mybatis一对多嵌套结果 mybatis学习笔记07

ゝ一纸荒年。 2022-04-04 04:59 376阅读 0赞

mybatis一对多嵌套结果：  
一对多嵌套结果的特点：只发送一条sql语句  
![在这里插入图片描述][20181214235759465.png]  
步骤：  
新建domain类：  
![在这里插入图片描述][2018121423404738.png]![在这里插入图片描述][20181214234132118.png]数据库设计：  
![在这里插入图片描述][20181214234258962.png]  
![在这里插入图片描述][20181214234235268.png]新建domainMapper接口：在本例中为DepartmentMapper  
![在这里插入图片描述][20181214234358226.png]新建domainMapper.xml在本例中为：DepartmentMapper.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.onetomany02.DepartmentMapper">
        
        <select id="findAll" resultMap="DepartmentMap">
            select d.id,d.name,e.id eid,e.username eusername,e.age eage,e.dept_id from department d left join employee e on d.id=e.dept_id
        </select>
        
        <resultMap id="DepartmentMap" type="cn.itsource.mybatis.onetomany02.Department">
    
            <id column="id" property="id"/>
            <result column="name" property="name"/>
    	
            <collection property="list"
                        javaType="list"
                        ofType="cn.itsource.mybatis.onetomany02.Employee"
                        >
                <id column="eid" property="id"/>
                <result column="eusername" property="username"/>
                <result column="eage" property="age"/>
    
            </collection>
    
        </resultMap>
    
    
    </mapper>

在DepartmentMapper.xml中的注意事项：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70]在mybatis的主配置文件中引入我们定义的DepartmentMapper.xml文件的路径：  
![在这里插入图片描述][20181214235232288.png]  
连接数据库的配置和mybatis主配置文件和自定义mybatis工具类步骤省略，详细步骤查看 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 1]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 2]

[20181214235759465.png]: /images/20220404/b0f5961b39794be390af4563c573751b.png
[2018121423404738.png]: https://img-blog.csdnimg.cn/2018121423404738.png
[20181214234132118.png]: /images/20220404/21f9c48c145448edb548585c0f309740.png
[20181214234258962.png]: /images/20220404/bda89087963940c183b308506b8e077d.png
[20181214234235268.png]: /images/20220404/dc4c78ddac27430cb36a6dc7990c7efc.png
[20181214234358226.png]: /images/20220404/48f8c107ed0741a284009714ebefb30d.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70]: /images/20220404/0242ba8abdfb4048bebb9795760af2d9.png
[20181214235232288.png]: /images/20220404/25e45e8a618b4d94980c6d27ccbb9f12.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70 1]: /images/20220404/2c0200a59a7c46cab08b6151bfea47b9.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3N1cHJlemhlbmc_size_16_color_FFFFFF_t_70 2]: /images/20220404/f2ace33596ad4c0b8e345e7206edc599.png