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;
    }
}

三、分类列表前端实现

1、参考 views/tree/index.vue

2、创建api

api/edu/subject.js

import request from '@/utils/request'
const api_name = '/admin/edu/subject'
export default {
  getNestedTreeList() {
    return request({
      url: `${api_name}`,
      method: 'get'
    })
  }
}

3、list.vue

<template>
  <div class="app-container">
    <el-input v-model="filterText" placeholder="Filter keyword" style="margin-bottom:30px;" />
    <el-tree
      ref="subjectTree"
      :data="subjectList"
      :props="defaultProps"
      :filter-node-method="filterNode"
      class="filter-tree"
      default-expand-all
    />
  </div>
</template>
<script>
import subject from '@/api/edu/subject'
export default {
  data() {
    return {
      filterText: '',
      subjectList: [],
      defaultProps: {
        children: 'children',
        label: 'title'
      }
    }
  },
  watch: {
    filterText(val) {
      this.$refs.subjectTree.filter(val)
    }
  },
  created() {
    this.fetchNodeList()
  },
  methods: {
    fetchNodeList() {
      subject.getNestedTreeList().then(response => {
        if (response.success === true) {
          this.subjectList = response.data.items
        }
      })
    },
    filterNode(value, data) {
      if (!value) return true
      return data.title.indexOf(value) !== -1
    }
  }
}
</script>

四、分类列表后端实现

1、创建vo

package com.guli.edu.vo;
@Data
public class SubjectVo {
    private String id;
    private String title;
}

package com.guli.edu.vo;
@Data
public class SubjectNestedVo {
    private String id;
    private String title;
    private List<SubjectVo> children = new ArrayList<>();
}

2、创建controller

@ApiOperation(value = "嵌套数据列表")
@GetMapping("")
public R nestedList(){
    List<SubjectNestedVo> subjectNestedVoList = subjectService.nestedList();
    return R.ok().data("items", subjectNestedVoList);
}

3、创建service

接口

List<SubjectNestedVo> nestedList();

实现Final

@Override
public List<SubjectNestedVo> nestedList() {
    //最终要的到的数据列表
    ArrayList<SubjectNestedVo> subjectNestedVoArrayList = new ArrayList<>();
    //获取一级分类数据记录
    QueryWrapper<Subject> queryWrapper = new QueryWrapper<>();
    queryWrapper.eq("parent_id", 0);
    queryWrapper.orderByAsc("sort", "id");
    List<Subject> subjects = baseMapper.selectList(queryWrapper);
    //获取二级分类数据记录
    QueryWrapper<Subject> queryWrapper2 = new QueryWrapper<>();
    queryWrapper2.ne("parent_id", 0);
    queryWrapper2.orderByAsc("sort", "id");
    List<Subject> subSubjects = baseMapper.selectList(queryWrapper2);
    //填充一级分类vo数据
    int count = subjects.size();
    for (int i = 0; i < count; i++) {
        Subject subject = subjects.get(i);
        //创建一级类别vo对象
        SubjectNestedVo subjectNestedVo = new SubjectNestedVo();
        BeanUtils.copyProperties(subject, subjectNestedVo);
        subjectNestedVoArrayList.add(subjectNestedVo);
        //填充二级分类vo数据
        ArrayList<SubjectVo> subjectVoArrayList = new ArrayList<>();
        int count2 = subSubjects.size();
        for (int j = 0; j < count2; j++) {
            Subject subSubject = subSubjects.get(j);
            if(subject.getId().equals(subSubject.getParentId())){
                //创建二级类别vo对象
                SubjectVo subjectVo = new SubjectVo();
                BeanUtils.copyProperties(subSubject, subjectVo);
                subjectVoArrayList.add(subjectVo);
            }
        }
        subjectNestedVo.setChildren(subjectVoArrayList);
    }
    return subjectNestedVoArrayList;
}

五、优化前端过滤功能

filterNode(value, data) {
    if (!value) return true
    return data.title.toLowerCase().indexOf(value.toLowerCase()) !== -1
}