1.封装实体类封装数据库查询的课程信息

@Data
public class CoursePublishVo {

    private String title;
    private String cover;
    private Integer lessonNum;
    private String subjectLevelOne;
    private String subjectLevelTwo;
    private String teacherName;
    private String price;//只用于显示

}

2.编写接口

CoursePublishVo getPublishInfo(String id);

3.编写mapper文件

    <select id="getCoursePublishInfo" resultType="com.wang.eduservice.entity.vo.CoursePublishVo">
        select
       ec.id,
       ec.title,
       ec.price,
       ec.lesson_num as lessonNum,
       ec.cover,
       et.name as teacherName,
       es1.title as subjectLevelOne,
       es2.title as subjectLevelTwo
from edu_course ec
  left join edu_course_description ecd on ec.id=ecd.id
  left join  edu_teacher et on ec.teacher_id =et.id
  left join edu_subject es1 on  ec.subject_parent_id=es1.id
  left join edu_subject es2 on ec.subject_id=es2.id
where ec.id=#{courseId}


    </select>

4.调用接口方法

 @Override
    public CoursePublishVo getPublishInfo(String id) {
        CoursePublishVo coursePublishInfo = baseMapper.getCoursePublishInfo(id);


        return coursePublishInfo;
    }

 5.controller调用

@GetMapping("getCoursePublishVo/{id}")
    public R getCoursePublishVo(@PathVariable String id) {
        CoursePublishVo coursePublishVo = eduCourseService.getPublishInfo(id);


        return R.ok().data("publishCourse", coursePublishVo);

    }