mybatis中映射一对多关系

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一对多

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其中columnPrefix是给字段加前缀，在查出的数据id重命名为express_id加上前缀即可

<resultMap id="getDetailsResultMap" type="StudentArchivesInfoExpressDetailsDTO">
    <id column="id" property="id">id>
    <result column="student_id" property="studentId">result>
    <collection property="express" columnPrefix="express_" ofType="ExpressDTO">
        <id column="id" property="id">id>
        <result column="content" property="content">result>
        <result column="time" property="time">result>
    collection>
resultMap>

<select id="getDetails" resultMap="getDetailsResultMap">
    SELECT
        a.id,
        a.student_id,
        b.id AS express_id,
        b."content" AS express_content,
        b."time" AS express_time
    FROM
        t_student_archives_info_express AS a 
        LEFT JOIN t_express_message AS b
        ON a.id = b.relation_id AND b.relation_type = 1
select>

//实体类
public class StudentArchivesInfoExpressDetailsDTO{
	private Long id;
	private Long studentId;
	private List<ExpressDTO> express;
}