<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>RELEASE</version>
</dependency>
<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi-ooxml</artifactId>
    <version>RELEASE</version>
</dependency>

package com.example.demo.controller;
import com.example.demo.domain.User;
import com.example.demo.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
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 javax.servlet.http.HttpServletResponse;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.List;
@RestController
@RequestMapping(value = "/excel")
public class ExcelController {
    @Autowired
    private UserService userService;
    //创建表头
    private void createTitle(HSSFWorkbook workbook,HSSFSheet sheet){
        HSSFRow row = sheet.createRow(0);
        //设置列宽，setColumnWidth的第二个参数要乘以256，这个参数的单位是1/256个字符宽度
        sheet.setColumnWidth(1,12*256);
        sheet.setColumnWidth(3,17*256);
        //设置为居中加粗
        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("显示名");
        cell.setCellStyle(style);
        cell = row.createCell(2);
        cell.setCellValue("用户名");
        cell.setCellStyle(style);
        cell = row.createCell(3);
        cell.setCellValue("创建时间");
        cell.setCellStyle(style);
    }
    //生成user表excel
    @GetMapping(value = "/getUser")
    public String getUser(HttpServletResponse response) throws Exception{
        HSSFWorkbook workbook = new HSSFWorkbook();
        HSSFSheet sheet = workbook.createSheet("统计表");
        createTitle(workbook,sheet);
        List<User> rows = userService.getAll();
        //设置日期格式
        HSSFCellStyle style = workbook.createCellStyle();
        style.setDataFormat(HSSFDataFormat.getBuiltinFormat("m/d/yy h:mm"));
        //新增数据行，并且设置单元格数据
        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 = "导出excel例子.xls";
        //生成excel文件
        buildExcelFile(fileName, workbook);
        //浏览器下载excel
        buildExcelDocument(fileName,workbook,response);
        return "download excel";
    }
    //生成excel文件
    protected void buildExcelFile(String filename,HSSFWorkbook workbook) throws Exception{
        FileOutputStream fos = new FileOutputStream(filename);
        workbook.write(fos);
        fos.flush();
        fos.close();
    }
    //浏览器下载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();
    }
}