mybatis多对一嵌套结果-mybatis学习笔记05

电玩女神 2022-04-08 12:30 235阅读 0赞

mybatis多对一嵌套结果：  
多对一嵌套结果的特点就是：只发送一条sql语句：  
![在这里插入图片描述][2018121323434662.png]  
步骤：  
新建domain类：  
![在这里插入图片描述][20181213233403482.png]![在这里插入图片描述][20181213233430280.png]新建一个domainMapper接口类：  
![在这里插入图片描述][20181213233512359.png]配置domainMapper.xml文件：这里是EmployeeMapper.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="cn.itsource.mybatis.manytoone_02.EmployeeMapper">
    
        <select id="findAll" resultMap="EmployeeMap">
            select e.id,e.username,e.age,e.dept_id,d.id did,d.name dname from employee e left join department d on e.dept_id=d.id
        </select>
    
        
        <resultMap id="EmployeeMap" type="cn.itsource.mybatis.manytoone_02.Employee">
    
            <id column="id" property="id"/>
            <result column="username" property="username"/>
            <result column="age" property="age"/>
    
            <association property="department"
                         javaType="cn.itsource.mybatis.manytoone_02.Department"
                         >
    
                <id column="did" property="id"/>
                <result column="dname" property="name"/>
    
            </association>
    
        </resultMap>
    
    </mapper>

连接数据库配置，mybatis主配置和自定义获取SQLSession对象的工具类省略，详细请看mybatis学习笔记01  
测试：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70]测试结果：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70 1]

[2018121323434662.png]: /images/20220405/f99baa8f080d463795bf511078b76d73.png
[20181213233403482.png]: https://img-blog.csdnimg.cn/20181213233403482.png
[20181213233430280.png]: /images/20220405/474c7516c07f4acba57ef99978d640bc.png
[20181213233512359.png]: /images/20220405/39ee7b697b9e4a3797012a255bc4d3dd.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70]: /images/20220405/d4159594c4f2420a9b3321fe1e4e7ca5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70 1]: /images/20220405/38902024fb5f4bf5aa4aef7cce299662.png