Mybatis 多表间查询之 一对多

前期准备见 Mybatis 多表间查询之 多对一

0.准备

1. domain Category

2. 主配置文件

...
 </environments>
    <mappers>
        <mapper resource="cn/ccut/mapper/CategoryDao.xml"  ></mapper>
    </mappers>
</configuration>

3. 接口ICategoryDao

public interface ICategoryDao {
    Category getCate(String cid);
}

1. 连接查询

1.1 映射配置文件 CategoryDao.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.ccut.dao.ICategoryDao">

    <resultMap id="res1" type="cn.ccut.domain.Category">
        <id property="cid" column="tcid"/>
        <result property="cname" column="tcname"/>
        <result property="desc" column="desc"/>

        <collection property="bList" ofType="cn.ccut.domain.Book">
            <id property="bid" column="bid"/>
            <result property="bname" column="bname"/>
            <result property="author" column="author"/>
            <result property="price" column="price"/>
            <result property="press" column="press"/>
            <result property="cid" column="cid"/>
        </collection>
        
    </resultMap>
    
    <select id="getCate" resultMap="res1">
select t1.cid tcid,t1.cname tcname,t1.desc,t.* from t_book  t join t_category t1 on t.cid=t1.cid and t.cid=#{cid}
    </select>
</mapper>

1.2 测试

public class tests {
    @Test
    public void fun(){
        ICategoryDao mapper = MyBatisUtil.openSession().getMapper(ICategoryDao.class);
        System.out.println( mapper.getCate("5F79D0D246AD4216AC04E9C5FAB3199E"));
    }
}

成功

2. 分步查询

2.1 CategoryDao.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.ccut.dao.ICategoryDao">

    <resultMap id="res1" type="cn.ccut.domain.Category">
        <id property="cid" column="cid"/>
        <collection property="bList" column="cid" ofType="cn.ccut.domain.Book"  select="selectBook">
        </collection>
    </resultMap>

    <select id="getCate" resultMap="res1">
select * from t_Category where cid=#{cid}
    </select>
    
    <select id="selectBook" resultType="cn.ccut.domain.Book">
        select * from t_book where cid=#{c1id}
    </select>
</mapper>