public class Question implements Serializable {
   
    private int id;                 //問題Id
    private int accountId;     //用戶id
    private String content;    //問題
    private Date createTime;
    private String createBy;
    private Date updateTime;
    private String updateBy;
    private int status;        //
 
問題狀態  0：邏輯刪除，1：未回答，2：已回答
　  private List<Answer> answers;  //註意這個屬性
}        

public class Answer implements Serializable{
    
    private int id;    //答案Id
    private int questionId;    //問題Id 
    private int managerId;   //回復者Id(默認管理員)
    private String content;   //回復內容
    private Date createTime; //
 
回復時間
    private String createBy;
    private Date updateTime;
    private String updateBy;
    private int status;

}    

mybatis中的查詢語句

<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" >  <!-- 註意ID的對應 -->
        <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類中的屬性， column指數據庫中的字段名-->
            <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>

正確返回。

<resultMap>中 <collection>的使用