Mybatis-Plus框架中使用IPage进行一对多分页的bug及修复

场景

做一个刷题app，需要分页显示所有题目。每个题目有多个选项。分页时原希望每页10题，带上所有选项，现在却变成只有几个题目，而他们的选项数之和为10。

修复

xml配置中，将对多部分的映射加上select属性，单写方法进行查询。

同时，原查询方法中加入DISTINCT限定。

若使用ORDER排序，则SELECT中还需加上排序字段。

代码

question.xml

    
        
        
        
    
    
        
        
        
        
        
    
    
        SELECT DISTINCT
            q.question_id, q.create_time, q.question_type, q.question_content, q.update_time
        FROM
            t_question q
        LEFT JOIN
            t_question_key k
        ON q.question_id = k.question_id
        
            
                q.teacher_id = #{teacherId}
            
            
                AND q.question_type = #{type}
            
            
                AND LOCATE(#{keyWord}, q.question_content)
            
        
        ORDER BY q.update_time DESC
    

    
        SELECT
               k.key_id, k.answer_content, k.correct
        FROM
             t_question_key k
        WHERE
              k.question_id = #{question_id}
    

QuestionRepository.java

@Mapper
@Repository
public interface QuestionRepository extends BaseMapper {

    IPage selectAllWithKey(
            IPage page,
            @Param("keyWord") String keyWord,
            @Param("type") Short type,
            @Param("teacherId") Long teacherId);

}

QuestionWithKey.java

@Data
@With
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class QuestionWithKey implements Serializable {
    
    private static final long serialVersionUID = 4192873408617718827L;
    
    private Long id;

    private Short type;

    private String content;

    private Date date;

    private List keys;

}

KeyPO.java

@Data
@With
@Builder
@NoArgsConstructor
@AllArgsConstructor
@TableName("t_question_key")
public class KeyPO implements Serializable {

    private static final long serialVersionUID = 9117947918115257855L;

    @TableField("question_id")
    private Long questionId;

    @TableField("key_id")
    private Short keyId;

    @TableField(fill = FieldFill.INSERT)
    private Date createTime;

    @TableField(fill = FieldFill.INSERT_UPDATE)
    private Date updateTime;

    @TableField("answer_content")
    private String content;

    @TableField
    private Boolean correct;
}