java实现异步导出数据

@RequestMapping("exportExcel") //用户数据导出
 public void exportExcel(HttpServletRequest request, HttpServletResponse response) {
 Map<String,Object> map = new HashMap<String,Object>();
 try{
  EquipmentAccident search=(EquipmentAccident) 
  request.getSession().getAttribute("equipmentAccident1"); //获取保存在session中的查询条件
  if(search !=null ){
  if(Str.isNotNull(search.getName())){ //名称
  map.put("name", search.getName());
  }
  if(Str.isNotNull(search.getRemark())){ //备注
  map.put("remark", search.getRemark());
  }
  }

  List<User> list=userService.selectExcel(map); //查询数据
  
  XSSFWorkbook wb = new XSSFWorkbook(); // 声明一个工作薄
   XSSFSheet sheet = wb.createSheet("用户信息"); // 生成一个表格
 
   Integer columnIndex = 0;
   sheet.setColumnWidth(columnIndex++, 3 * 512); // 设置表格第一列宽度为3个字节 
   sheet.setColumnWidth(columnIndex++, 10 * 512); //名称
   sheet.setColumnWidth(columnIndex++, 10 * 512); //年龄
   sheet.setColumnWidth(columnIndex++, 10 * 512); //备注
   
   // 生成一个样式 
   XSSFCellStyle style1 = wb.createCellStyle(); 
   // 设置这些样式 
   style1.setFillForegroundColor(IndexedColors.GREY_25_PERCENT.getIndex());
   
   // 生成一个字体 
   XSSFFont font1 = wb.createFont(); 
   font1.setFontHeightInPoints((short) 11); 
   font1.setFontName("黑体"); // 字体
   // 把字体应用到当前的样式 
   style1.setFont(font1); 
   
   //在sheet里增加合并单元格 
   CellRangeAddress cra = new CellRangeAddress(0, 0, 0, 7);  
   sheet.addMergedRegion(cra);
   
   int rowInt = 0; //列号
   XSSFRow row = sheet.createRow(rowInt++);
   
   XSSFCell cell = row.createCell(0);
   cell.setCellStyle(style1);
   cell.setCellValue("用户信息");
   
   int cellInt = 0;
   row = sheet.createRow(rowInt++);
   
   cell = row.createCell(cellInt++);
   cell.setCellStyle(style1);
   cell.setCellValue("序号");
   
   cell = row.createCell(cellInt++);
   cell.setCellStyle(style1);
   cell.setCellValue("名称");
   
   cell = row.createCell(cellInt++);
   cell.setCellStyle(style1);
   cell.setCellValue("年龄");
   
   cell = row.createCell(cellInt++);
   cell.setCellStyle(style1);
   cell.setCellValue("备注");
 
   int index = 0;
   if(list!=null && !list.isEmpty()){
    for(User obj:list){
    index++;
    cellInt = 0;
     row = sheet.createRow(rowInt++);
     
     cell = row.createCell(cellInt++);
     cell.setCellValue(index);
     
     cell = row.createCell(cellInt++);
     cell.setCellValue(obj.getName());
     
     cell = row.createCell(cellInt++);
     cell.setCellValue(obj.getAge());
     
     cell = row.createCell(cellInt++);
     cell.setCellValue(obj.getRemark());
    }
   }
   //反馈给前台状态
  response.getWriter().append("ok");
  //XSSFWorkbook对象保持到session里，供下载使用
  request.getSession().setAttribute("XSSFWorkbook",wb);
 } catch (Exception e) {
  e.printStackTrace();
 }
}

 /**
 * @param fileName 下载文件名称
 * @param request 请求对象
 * @param response 响应对象
 * 2020-11-10 新增
*/
 @RequestMapping("downloadExcel")
 public void downloadExcel(String fileName,HttpServletRequest request,HttpServletResponse response) {
 if(Str.isNotNull(fileName)){
 User loginUser = (User) request.getSession().getAttribute("loginUser");
 //检验下载路径并返回url
 String url = FileTool.getdownLoadUrl(loginUser, fileName, request);
 //从url里截取出文件全名
 fileName = url.substring(url.lastIndexOf("/")+1);
 //创建文件输出流
 FileOutputStream fileOut = null; 
 try {
  fileOut = new FileOutputStream(url); 
  //获取保存在session中的待下载数据
  XSSFWorkbook wb = (XSSFWorkbook) request.getSession().getAttribute("XSSFWorkbook");
  wb.write(fileOut);
 } catch (FileNotFoundException e) {
  e.printStackTrace();
 }catch (IOException e) {
  e.printStackTrace();
 }
 
 finally{ 
    if(fileOut != null){ 
     try { 
      fileOut.close(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 
    } 
   } 
   
 try {
   System.out.println("------------开始下载文件---------------");
   File file = new File(url);
    // 以流的形式下载文件。
    InputStream fis = new BufferedInputStream(new FileInputStream(url));
    byte[] buffer = new byte[fis.available()];
    fis.read(buffer);
    fis.close();
    // 清空response
    response.reset();
    // 设置response的Header
    response.addHeader("Content-Disposition", "attachment;filename=" + new 
    String(fileName.getBytes("UTF-8"),
    "ISO8859-1"));
    response.addHeader("Content-Length", "" + file.length());
    OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
    response.setContentType("application/octet-stream");
    toClient.write(buffer);
    toClient.flush();
    toClient.close();
    //清除session里的数据
    request.getSession().removeAttribute("XSSFWorkbook");
   } catch (IOException ex) {
    ex.printStackTrace();
   }
 }
}

 //导出请求
 function exportExcel(){
 var load = saveLoad("导出中，请稍后...",1); //打开一个等待框
 $.ajax({
   type: "post",
   url: "exportExcel",
   dataType:"text",
   error: function(request) {
    closeSaveLoad(load,1);
    return false;
   },
   success: function(msg) {
    if(msg=='ok'){
    closeSaveLoad(load,1); //关闭等待框
    //下载请求地址
    window.location.href="downloadExcel?fileName=用户信息" rel="external nofollow" ;
    }else{
    closeSaveLoad(load,1); //关闭等待框
    layer.msg("导出失败，刷新页面重试",{icon:2});
    return false;
    }
   }
  });
 }