1.匯入依賴

2.application.properties只需要資料庫連線資訊就可以

3.目錄結構 有個沒用的service，請忽略

4.Controller,因為入門列子，所以簡單的匯出 匯入讀取資料都是可以的

貼上程式碼-》

package com.idress.action;

import com.idress.entity.User;
import com.idress.service.UserService;
import com.idress.utils.ExcelUtils;
import org.apache.poi.hpsf.DocumentSummaryInformation;
import org.apache.poi.hpsf.SummaryInformation;
import org.apache.poi.poifs.filesystem.POIFSFileSystem;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

import org.apache.poi.hssf.usermodel.HSSFCell;
import org.apache.poi.hssf.usermodel.HSSFCellStyle;
import org.apache.poi.hssf.usermodel.HSSFDataFormat;
import org.apache.poi.hssf.usermodel.HSSFFont;
import org.apache.poi.hssf.usermodel.HSSFRow;
import org.apache.poi.hssf.usermodel.HSSFSheet;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletResponse;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

@Controller
public class ExcelController {

    @Autowired
    private UserService userService;

    @RequestMapping("/")
    public String toIndex(){
        return "poi";
    }

    @RequestMapping("/excel/upload")
    public String fileUpload(@RequestParam("file") MultipartFile file) throws IOException {
        if(!ExcelUtils.validateExcel(file.getOriginalFilename())){
            System.out.println("檔案必須是excel!");
            return null;
        }

        long size=file.getSize();
        if(file.getOriginalFilename()==null || file.getOriginalFilename().equals("") || size==0){
            System.out.println("檔案不能為空");
            return null;
        }

        HSSFWorkbook workbook = new HSSFWorkbook(new POIFSFileSystem(file.getInputStream()));

        int numberOfSheets = workbook.getNumberOfSheets();//獲得有多少sheet
        HSSFSheet sheet = workbook.getSheetAt(0);//預設只有一個sheet

        int rows = sheet.getPhysicalNumberOfRows();//獲得sheet有多少行
        //遍歷行
        for (int j = 0; j < rows; j++) {
            if (j == 0) {
                continue;//標題行(省略)
            }
            HSSFRow row = sheet.getRow(j);
            for (int k = 0; k < row.getPhysicalNumberOfCells(); k++) {
                HSSFCell cell = row.getCell(k);
                System.out.println(cell.toString());
            }
        }
        return "poi";
    }

    //生成user表excel
    @GetMapping(value = "/excel/getUser")
    @ResponseBody
    public String getUser(HttpServletResponse response) throws Exception{
        HSSFWorkbook workbook = new HSSFWorkbook();
        HSSFSheet sheet = workbook.createSheet("統計表");
        createTitle(workbook,sheet);
        List<User> rows = new ArrayList<>();//userService.getAll();
        rows.add(new User("1","小明","牛逼",new Date()));
        rows.add(new User("2","中明","牛2逼",new Date()));

        //設定日期格式
        HSSFCellStyle style = workbook.createCellStyle();
        style.setDataFormat(HSSFDataFormat.getBuiltinFormat("m/d/yy h:mm"));

        //新增資料行，並且設定單元格資料
        int rowNum=1;
        for(User user:rows){
            HSSFRow row = sheet.createRow(rowNum);
            row.createCell(0).setCellValue(user.getId());
            row.createCell(1).setCellValue(user.getName());
            row.createCell(2).setCellValue(user.getUsername());
            HSSFCell cell = row.createCell(3);
            cell.setCellValue(user.getCreate_time());
            cell.setCellStyle(style);
            rowNum++;
        }

        String fileName = "匯出excel例子.xls";
        //生成excel檔案
        buildExcelFile(fileName, workbook);
        //瀏覽器下載excel
        buildExcelDocument(fileName,workbook,response);

        return "download excel";
    }

    //建立表頭
    private void createTitle(HSSFWorkbook workbook,HSSFSheet sheet){
        HSSFRow row = sheet.createRow(0);
        //設定列寬，setColumnWidth的第二個引數要乘以256，這個引數的單位是1/256個字元寬度
        sheet.setColumnWidth(1,12*256);
        sheet.setColumnWidth(3,17*256);

        //設定為居中加粗
        HSSFCellStyle style = workbook.createCellStyle();
        HSSFFont font = workbook.createFont();
        font.setBold(true);
        //style.setAlignment(HSSFCellStyle.ALIGN_CENTER);
        style.setFont(font);

        HSSFCell cell;
        cell = row.createCell(0);
        cell.setCellValue("ID");
        cell.setCellStyle(style);

        cell = row.createCell(1);
        cell.setCellValue("顯示名");
        cell.setCellStyle(style);

        cell = row.createCell(2);
        cell.setCellValue("使用者名稱");
        cell.setCellStyle(style);

        cell = row.createCell(3);
        cell.setCellValue("建立時間");
        cell.setCellStyle(style);
    }

    //生成excel檔案
    protected void buildExcelFile(String filename,HSSFWorkbook workbook) throws Exception{
        FileOutputStream fos = new FileOutputStream(filename);
        workbook.write(fos);
        fos.flush();
        fos.close();
    }

    //瀏覽器下載excel
    protected void buildExcelDocument(String filename,HSSFWorkbook workbook,HttpServletResponse response) throws Exception{
        response.setContentType("application/vnd.ms-excel");
        response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(filename, "utf-8"));
        OutputStream outputStream = response.getOutputStream();
        workbook.write(outputStream);
        outputStream.flush();
        outputStream.close();
    }

}

實體類：

import java.util.Date;

public class User {
    private String id;
    private String name;
    private String username;
    private Date create_time;

    public User() {
    }

    public User(String id, String name, String username, Date create_time) {
        this.id = id;
        this.name = name;
        this.username = username;
        this.create_time = create_time;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Date getCreate_time() {
        return create_time;
    }

    public void setCreate_time(Date create_time) {
        this.create_time = create_time;
    }
}

上傳檔案用來讀取資料的html（使用了thymeleaf）

<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
    <base th:href="${#httpServletRequest.getContextPath()+'/'}">
    <meta charset="UTF-8">
    <title>匯入Excel資料</title>
</head>
<body>
<h1>這是使用者資訊頁</h1>

    <form action="excel/upload" method="post" enctype="multipart/form-data">

        <input name="file" type="file" />
        <input type="submit"/>
    </form>


</body>
</html>