一、添加依赖

1、service-edu模块****配置依赖

<dependencies>
    <!-- https://mvnrepository.com/artifact/com.alibaba/easyexcel -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>easyexcel</artifactId>
        <version>2.1.1</version>
    </dependency>
</dependencies>

二、业务处理

1、SubjectAdminController

package com.guli.edu.controller.admin;
@Api(description="课程分类管理")
@CrossOrigin //跨域
@RestController
@RequestMapping("/eduservice/subject")
public class SubjectAdminController {

    @Autowired
    private SubjectService subjectService;

    //添加课程分类
    @ApiOperation(value = "Excel批量导入")
    @PostMapping("addSubject")
    public R addSubject(MultipartFile file) {
        //1 获取上传的excel文件 MultipartFile
        //返回错误提示信息
        subjectService.importSubjectData(file,subjectService);
        //判断返回集合是否为空
        return R.ok();
    }
}

2、创建和Excel对应的实体类

import com.alibaba.excel.annotation.ExcelProperty;
import lombok.Data;

@Data
public class ExcelSubjectData {
    @ExcelProperty(index = 0)
    private int oneSubjectName;

    @ExcelProperty(index = 1)
    private String twoSubjectName;
}

3、SubjectService

（1）接口

void batchImport(MultipartFile file);

（2）实现类

//添加课程分类
//poi读取excel内容
@Override
public void importSubjectData(MultipartFile file,EduSubjectService subjectService) {
    try {
        //1 获取文件输入流
        InputStream inputStream = file.getInputStream();

        // 这里 需要指定读用哪个class去读，然后读取第一个sheet 文件流会自动关闭
        EasyExcel.read(inputStream, ExcelSubjectData.class, new SubjectExcelListener(subjectService)).sheet().doRead();
    }catch(Exception e) {
        e.printStackTrace();
        throw new GuliException(20002,"添加课程分类失败");
    }
}

4、创建读取Excel监听器

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

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

public class SubjectExcelListener extends AnalysisEventListener<ExcelSubjectData> {

    public EduSubjectService subjectService;
    
    public SubjectExcelListener() {}
    //创建有参数构造，传递subjectService用于操作数据库
    public SubjectExcelListener(EduSubjectService subjectService) {
        this.subjectService = subjectService;
    }

    //一行一行去读取excle内容
    @Override
    public void invoke(ExcelSubjectData user, AnalysisContext analysisContext) {
        if(user == null) {
            throw new GuliException(20001,"添加失败");
        }
        //添加一级分类
        EduSubject existOneSubject = this.existOneSubject(subjectService,user.getOneSubjectName());
        if(existOneSubject == null) {//没有相同的
            existOneSubject = new EduSubject();
            existOneSubject.setTitle(user.getOneSubjectName());
            existOneSubject.setParentId("0");
            subjectService.save(existOneSubject);
        }

        //获取一级分类id值
        String pid = existOneSubject.getId();
        
        //添加二级分类
        EduSubject existTwoSubject = this.existTwoSubject(subjectService,user.getTwoSubjectName(), pid);
        if(existTwoSubject == null) {
            existTwoSubject = new EduSubject();
            existTwoSubject.setTitle(user.getTwoSubjectName());
            existTwoSubject.setParentId(pid);
            subjectService.save(existTwoSubject);
        }
    }

    //读取excel表头信息
    @Override
    public void invokeHeadMap(Map<Integer, String> headMap, AnalysisContext context) {
        System.out.println("表头信息："+headMap);
    }

    //读取完成后执行
    @Override
    public void doAfterAllAnalysed(AnalysisContext analysisContext) {}

    //判断一级分类是否重复
    private EduSubject existTwoSubject(EduSubjectService subjectService,String name,String pid) {
        QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
        wrapper.eq("title",name);
        wrapper.eq("parent_id",pid);
        EduSubject eduSubject = subjectService.getOne(wrapper);
        return eduSubject;
    }

    //判断一级分类是否重复
    private EduSubject existOneSubject(EduSubjectService subjectService,String name) {
        QueryWrapper<EduSubject> wrapper = new QueryWrapper<>();
        wrapper.eq("title",name);
        wrapper.eq("parent_id","0");
        EduSubject eduSubject = subjectService.getOne(wrapper);
        return eduSubject;
    }
}