1.使用代码生成器，生成课程分类代码

把我们原先的代码生成器打开，修改一下，然后运行。

运行之后：出现了新生成的文件

2.创建实体类，和excel有对应关系

4.编写service方法

编写监听器代码：

整个监听器代码：

package com.atguigu.eduservice.listener;

import com.alibaba.excel.context.AnalysisContext;
import com.alibaba.excel.event.AnalysisEventListener;
import com.atguigu.eduservice.entity.EduSubject;
import com.atguigu.eduservice.entity.excel.SubjectData;
import com.atguigu.eduservice.service.EduSubjectService;
import com.atguigu.servicebase.exceptionhandler.GuliException;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;

public class SubjectExcelListener extends AnalysisEventListener<SubjectData> {
    
    
    //因为SubjectExcelListener不能交给spring进行管理，需要自己new，不能注入其他对象，也不能实现数据库操作
    public EduSubjectService subjectService;

    public SubjectExcelListener() {
    
    
    }
    public SubjectExcelListener(EduSubjectService subjectService) {
    
    
        this.subjectService = subjectService;
    }

    //读取excel内容，一行一行进行读取
    @Override
    public void invoke(SubjectData subjectData, AnalysisContext analysisContext) {
    
    
        if(subjectData == null){
    
    
            throw new GuliException(20001,"文件数据为空");
        }
        //一行一行读取，每次读取有两个值，第一个值是一级分类，第二个值是二级分类
        //1.添加一级分类
        //判断一级分类是否重复
        EduSubject existOneSubject = this.existOneSubject(subjectService,subjectData.getOneSubjectName());
        //表中没有相同的一级分类，进行添加
        if(existOneSubject == null){
    
    
            existOneSubject = new EduSubject();
            existOneSubject.setParentId("0");
            existOneSubject.setTitle(subjectData.getOneSubjectName());
            subjectService.save(existOneSubject);
        }
        
        //2.添加二级分类
        //获取一级分类的id值
        String pid = existOneSubject.getId();
        //判断二级分类是否重复
        EduSubject existTwoSubject = this.existTwoSubject(subjectService,subjectData.getTwoSubjectName(),pid);
        if(existTwoSubject == null){
    
    
            existTwoSubject = new EduSubject();
            existTwoSubject.setParentId(pid);
            existTwoSubject.setTitle(subjectData.getTwoSubjectName());
            subjectService.save(existTwoSubject);
        }
    }
    //判断一级分类不能重复添加
    private EduSubject existOneSubject(EduSubjectService subjectService,String name){
    
    
        QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
        wrapper.eq("title",name);
        wrapper.eq("parent_id","0");
        EduSubject oneSubject = subjectService.getOne(wrapper);
        return oneSubject;
    }
    //判断二级分类不能重复添加
    private EduSubject existTwoSubject(EduSubjectService subjectService,String name,String pid){
    
    
        QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
        wrapper.eq("title",name);
        wrapper.eq("parent_id",pid);
        EduSubject twoSubject = subjectService.getOne(wrapper);
        return twoSubject;
    }

    @Override
    public void doAfterAllAnalysed(AnalysisContext analysisContext) {
    
    

    }
}

5.测试