Mybatis（五）：一对多级联查询

主要是使用<collection>来实现关联。

xml代码

<resultMap id="userWithOrderMap" type="cn.saytime.domain.User">
        <id property="id" column="uid" javaType="java.lang.Long"></id>
        <result property="username" column="username" javaType="java.lang.String"></result>
        <result property="age" column="age" javaType="java.lang.Integer"></result>
        <collection property="orderList" javaType="java.util.List" ofType="cn.saytime.domain.Order">
            <id property="id" column="oid" javaType="java.lang.Long"></id>
            <result property="order_no" column="order_no" javaType="java.lang.String"></result>
            <result property="price" column="price" javaType="java.math.BigDecimal"></result>
        </collection>
    </resultMap>

    <select id="selectByIdWithOrder" parameterType="java.lang.Long" resultMap="userWithOrderMap">
        SELECT u.id AS uid, u.username, u.age, o.id AS oid, o.order_no, o.price
        FROM tb_user u
        JOIN tb_order o ON u.id = o.uid
        WHERE u.id = #{id}
    </select>

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