1、MyBatisPlusConfig中配置分页插件

依赖参考：https://www.cnblogs.com/konglxblog/p/16793936.html

package com.stu.service.base.config;

import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.autoconfigure.ConfigurationCustomizer;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

/**
 * 分页功能
 */
@Configuration
@MapperScan("com.stu.service.*.mapper")
public class MyBatisPlusConfig {

    /**
     * 新的分页插件,一缓和二缓遵循mybatis的规则,需要设置 MybatisConfiguration#useDeprecatedExecutor = false 避免缓存出现问题(该属性会在旧插件移除后一同移除)
     */
    @Bean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
        return interceptor;
    }


}

2、方式一（不涉及mapper.java文件和sql.xml文件）

controller

package com.stu.service.edu.controller.admin;


import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.stu.service.base.result.R;
import com.stu.service.edu.entity.Teacher;
import com.stu.service.edu.entity.vo.ChapterVo;
import com.stu.service.edu.entity.vo.TeacherQueryVo;
import com.stu.service.edu.service.TeacherService;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * <p>
 * 讲师 前端控制器
 * </p>
 *
 * @author stu
 * @since 2022-04-11
 */
@RestController
@RequestMapping("/admin/edu/teacher")
//@CrossOrigin
public class TeacherController {

    @Autowired
    private TeacherService teacherService;

    /***********************************
     * 用途说明:批量删除
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @DeleteMapping("batchRemoveTeacher")
    public R batchRemoveTeacher(@RequestBody List<String> idList) {

        boolean result = teacherService.removeByIds(idList);
        if (result) {
            return R.ok().message("删除成功");
        }
        return R.error().message("删除失败");
    }

    /***********************************
     * 用途说明:删除讲师
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @DeleteMapping("deleteTeacher/{id}")
    public R deleteTeacher(@PathVariable String id) {

        /*        if (true) {
            throw new CustomException(ResultCodeEnum.DIVIDE_ZERO);
        }*/

        boolean result = teacherService.removeById(id);
        if (result) {
            return R.ok().message("删除成功");
        }
        return R.error().message("删除失败");
    }

    /***********************************
     * 用途说明:修改讲师
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @PostMapping("updateTeacher")
    public R updateTeacher(@RequestBody Teacher teacher) {
        boolean result = teacherService.updateById(teacher);
        if (result) {
            return R.ok().message("更新成功");
        }
        return R.error().message("更新失败");
    }

    /***********************************
     * 用途说明:添加讲师
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @ApiOperation("添加讲师")
    @PostMapping("addTeacher")
    public R addTeacher(@ApiParam("讲师对象") @RequestBody Teacher teacher) {
        boolean result = teacherService.save(teacher);
        if (result) {
            return R.ok().message("保存成功");
        }
        return R.error().message("保存失败");
    }

    /***********************************
     * 用途说明:查询讲师表所有数据
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @GetMapping("findAll")
    public R findAllTeacher() {
        List<Teacher> list = teacherService.list();
        return R.ok().data("list", list);
    }

    /***********************************
     * 用途说明:查询
     * 返回值说明: com.stu.service.edu.entity.Teacher
     ***********************************/
    @GetMapping("get/{id}")
    public R getTeacher(@PathVariable String id) {

        return R.ok().data("dataInfo", teacherService.getById(id));

    }

    /***********************************
     * 用途说明:查询讲师表所有数据
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @GetMapping("pageList/{page}/{limit}")
    public R pageList(@PathVariable long page, @PathVariable long limit, TeacherQueryVo teacherQueryVo) {
        Page<Teacher> pageParam = new Page<>(page, limit);
        teacherService.listPage(pageParam, teacherQueryVo);
        Map<String, Object> map = new HashMap<String, Object>();
        long total = pageParam.getTotal();
        List<Teacher> list = pageParam.getRecords();
        map.put("total", total);
        map.put("list", list);
        return R.ok().data(map);

    }
}

service接口

package com.stu.service.edu.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.stu.service.edu.entity.Teacher;
import com.baomidou.mybatisplus.extension.service.IService;
import com.stu.service.edu.entity.vo.ChapterVo;
import com.stu.service.edu.entity.vo.TeacherQueryVo;

import java.util.List;
import java.util.Map;

/**
 * <p>
 * 讲师 服务类
 * </p>
 *
 * @author stu
 * @sinc e 2022-04-11
 */
public interface TeacherService extends IService<Teacher> {

    /***********************************
     * 用途说明:分页
     * @param pageParam
     * @param teacherQueryVo
     * 返回值说明:
     * @return com.baomidou.mybatisplus.core.metadata.IPage<com.stu.service.edu.entity.Teacher>
     ***********************************/
    IPage<Teacher> listPage(Page<Teacher> pageParam, TeacherQueryVo teacherQueryVo);

    /***********************************
     * 用途说明:取得推荐讲师
     * 返回值说明:
     * @return java.util.List<com.stu.service.edu.entity.Teacher>
     ***********************************/
    List<Teacher> listHotTeacher();

    /***********************************
     * 用途说明:前台讲师分页
     * @param pageParam
     * 返回值说明:
     * @return java.util.Map<java.lang.String, java.lang.Object>
     ***********************************/
    Map<String,Object> listPageTeachers(Page<Teacher> pageParam);

}

service实现类

package com.stu.service.edu.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.stu.service.edu.entity.Teacher;
import com.stu.service.edu.entity.vo.TeacherQueryVo;
import com.stu.service.edu.mapper.TeacherMapper;
import com.stu.service.edu.service.TeacherService;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * <p>
 * 讲师 服务实现类
 * </p>
 *
 * @author stu
 * @since 2022-04-11
 */
@Service
public class TeacherServiceImpl extends ServiceImpl<TeacherMapper, Teacher> implements TeacherService {

    @Autowired
    private TeacherService teacherService;

    /***********************************
     * 用途说明:分页
     * @param pageParam
     * @param teacherQueryVo
     * 返回值说明:
     * @return com.baomidou.mybatisplus.core.metadata.IPage<com.stu.service.edu.entity.Teacher>
     ***********************************/
    @Override
    public IPage<Teacher> listPage(Page<Teacher> pageParam, TeacherQueryVo teacherQueryVo) {

        QueryWrapper<Teacher> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByAsc("sort", "id");

        if (teacherQueryVo == null) {
            return baseMapper.selectPage(pageParam, queryWrapper);
        }

        String name = teacherQueryVo.getName();
        Integer level = teacherQueryVo.getLevel();
        String begin = teacherQueryVo.getBegin();
        String end = teacherQueryVo.getEnd();

        if (!StringUtils.isEmpty(name)) {
            queryWrapper.like("name", name);
        }

        if (null != level) {
            queryWrapper.eq("level", level);
        }

        if (!StringUtils.isEmpty(begin)) {
            queryWrapper.ge("gmt_create", begin);
        }

        if (!StringUtils.isEmpty(end)) {
            queryWrapper.le("gmt_create", end);
        }

        return baseMapper.selectPage(pageParam, queryWrapper);
    }

    /***********************************
     * 用途说明:取得推荐讲师
     * 返回值说明:
     * @return java.util.List<com.stu.service.edu.entity.Teacher>
     ***********************************/
    @Cacheable(value = "index", key = "'listHotTeacher'")
    @Override
    public List<Teacher> listHotTeacher() {
        QueryWrapper<Teacher> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("sort");
        queryWrapper = queryWrapper.last("limit 4");
        return baseMapper.selectList(queryWrapper);
    }

    @Override
    public Map<String, Object> listPageTeachers(Page<Teacher> pageParam) {
        QueryWrapper<Teacher> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("gmt_modified").orderByDesc("sort");
        baseMapper.selectPage(pageParam,queryWrapper);

        Map<String, Object> mapParam = new HashMap<>();
        mapParam.put("items", pageParam.getRecords());//当前页记录
        mapParam.put("current", pageParam.getCurrent());//当前页
        mapParam.put("pages", pageParam.getPages());//共有多少页
        mapParam.put("size", pageParam.getSize());//每页的记录数
        mapParam.put("total", pageParam.getTotal());//总记录数
        mapParam.put("hasNext", pageParam.hasNext());//是否有上一页
        mapParam.put("hasPrevious", pageParam.hasPrevious());//是否有下一页

        return mapParam;
    }
}

3、方式二，复杂查询需要用到sql，涉及mapper文件和xml文件

controller

package com.stu.service.edu.controller.admin;


import com.baomidou.mybatisplus.core.metadata.IPage;
import com.stu.service.base.result.R;
import com.stu.service.base.result.ResultCodeEnum;
import com.stu.service.edu.entity.Course;
import com.stu.service.edu.entity.CourseDescription;
import com.stu.service.edu.entity.form.CourseInfoForm;
import com.stu.service.edu.entity.vo.CoursePublishVo;
import com.stu.service.edu.entity.vo.CourseQueryVo;
import com.stu.service.edu.entity.vo.CourseVo;
import com.stu.service.edu.service.CourseService;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

/**
 * <p>
 * 课程 前端控制器
 * </p>
 *
 * @author stu
 * @since 2022-05-05
 */
@RestController
@RequestMapping("/admin/edu/course")
//@CrossOrigin
public class CourseController {

    @Autowired
    private CourseService courseService;

    /***********************************
     * 用途说明:更新课程基本信息和课程简介
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @PostMapping("updateCourseForm")
    private R updateCourseForm(@RequestBody CourseInfoForm courseInfoForm) {

        //非空判断
        if (null == courseInfoForm || StringUtils.isEmpty(courseInfoForm.getId())) {
            return R.error().message(ResultCodeEnum.PARAM_ERROR.getMessage());
        }
        //更新课程进步信息和课程简介
        boolean updateCourseForm = courseService.updateCourseForm(courseInfoForm);
        if (updateCourseForm) {
            return R.ok();
        } else {
            return R.error().message(ResultCodeEnum.UPDATE_ERROR.getMessage());
        }

    }

    /***********************************
     * 用途说明:保存课程基本信息和课程简介
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @PostMapping("saveCourseInfo")
    private R saveCourseInfo(@RequestBody CourseInfoForm courseInfoForm) {
        return R.ok().data("data", courseService.saveCourseInfo(courseInfoForm));
    }

    /***********************************
     * 用途说明:取得课程的基本信息和课程简介
     * 返回值说明: com.stu.service.base.result.R
     ***********************************/
    @GetMapping("getCourseForm/{courseId}")
    private R getCourseForm(@PathVariable(required = true) String courseId) {

        if (StringUtils.isEmpty(courseId)) {
            return R.error().message(ResultCodeEnum.PARAM_ERROR.getMessage());
        }
        CourseInfoForm courseInfoForm = courseService.getCourseForm(courseId);
        if (null == courseInfoForm) {
            return R.error().message(ResultCodeEnum.DATA_NULL.getMessage());
        } else {
            return R.ok().data("data", courseService.getCourseForm(courseId));
        }

    }

    /***********************************
     * 用途说明:去看发布课程的详情
     * @param courseId
     * 返回值说明:
     * @return com.stu.service.base.result.R
     ***********************************/
    @GetMapping("getPublishCourseByid/{courseId}")
    public R getPublishCourseByid(@PathVariable String courseId) {
        CoursePublishVo coursePublish = courseService.getCoursePublishById(courseId);
        if(null != coursePublish){
            return R.ok().data("data",coursePublish);
        }
        return R.error().message(ResultCodeEnum.DATA_NULL.getMessage());
    }

    /***********************************
     * 用途说明:发布课程
     * @param courseId
     * 返回值说明:
     * @return com.stu.service.base.result.R
     ***********************************/
    @GetMapping("publishCourse/{courseId}")
    public R publishCourse(@PathVariable String courseId) {
        boolean result = courseService.publishCourse(courseId);
        if (result) {
            return R.ok();
        }
        return R.error().message(ResultCodeEnum.UPDATE_ERROR.getMessage());
    }

    /***********************************
     * 用途说明:分页
     * @param page
     * @param limit
     * @param courseQueryVo
     * 返回值说明:
     * @return com.stu.service.base.result.R
     ***********************************/
    @GetMapping("pageCourses/{page}/{limit}")
    public R pageCourses(@PathVariable Long page, @PathVariable Long limit, CourseQueryVo courseQueryVo) {
        IPage<CourseVo> coursePublishVoIPage = courseService.pageCourses(page, limit, courseQueryVo);

        return R.ok().data("data",coursePublishVoIPage);

    }

    /***********************************
     * 用途说明:根據id刪除課程（包括课时，小节，详情等）
     * @param id
     * 返回值说明:
     * @return com.stu.service.base.result.R
     ***********************************/
    @DeleteMapping("deleteById/{id}")
    public R deleteById(@PathVariable String id) {
        boolean result = courseService.deleteById(id);
        if (result) {
            return R.ok();
        }
        return R.error().message(ResultCodeEnum.UPDATE_ERROR.getMessage());
    }



}

service接口

package com.stu.service.edu.service;

import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.stu.service.base.dto.CourseDto;
import com.stu.service.edu.entity.Course;
import com.baomidou.mybatisplus.extension.service.IService;
import com.stu.service.edu.entity.form.CourseInfoForm;
import com.stu.service.edu.entity.vo.*;

import java.util.List;
import java.util.Map;

/**
 * <p>
 * 课程 服务类
 * </p>
 *
 * @author stu
 * @since 2022-05-05
 */
public interface CourseService extends IService<Course> {

    /***********************************
     * 用途说明:保存课程基本信息和课程简介
     * 返回值说明: com.stu.service.edu.entity.Course
     ***********************************/
    Course saveCourseInfo(CourseInfoForm courseInfoForm);

    /***********************************
     * 用途说明:取得课程的基本信息和课程简介
     * 返回值说明: com.stu.service.edu.entity.form.CourseInfoForm
     ***********************************/
    CourseInfoForm getCourseForm(String id);

    /***********************************
     * 用途说明:更新课程基本信息和课程简介
     * 返回值说明: boolean
     ***********************************/
    boolean updateCourseForm(CourseInfoForm courseInfoForm);

    /***********************************
     * 用途说明:查询课程发布信息
     * @param courseId
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.CoursePublishVo
     ***********************************/
    CoursePublishVo getCoursePublishById(String courseId);

    /***********************************
     * 用途说明:发布课程
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    boolean publishCourse(String id);

    /***********************************
     * 用途说明:分页
     * @param page
     * @param limit
     * @param courseQueryVo
     * 返回值说明:
     * @return com.baomidou.mybatisplus.core.metadata.IPage<com.stu.service.edu.entity.vo.CoursePublishVo>
     ***********************************/
    IPage<CourseVo> pageCourses(Long page, Long limit, CourseQueryVo courseQueryVo);


    /***********************************
     * 用途说明:根据课程id删除课程（章节，详情，视频都需要删除）
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
   boolean deleteById(String id);

   /***********************************
    * 用途说明:取得热门课程
    * 返回值说明:
    * @return java.util.List<com.stu.service.edu.entity.Course>
    ***********************************/
   List<Course> listHotCourses();

   /***********************************
    * 用途说明:根据讲师id查询所有课程
    * @param id
    * 返回值说明:
    * @return java.util.List<com.stu.service.edu.entity.Course>
    ***********************************/
   List<Course> listCourseByTeacherId(String id);

    /***********************************
     * 用途说明:前端课程分页nuxt
     * @param pageParam
     * @param courseQueryVo
     * 返回值说明:
     * @return java.util.Map<java.lang.String, java.lang.Object>
     ***********************************/
    Map<String,Object> listPageCourses(Page<Course> pageParam, CourseQueryVo courseQueryVo);

    /***********************************
     * 用途说明:根据课程id查询详情nuxt
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.ApiCourseVo
     ***********************************/
    ApiCourseVo getApiCourseById(String id);

    /***********************************
     * 用途说明:更新游览数
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    boolean updateViewCount(String id);

    /***********************************
     * 用途说明:根据课程id查询订单相关的课程信息
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.CourseApiVo
     ***********************************/
    CourseDto getCourseById(String id);

    /***********************************
     * 用途说明:更新課程銷售量
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    boolean  updateBuyCountById(String id);
}

service实现类

package com.stu.service.edu.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.stu.service.base.dto.CourseDto;
import com.stu.service.base.exception.CustomException;
import com.stu.service.base.result.ResultCodeEnum;
import com.stu.service.edu.entity.Chapter;
import com.stu.service.edu.entity.Course;
import com.stu.service.edu.entity.CourseDescription;
import com.stu.service.edu.entity.constant.CourseConstant;
import com.stu.service.edu.entity.form.CourseInfoForm;
import com.stu.service.edu.entity.vo.ApiCourseVo;
import com.stu.service.edu.entity.vo.CoursePublishVo;
import com.stu.service.edu.entity.vo.CourseQueryVo;
import com.stu.service.edu.entity.vo.CourseVo;
import com.stu.service.edu.mapper.CourseMapper;
import com.stu.service.edu.service.ChapterService;
import com.stu.service.edu.service.CourseDescriptionService;
import com.stu.service.edu.service.CourseService;
import com.stu.service.edu.service.VideoService;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cache.annotation.Cacheable;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * <p>
 * 课程 服务实现类
 * </p>
 *
 * @author stu
 * @since 2022-05-05
 */
@Service
public class CourseServiceImpl extends ServiceImpl<CourseMapper, Course> implements CourseService {

    @Autowired
    private CourseDescriptionService courseDescriptionService;

    @Autowired
    private VideoService videoService;

    @Autowired
    private ChapterService chapterService;

    /***********************************
     * 用途说明:保存课程基本信息和课程简介
     * 返回值说明: com.stu.service.edu.entity.Course
     ***********************************/
    @Transactional(rollbackFor = Exception.class)
    @Override
    public Course saveCourseInfo(CourseInfoForm courseInfoForm) {

        //保存课程基本信息
        Course course = new Course();
        BeanUtils.copyProperties(courseInfoForm, course);
        course.setStatus(CourseConstant.STATUS_DRAFT);//未发布
        baseMapper.insert(course);

        //保存课程简介
        CourseDescription courseDescription = new CourseDescription();
        courseDescription.setDescription(courseInfoForm.getDescription());
        //设置课程和描述是一对一的关系，即课程id和描述id相等。
        //EduCourseDescription实体类主键生成策略改为input。
        courseDescription.setId(course.getId());
        courseDescriptionService.save(courseDescription);

        return course;
    }

    /***********************************
     * 用途说明:取得课程的基本信息和课程简介
     * 返回值说明: com.stu.service.edu.entity.form.CourseInfoForm
     ***********************************/
    @Override
    public CourseInfoForm getCourseForm(String id) {
        return baseMapper.getCourseForm(id);
    }

    /***********************************
     * 用途说明:更新课程基本信息和课程简介
     * 返回值说明: boolean
     ***********************************/
    @Transactional(rollbackFor = Exception.class)
    @Override
    public boolean updateCourseForm(CourseInfoForm courseInfoForm) {
        //课程基本信息
        Course course = new Course();
        BeanUtils.copyProperties(courseInfoForm, course);
        int countUpdate = baseMapper.updateById(course);

        //课程简介
        CourseDescription courseDescription = new CourseDescription();
        courseDescription.setId(course.getId());
        courseDescription.setDescription(courseInfoForm.getDescription());

        boolean countUpdateDescriptiong = courseDescriptionService.updateById(courseDescription);

        return (countUpdate > 0 && countUpdateDescriptiong);
    }

    /***********************************
     * 用途说明:
     * @param courseId
     * 返回值说明:查询课程发布信息
     * @return com.stu.service.edu.entity.vo.CoursePublishVo
     ***********************************/
    @Override
    public CoursePublishVo getCoursePublishById(String courseId) {
        return baseMapper.getCoursePublishById(courseId);
    }

    @Override
    public boolean publishCourse(String id) {
        Course course = new Course();
        course.setId(id);
        course.setStatus(CourseConstant.STATUS_NORMAL);
        return baseMapper.updateById(course) > 0;
    }

    /***********************************
     * 用途说明:课程分页
     * @param page
     * @param limit
     * @param courseQueryVo
     * 返回值说明:
     * @return com.baomidou.mybatisplus.core.metadata.IPage<com.stu.service.edu.entity.vo.CoursePublishVo>
     ***********************************/
    @Override
    public IPage<CourseVo> pageCourses(Long page, Long limit, CourseQueryVo courseQueryVo) {

        QueryWrapper<CourseVo> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("t1.gmt_modified").orderByDesc("t1.id");

        String title = courseQueryVo.getTitle();

        if (!StringUtils.isEmpty(title)) {
            queryWrapper.like("t1.title", title);
        }
        Page<CourseVo> pageParam = new Page<>(page, limit);
        List<CourseVo> coursePublishVos = baseMapper.pageCourses(pageParam, queryWrapper);
        pageParam.setRecords(coursePublishVos);
        return pageParam;
    }

    /***********************************
     * 用途说明:根據id刪除課程（包括课时，小节，详情等）
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    @Transactional(rollbackFor = Exception.class)
    @Override
    public boolean deleteById(String id) {
        boolean result = false;
        //删除video课时
        boolean videoResult = videoService.removeVideoByCourseId(id);
        //删除description课程详情
        QueryWrapper<Chapter> chapterQueryWrapper = new QueryWrapper<Chapter>();
        chapterQueryWrapper.eq("course_id", id);
        boolean chapterResult = chapterService.remove(chapterQueryWrapper);

        boolean desResult = courseDescriptionService.removeById(id);

        //删除course课程
        int courseResult = baseMapper.deleteById(id);
        if (videoResult && chapterResult && courseResult > 0) {
            return true;
        } else {
            result = false;
            throw new CustomException(ResultCodeEnum.UPDATE_ERROR);


        }

    }

    /***********************************
     * 用途说明:根据游览数量取得热门课程
     * 返回值说明:
     * @return java.util.List<com.stu.service.edu.entity.Course>
     ***********************************/
    @Cacheable(value = "index", key = "'listHotCourses'")
    @Override
    public List<Course> listHotCourses() {
        QueryWrapper<Course> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("view_count");
        queryWrapper.last("limit 8");
        return baseMapper.selectList(queryWrapper);
    }

    /***********************************
     * 用途说明:根据讲师id查询所有课程
     * @param id
     * 返回值说明:
     * @return java.util.List<com.stu.service.edu.entity.Course>
     ***********************************/
    @Override
    public List<Course> listCourseByTeacherId(String id) {
        QueryWrapper<Course> queryWrapper = new QueryWrapper<>();
        queryWrapper.orderByDesc("gmt_modified");
        queryWrapper.eq("teacher_id", id);
        return baseMapper.selectList(queryWrapper);
    }

    /***********************************
     * 用途说明:前端课程分页nuxt
     * @param pageParam
     * @param courseQueryVo
     * 返回值说明:
     * @return java.util.Map<java.lang.String, java.lang.Object>
     ***********************************/
    @Override
    public Map<String, Object> listPageCourses(Page<Course> pageParam, CourseQueryVo courseQueryVo) {
        QueryWrapper<Course> queryWrapper = new QueryWrapper<>();
        if (null != courseQueryVo) {
            String subjectParentId = courseQueryVo.getSubjectParentId();
            String subjectId = courseQueryVo.getSubjectId();
            //"销量排序"
            String buyCountSort = courseQueryVo.getBuyCountSort();
            //"最新时间排序"
            String gmtCreateSort = courseQueryVo.getGmtCreateSort();
            //"价格排序"
            String priceSort = courseQueryVo.getPriceSort();

            if (StringUtils.isNotEmpty(subjectParentId)) {
                queryWrapper.eq("subject_parent_id", subjectParentId);
            }
            if (StringUtils.isNotEmpty(subjectId)) {
                queryWrapper.eq("subject_id", subjectId);
            }
            if (StringUtils.isNotEmpty(buyCountSort)) {
                queryWrapper.orderByDesc("buy_count");
            }
            if (StringUtils.isNotEmpty(gmtCreateSort)) {
                queryWrapper.orderByDesc("gmt_create");
            }
            if (StringUtils.isNotEmpty(priceSort)) {
                queryWrapper.orderByDesc("price");
            }
        }
        baseMapper.selectPage(pageParam, queryWrapper);
        Map<String, Object> mapParam = new HashMap<>();
        mapParam.put("items", pageParam.getRecords());//当前页记录
        mapParam.put("current", pageParam.getCurrent());//当前页
        mapParam.put("pages", pageParam.getPages());//共有多少页
        mapParam.put("size", pageParam.getSize());//每页的记录数
        mapParam.put("total", pageParam.getTotal());//总记录数
        mapParam.put("hasNext", pageParam.hasNext());//是否有上一页
        mapParam.put("hasPrevious", pageParam.hasPrevious());//是否有下一页
        return mapParam;
    }

    /***********************************
     * 用途说明:根据课程id查询详情nuxt
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.ApiCourseVo
     ***********************************/
    @Override
    public ApiCourseVo getApiCourseById(String id) {
        this.updateViewCount(id);
        return baseMapper.getApiCourseById(id);
    }

    /***********************************
     * 用途说明:更新游览数
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    @Override
    public boolean updateViewCount(String id) {
        Course course = baseMapper.selectById(id);
        course.setViewCount(course.getViewCount() + 1);
        return baseMapper.updateById(course) > 0;
    }

    /***********************************
     * 用途说明:根据课程id查询订单相关的课程信息
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.CourseApiVo
     ***********************************/
    @Override
    public CourseDto getCourseById(String id) {
        return baseMapper.getCourseById(id);
    }

    /***********************************
     * 用途说明:更新課程銷售量
     * @param id
     * 返回值说明:
     * @return boolean
     ***********************************/
    @Override
    public boolean updateBuyCountById(String id) {
        Course course = baseMapper.selectById(id);
        course.setBuyCount(course.getBuyCount() + 1);
        return baseMapper.updateById(course) > 0;


    }
}

mapper文件

package com.stu.service.edu.mapper;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.toolkit.Constants;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.stu.service.edu.entity.Course;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.stu.service.edu.entity.form.CourseInfoForm;
import com.stu.service.edu.entity.vo.ApiCourseVo;
import com.stu.service.base.dto.CourseDto;
import com.stu.service.edu.entity.vo.CoursePublishVo;
import com.stu.service.edu.entity.vo.CourseVo;
import org.apache.ibatis.annotations.Param;

import java.util.List;

/**
 * <p>
 * 课程 Mapper 接口
 * </p>
 *
 * @author stu
 * @since 2022-05-05
 */
public interface CourseMapper extends BaseMapper<Course> {

    /***********************************
     * 用途说明:取得课程的基本信息和课程简介
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.form.CourseInfoForm
     ***********************************/
    CourseInfoForm getCourseForm(String id);

    /***********************************
     * 用途说明:查询发布课程信息
     * @param courseId
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.CoursePublishVo
     ***********************************/
    CoursePublishVo getCoursePublishById(String courseId);

    /***********************************
     * 用途说明:课程列表
     * @param pageParam
     * @param queryWrapper
     * 返回值说明:
     * @return java.util.List<com.stu.service.edu.entity.vo.CoursePublishVo>
     ***********************************/
    List<CourseVo> pageCourses(Page<CourseVo> pageParam, @Param(Constants.WRAPPER)QueryWrapper<CourseVo> queryWrapper);


    /***********************************
     * 用途说明:根据课程id查询详情nuxt
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.ApiCourseVo
     ***********************************/
    ApiCourseVo getApiCourseById(String id);

    /***********************************
     * 用途说明:根据课程id查询订单相关的课程信息
     * @param id
     * 返回值说明:
     * @return com.stu.service.edu.entity.vo.CourseApiVo
     ***********************************/
    CourseDto getCourseById(String id);

}

xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.stu.service.edu.mapper.CourseMapper">
    <resultMap id="baseBesultMap" type="com.stu.service.edu.entity.form.CourseInfoForm">
        <id column="id" property="id"/>
        <result column="teacher_id" property="teacherId"/>
        <result column="subject_id" property="subjectId"/>
        <result column="subject_parent_id" property="subjectParentId"/>
        <result column="title" property="title"/>
        <result column="price" property="price"/>
        <result column="lesson_num" property="lessonNum"/>
        <result column="cover" property="cover"/>
        <result column="description" property="description"/>
    </resultMap>

    <select id="getCourseForm" resultMap="baseBesultMap">
        SELECT t1.id,
               t1.teacher_id,
               t1.subject_id,
               t1.subject_parent_id,
               t1.title,
               t1.price,
               t1.lesson_num,
               t1.cover,
               t2.description
        FROM edu_course t1
                 LEFT JOIN edu_course_description t2 ON t1.id = t2.id
        WHERE t1.id = #{id}
    </select>
    <select id="getCoursePublishById" parameterType="java.lang.String"
            resultType="com.stu.service.edu.entity.vo.CoursePublishVo">
        SELECT t1.id,
               t1.title,
               t1.price,
               t1.cover,
               t1.lesson_num,
               td.description,
               t3.title AS subjectLevelOne,
               t4.title AS subjectLevelTwo,
               t2.NAME  AS teacherName,
               t3.id,
               t1.subject_id,
               t4.parent_id
        FROM edu_course t1
                 LEFT JOIN edu_course_description td ON td.id = t1.id
                 LEFT JOIN edu_teacher t2 ON t2.id = t1.teacher_id
                 LEFT JOIN edu_subject t3 ON t3.id = t1.subject_parent_id
                 LEFT JOIN edu_subject t4 ON t4.id = t1.subject_id
        WHERE t1.id = #{courseId}
    </select>

    <!--课程分页-->
    <select id="pageCourses" resultType="com.stu.service.edu.entity.vo.CourseVo">
        SELECT t1.id,
               t1.title,
               t1.cover,
               t1.lesson_num   AS lessonNum,
               t1.price,
               t1.buy_count    AS buyCount,
               t1.view_count   AS viewCount,
               t1.`status`,
               t1.gmt_create   AS gmtCreate,
               t1.gmt_modified AS gmtModified,
               t3.title        AS subjectParentTitle,
               t4.title        AS subjectTitle,
               t2.NAME         AS teacherName,
               td.description
        FROM edu_course t1
                 LEFT JOIN edu_course_description td ON td.id = t1.id
                 LEFT JOIN edu_teacher t2 ON t2.id = t1.teacher_id
                 LEFT JOIN edu_subject t3 ON t3.id = t1.subject_parent_id
                 LEFT JOIN edu_subject t4 ON t4.id = t1.subject_id
            ${ew.customSqlSegment}
    </select>
    <!--课程详情-->
    <select id="getApiCourseById" parameterType="java.lang.String"
            resultType="com.stu.service.edu.entity.vo.ApiCourseVo">
        SELECT
            t1.id,
            t1.title,
            t1.price,
            t1.cover,
            t1.lesson_num,
            t1.buy_count,
            t1.view_count,
            t1.STATUS,
            t1.subject_parent_id AS subjectParentId,
            t1.subject_id AS subjectId,
            td.description,
            t2.intro,
            t2.avatar,
            t2.id AS teacherId,
            t3.title AS subjectParentTitle,
            t4.title AS subjectTitle,
            t2.NAME AS teacherName
        FROM
            edu_course t1
        LEFT JOIN edu_course_description td ON td.id = t1.id
        LEFT JOIN edu_teacher t2 ON t2.id = t1.teacher_id
        LEFT JOIN edu_subject t3 ON t3.id = t1.subject_parent_id
        LEFT JOIN edu_subject t4 ON t4.id = t1.subject_id
        WHERE
            t1.id = #{id}
    </select>

    <select id="getCourseById" resultType="com.stu.service.base.dto.CourseDto">
        SELECT
            t1.id,
            t1.title,
            t1.price,
            t1.cover,
            t2.NAME AS teacherName
        FROM
            edu_course t1
        LEFT JOIN edu_teacher t2
        ON t2.id = t1.teacher_id
        WHERE
            t1.id = #{id}
    </select>

</mapper>

 

原文地址：http://www.cnblogs.com/konglxblog/p/16794090.html

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