最简单容易上手的EasyExcel

1.导入依赖

2.编写监听器

```java
package com.yumchina.cultivate.config;

import com.alibaba.excel.context.AnalysisContext;
import com.alibaba.excel.event.AnalysisEventListener;
import com.yumchina.cultivate.pojo.DscStudent;
import com.yumchina.cultivate.service.ExcelService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;

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

/**
 * @Author: lucy
 * @Date: 2021/11/22 11:43
 */
@Slf4j
@Component
public class ExcelListener extends AnalysisEventListener {

    /**
     * 每隔5条存储数据库，实际使用中可以100条，然后清理list ，方便内存回收  Student 根据情况换成自己需要的实体类   解析出来的数据是保存在cachedDataList 中的
     */
    private static final int BATCH_COUNT = 20;
    private List cachedDataList = new ArrayList<>(BATCH_COUNT+2);
    /**
     * 假设这个是一个DAO，当然有业务逻辑这个也可以是一个service。当然如果不用存储这个对象没用。
     */
    private final ExcelService excelService;

    public ExcelListener(ExcelService excelService) {
        this.excelService = excelService;
    }

    /**
     * 每条数据都调
     * @param
     * @param analysisContext
     */
    @Override
    public void invoke(Student Student, AnalysisContext analysisContext) {
//        log.info("解析到一条数据:{}", JSON.toJSONString(dscStudent));
        cachedDataList.add(dscStudent);
        // 达到BATCH_COUNT了，需要去存储一次数据库，防止数据几万条数据在内存，容易OOM
        if (cachedDataList.size() >= BATCH_COUNT) {
//            saveData();
            // 存储完成清理 list
            cachedDataList = new ArrayList<>(BATCH_COUNT+2);
        }
    }

    /**
     * 所有数据解析完成了 都会来调用
     *
     * @param context
     */
    @Override
    public void doAfterAllAnalysed(AnalysisContext context) {
        // 这里也要保存数据，确保最后遗留的数据也存储到数据库
//        saveData();
        log.info("所有数据解析完成！");
    }

    /**
     * 加上存储数据库
     */
//    private void saveData() {
//        log.info("{}条数据，开始存储数据库！", cachedDataList.size());
//        excelService.readExcelAndCopyDataBase(cachedDataList);
//        log.info("存储数据库成功！");
//    }
    public List getData(){
        return cachedDataList;
    }
}

3编写控制器

@PostMapping("/readStudentExcel")
    public Result readStudentExcel(MultipartFile file){
        try {
        //固定写 DscStudent换成自己的实体类
            EasyExcel.read(file.getInputStream(), DscStudent.class,excelListener).sheet().doRead();
        } catch (IOException e) {
            e.printStackTrace();
        }
        List<DscStudent> data = excelListener.getData();
        for (DscStudent dscStudent:data){
            System.out.println(dscStudent.getStudentName().toString());
        }
        return Result.ok();
    }

4编写pojo

public class Student implements Serializable {
    @ExcelProperty(value = "学生姓名")
    private String studentName;
    private static final long serialVersionUID = 1L;

}

下载Excel

@GetMapping("/reportExcel")
    public void reportExcel(String startTime, String endTime, HttpServletResponse response) throws IOException {
        response.setContentType("application/vnd.ms-excel");
        response.setCharacterEncoding("utf-8");
        //防止中文乱码
        String fileName = URLEncoder.encode("Employeetraintime", "UTF-8");
        //插入自己的查询语言
        //List employeetraintimes = excelService.reportExce(startTime, endTime);
        response.setHeader("Content-disposition", "attachment;filename=" + fileName + ".xlsx");
        //EmployeeTrainTimeVo 为对应的实体类对象
        EasyExcel.write(response.getOutputStream(),EmployeeTrainTimeVo.class).sheet("新工工时").doWrite(employeetraintimes);
    }