1.pom依赖包

        <!--easypoi包是excel导入导出需要-->
        <dependency>
            <groupId>cn.afterturn</groupId>
            <artifactId>easypoi-base</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>cn.afterturn</groupId>
            <artifactId>easypoi-web</artifactId>
            <version>3.2.0</version>
        </dependency>
        <dependency>
            <groupId>cn.afterturn</groupId>
            <artifactId>easypoi-annotation</artifactId>
            <version>3.2.0</version>
        </dependency>

2.要导出的实体字段entity

package com.jk.cs.entity;

import cn.afterturn.easypoi.excel.annotation.Excel;
import lombok.Data;

import java.io.Serializable;
import java.time.LocalDate;

@Data
public class StudentExport implements Serializable {
    //isImportField找不到对应的字段用true_st
    @Excel(name = "学生姓名",height = 20,width = 30,isImportField = "true_st",orderNum = "0")
    private String name;

    @Excel(name = "学生性别",replace = {"男_1","女_2"},suffix = "生",orderNum = "1")
    private Integer sex;

    @Excel(name = "出生日期",databaseFormat = "yyyyMMdd",format = "yyyy-MM-dd",orderNum = "2")
    private LocalDate birthday;

    @Excel(name = "进校日期")
    private LocalDate registrationDate;
}

3.对应导出实体的list集合

mapper中
    List<StudentExport> listExport();

4.controller中用HttpServletRespose流程excel

package com.jk.cs.controller;

import cn.afterturn.easypoi.excel.ExcelExportUtil;
import cn.afterturn.easypoi.excel.entity.ExportParams;
import com.jk.cs.entity.Student;
import com.jk.cs.entity.StudentExport;
import com.jk.cs.service.IStudentService;
import org.apache.poi.ss.usermodel.Workbook;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.net.URLEncoder;
import java.util.List;

/**
 * <p>
 *  前端控制器
 * </p>
 *
 * @author jie
 * @since 2021-09-20
 */
@RestController
@RequestMapping("/student")
public class StudentController {
    @Autowired
    private IStudentService studentService;

    /**
     * 保存和修改
     * @param student
     * @return
     */
    @RequestMapping("/edit")
    public boolean saveStudent(@RequestBody Student student){
        return studentService.saveOrUpdate(student);

    }

    /**
     * studentExport导出
     */
    @RequestMapping("/export")
    public void studentExport(HttpServletResponse response){
        //1.导出的字段list集合
        List<StudentExport> studentExports = studentService.studentExportList();
        //2.下载的excel名称
        String fileName="学生信息.xlsx";

        try {
            //3.设置浏览器下载格式
            response.setCharacterEncoding("UTF-8");
            //文件下载的内容类型
            response.setContentType("application/octet-stream");

            //Content-Disposition提供一个默认的文件名，文件直接在浏览器上显示或者在访问时弹出文件下载对话框
            response.setHeader("Content-Disposition","attachment;filename="+URLEncoder.encode(fileName,"UTF-8"));

            //4.title为文件内开头名，sheetName是对应底下文件名称，第二个参数是需要导出的实体类，第三个参数是list集合
            Workbook exportExcel = ExcelExportUtil.exportExcel(new ExportParams("学生信息", "学生"), StudentExport.class, studentExports);

            //5.流方式输出excel
            exportExcel.write(response.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
}

可以参考excel文档为：http://easypoi.mydoc.io/#text_186905