SpringBoot 中Service类中的方法 总结

package com.school.eduservice.service.impl;

import com.alibaba.excel.EasyExcel;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.school.eduservice.entity.EduSubject;
import com.school.eduservice.entity.excel.SubjectData;
import com.school.eduservice.entity.vo.OneSubject;
import com.school.eduservice.entity.vo.TwoSubject;
import com.school.eduservice.listener.SubjectExcelListener;
import com.school.eduservice.mapper.EduSubjectMapper;
import com.school.eduservice.service.EduSubjectService;
import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;


@Service
public class EduSubjectServiceImpl extends ServiceImpl implements EduSubjectService {

    @Override
    public void addFiles(MultipartFile file,EduSubjectService eduSubjectService) {
        try {
            //文件输入流
            InputStream inputStream = file.getInputStream();
            //调用方法读取
            EasyExcel.read(inputStream,SubjectData.class,new SubjectExcelListener(eduSubjectService)).sheet().doRead();
        }catch (Exception e){
              e.printStackTrace();
        }


    }

    @Override
    public List subTree() {

        //查询出一级分类
         QueryWrapper objectQueryWrapper = new QueryWrapper<>();
        objectQueryWrapper.eq("parent_id",0);
        //怎么在 service 中调用 mapper 中的方法查询
        //1.方法一  因为service 类 已经继承的 ServiceImpl 中
        // 已经帮我们注入了 mapper 所以 我们可以直接用
       // List eduSubjects = baseMapper.selectList(objectQueryWrapper);
        //方法二  用 this（当前类）也可以调用 mapper中的方法
        List eduSubjects1 = this.list(objectQueryWrapper);
        List eduSubject2=this.list(new QueryWrapper().ne("parent_id",0));
        List list= new ArrayList<>();
        for (int i=0;i twoSubjects=new ArrayList<>();
           for(int j=0;j