFindOrdersUserResultMap() throws Exception{
        SqlSession sqlSession = sqlSessionFactory.openSession();
        OrdersCustomMapper ordersMapper = sqlSession.getMapper(OrdersCustomMapper.class);
        List<Orders> list = ordersMapper.findOrdersUserResultMap();
        for (Orders ordersCustom : list) {
            System.out.println(ordersCustom);
        }
    }

对比：MyBatis一对一查询使用ResultType映射 ；不同的是将User作为一个属性存在Orders类中。