MyBatis - 一对多对象关联查询

作者：fyupeng
技术专栏：☞ https://github.com/fyupeng
项目地址：☞ https://github.com/fyupeng/distributed-blog-system-api

留给读者

一、介绍

比如你需要在Company对象中，嵌套列表SonCompanys和ContactInfos，而且还是直接通过数据库查询出来，不想自己遍历去构造这种对象，那么你可以使用MyBatis的collection 关键字。

二、代码

<select id="queryCompanyDataByKey" resultMap="CompanyItemMap">
        select * from (
        	select a.id, a.area, a.uniscid, a.updatetime as updateTime, b.area as sonArea, b.uniscid as sonUniscid, c.name as contactName
        	from company a inner join son_comopany b on a.sonId = b.id
        	inner join contact_info c on a.contact_id = c.id
       	)
</select>

<resultMap id="CompanyItemMap" type="com.fyupeng.company">
        <id property="id" column="id" />
        <result property="area" column="area" />
        <result property="uniscid" column="uniscid" />
        // 子公司
        <result property="updateTime" column="updateTime" />
        <collection property="sonCompanys" ofType="com.fyupeng.SonCompany">
	        <result property="sonArea" column="sonArea" />
	        <result property="sonUniscid" column="sonUniscid" />
        </collection>
        // 联系人信息
        <collection property="contactInfos" ofType="com.fyupeng.ContactInfo">
            <result property="contactName" column="contactName" />
        </collection>
    </resultMap>

三、总结

简洁、高效、实用！