<resultMap>中 <collection>的使用

public class Question implements Serializable {

    private int id;                 //问题Id
    private int accountId;     //用户id
    private String content;    //问题
    private Date createTime;
    private String createBy;
    private Date updateTime;
    private String updateBy;
    private int status;        //问题状态  0：逻辑删除，1：未回答，2：已回答
　  private List<Answer> answers;  //注意这个属性
}        

public class Answer implements Serializable{

    private int id;    //答案Id
    private int questionId;    //问题Id
    private int managerId;   //回复者Id(默认管理员)
    private String content;   //回复内容
    private Date createTime; //回复时间
    private String createBy;
    private Date updateTime;
    private String updateBy;
    private int status;

}    

mybatis中的查询语句

<select id="showAnswers" resultMap="linkedResultMap"  parameterType="int">
        SELECT
            a.id,a.`questionId`,a.`content` AS answer,a.`createTime` as aCreateTime,a.`managerId`,
            q.id,q.`accountId`,q.`content` AS question,q.`status`,q.`createTime` as qCreateTime
        FROM
            answers AS a
        LEFT JOIN
            questions AS q
        ON
            q.`id` = a.`questionId`
        WHERE
            q.`status` = 2
        AND
            q.`accountId`=#{acconutId} ;
    </select>

    <resultMap type="entity.Question" id="linkedResultMap" >  <!-- 注意ID的对应 -->
        <id property="id" column="id"/>
        <result property="accountId" column="accountId"/>
        <result property="content" column="question"/>
        <result property="status" column="status"/>
        <result property="createTime" column="qCreateTime"/>
        <collection property="answers" ofType="entity.Answer">
        <!-- property指 Answer类中的属性， column指数据库中的字段名-->
            <id property="id" column="id"/>
            <result property="questionId" column="questionId"/>
            <result property="managerId" column="managerId"/>
            <result property="content" column="answer"/>
            <result property="createTime" column="aCreateTime"/>
        </collection>
    </resultMap>

正确返回。