一、课程列表后端接口

1、课程列表

（1）课程列表vo类

@ApiModel(value = "课程查询对象", description = "课程查询对象封装")
@Data
public class CourseQueryVo implements Serializable {
    private static final long serialVersionUID = 1L;
    @ApiModelProperty(value = "课程名称")
    private String title;
    @ApiModelProperty(value = "讲师id")
    private String teacherId;
    @ApiModelProperty(value = "一级类别id")
    private String subjectParentId;
    @ApiModelProperty(value = "二级类别id")
    private String subjectId;
    @ApiModelProperty(value = "销量排序")
    private String buyCountSort;
    @ApiModelProperty(value = "最新时间排序")
    private String gmtCreateSort;
    @ApiModelProperty(value = "价格排序")
    private String priceSort;
}

（2）课程列表controller

@ApiOperation(value = "分页课程列表")
@PostMapping(value = "{page}/{limit}")
public R pageList(
        @ApiParam(name = "page", value = "当前页码", required = true)
        @PathVariable Long page,
        @ApiParam(name = "limit", value = "每页记录数", required = true)
        @PathVariable Long limit,
        @ApiParam(name = "courseQuery", value = "查询对象", required = false)
                @RequestBody(required = false) CourseQueryVo courseQuery){
    Page<EduCourse> pageParam = new Page<EduCourse>(page, limit);
    Map<String, Object> map = courseService.pageListWeb(pageParam, courseQuery);
    return  R.ok().data(map);
}

（3）课程列表service

@Override
public Map<String, Object> pageListWeb(Page<EduCourse> pageParam, CourseQueryVo courseQuery) {
        QueryWrapper<EduCourse> queryWrapper = new QueryWrapper<>();
        if (!StringUtils.isEmpty(courseQuery.getSubjectParentId())) {
            queryWrapper.eq("subject_parent_id", courseQuery.getSubjectParentId());
        }
        if (!StringUtils.isEmpty(courseQuery.getSubjectId())) {
            queryWrapper.eq("subject_id", courseQuery.getSubjectId());
        }
        if (!StringUtils.isEmpty(courseQuery.getBuyCountSort())) {
            queryWrapper.orderByDesc("buy_count");
        }
        if (!StringUtils.isEmpty(courseQuery.getGmtCreateSort())) {
            queryWrapper.orderByDesc("gmt_create");
        }
        if (!StringUtils.isEmpty(courseQuery.getPriceSort())) {
            queryWrapper.orderByDesc("price");
        }
        baseMapper.selectPage(pageParam, queryWrapper);
        List<EduCourse> records = pageParam.getRecords();
        long current = pageParam.getCurrent();
        long pages = pageParam.getPages();
        long size = pageParam.getSize();
        long total = pageParam.getTotal();
        boolean hasNext = pageParam.hasNext();
        boolean hasPrevious = pageParam.hasPrevious();
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("items", records);
        map.put("current", current);
        map.put("pages", pages);
        map.put("size", size);
        map.put("total", total);
        map.put("hasNext", hasNext);
        map.put("hasPrevious", hasPrevious);
        return map;
}

二、课程详情页

1、vo对象的定义

在项目中很多时候需要把model转换成dto用于网站信息的展示，按前端的需要传递对象的数据，保证model对外是隐私的，例如密码之类的属性能很好地避免暴露在外，同时也会减小数据传输的体积。
CourseWebVo.java

package com.guli.edu.vo;
@ApiModel(value="课程信息", description="网站课程详情页需要的相关字段")
@Data
public class CourseWebVo implements Serializable {
    private static final long serialVersionUID = 1L;
    private String id;
    @ApiModelProperty(value = "课程标题")
    private String title;
    @ApiModelProperty(value = "课程销售价格，设置为0则可免费观看")
    private BigDecimal price;
    @ApiModelProperty(value = "总课时")
    private Integer lessonNum;
    @ApiModelProperty(value = "课程封面图片路径")
    private String cover;
    @ApiModelProperty(value = "销售数量")
    private Long buyCount;
    @ApiModelProperty(value = "浏览数量")
    private Long viewCount;
    @ApiModelProperty(value = "课程简介")
    private String description;
    @ApiModelProperty(value = "讲师ID")
    private String teacherId;
    @ApiModelProperty(value = "讲师姓名")
    private String teacherName;
    @ApiModelProperty(value = "讲师资历,一句话说明讲师")
    private String intro;
    @ApiModelProperty(value = "讲师头像")
    private String avatar;
    @ApiModelProperty(value = "课程类别ID")
    private String subjectLevelOneId;
    @ApiModelProperty(value = "类别名称")
    private String subjectLevelOne;
    @ApiModelProperty(value = "课程类别ID")
    private String subjectLevelTwoId;
    @ApiModelProperty(value = "类别名称")
    private String subjectLevelTwo;
}

2、课程和讲师信息的获取

1）Mapper中关联查询课程和讲师信息

CourseMapper.java

CourseWebVo selectInfoWebById(String courseId);

CourseMapper.xml

<select id="selectInfoWebById" resultType="com.guli.edu.vo.CourseWebVo">
  SELECT
    c.id,
    c.title,
    c.cover,
    CONVERT(c.price, DECIMAL(8,2)) AS price,
    c.lesson_num AS lessonNum,
    c.cover,
    c.buy_count AS buyCount,
    c.view_count AS viewCount,
    cd.description,
    t.id AS teacherId,
    t.name AS teacherName,
    t.intro,
    t.avatar,
    s1.id AS subjectLevelOneId,
    s1.title AS subjectLevelOne,
    s2.id AS subjectLevelTwoId,
    s2.title AS subjectLevelTwo
  FROM
    edu_course c
    LEFT JOIN edu_course_description cd ON c.id = cd.id
    LEFT JOIN edu_teacher t ON c.teacher_id = t.id
    LEFT JOIN edu_subject s1 ON c.subject_parent_id = s1.id
    LEFT JOIN edu_subject s2 ON c.subject_id = s2.id
  WHERE
    c.id = #{id}
</select>

2）业务层获取数据并更新浏览量

CourseService
接口

/**
     * 获取课程信息
     * @param id
     * @return
     */
CourseWebVo selectInfoWebById(String id);
/**
     * 更新课程浏览数
     * @param id
     */
void updatePageViewCount(String id);

实现

@Override
public CourseWebVo selectInfoWebById(String id) {
    this.updatePageViewCount(id);
    return baseMapper.selectInfoWebById(id);
}
@Override
public void updatePageViewCount(String id) {
    Course course = baseMapper.selectById(id);
    course.setViewCount(course.getViewCount() + 1);
    baseMapper.updateById(course);
}

3）接口层

CourseController

@Autowired
private ChapterService chapterService;
@ApiOperation(value = "根据ID查询课程")
@GetMapping(value = "{courseId}")
public R getById(
    @ApiParam(name = "courseId", value = "课程ID", required = true)
    @PathVariable String courseId){
    //查询课程信息和讲师信息
    CourseWebVo courseWebVo = courseService.selectInfoWebById(courseId);
    //查询当前课程的章节信息
    List<ChapterVo> chapterVoList = chapterService.nestedList(courseId);
    return R.ok().data("course", courseWebVo).data("chapterVoList", chapterVoList);
}