用HSSFWorkbook生成一个excel，并以流形式返回前端，并自动下载

1 用 HSSFWorkbook 定义excel的格式，并填入数据。
2 将这个文件以response流返回
3 blob形式拿到文件

@Override
	public void exportToExcelTable(List<FeedbackRecord> list, String[] columnName, HttpServletResponse response) throws IOException {
    
    
		Long time = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8"));

		HSSFWorkbook book=new HSSFWorkbook();
		HSSFSheet sheet=book.createSheet("表");
		int num = 0;
		String [][] arr = new String[list.size()][12];
		for (FeedbackRecord feedbackRecord : list){
    
    
			BeanMap beanMap = BeanMap.create(feedbackRecord);

			beanMap = checkNullAndEnglishCode(beanMap);
			arr [num][0] = beanMap.get("userName").toString();
			arr [num][1] = beanMap.get("feedbackTime").toString().replace("T"," ");
			arr [num][2] = beanMap.get("feedbackTitle").toString();
			arr [num][3] = beanMap.get("type").toString();
			arr [num][4] = beanMap.get("feedbackContent").toString();
			arr [num][5] = beanMap.get("channel").toString();
			arr [num][6] = beanMap.get("checkStatus").toString();
			arr [num][7] = beanMap.get("adoptStatus").toString();
			arr [num][8] = beanMap.get("realizeStatus").toString();
			arr [num][9] = beanMap.get("replyStatus").toString();
			arr [num][10] = beanMap.get("replyContent").toString();
			arr [num][11] = beanMap.get("isPublic").toString();
			num++;
		}
		//生成表单的第一行，即表头
		HSSFRow row0=sheet.createRow(0);//创建第一行
		for(int i=0;i<12;i++){
    
    
			HSSFCell cel=row0.createCell(i);//创建第一行的第i列
			cel.setCellValue(columnName[i]);
		}
		//从第二行开始，往里添加每列数据
		for(int j=0;j<num;j++){
    
    
			HSSFRow row=sheet.createRow(j+1);//创建非第一行的其他行
			for(int i=0;i<12;i++){
    
    
				HSSFCell cel=row.createCell(i);//创建第j+1行的第i列
				cel.setCellValue(arr[j][i]);
			}
		}
		//用文件输出流类创建Excel表格
//		FileOutputStream out=new FileOutputStream(path);
//		book.write(out);//将HSSFWorkBook中的表写入输出流中

		File file = new File("E:/excel测试/反馈"+time.toString()+".xls");
		
		response.setContentType("application/octet-stream");
		response.setHeader("content-type", "application/octet-stream");
		response.setHeader("Content-Disposition", "attachment;fileName=download");// 设置文件名
		OutputStream os = response.getOutputStream();
		book.write(os);
		//os.write(YaFileUtil.getBytesByFile(file));
		os.flush();
		book.close();
	}

//下载方法
      async downloadUploadInstallPacFile(row) {
    
    
        const Obj = JSON.parse(row.attachmentAddressForm);
        if(Obj!=null){
    
    
          //for循环遍历
          const data = {
    
    
            //这里要注意，json解出来有可能有多个，下载一个文件的话，需要取数组的第一个Obj[0]
            attachmentFileOssLink: Base64.encode(Obj[0].attachmentFileOssLink),
            bucketName: "appversion"
          };
          const result = await downloadAttachedFile(data);
          const url = window.URL.createObjectURL(new Blob([result.data], {
    
    type: 'application/octet-stream'}));
          const link = document.createElement('a');
          link.href = url;
          link.setAttribute('download', Obj[0].attachmentFileName);
          document.body.appendChild(link);
          link.click();
        }
      },

附：通用的blob流形式的下载

downloadFile(file){
    
    
          let type = fileTypeMap[file.itemSuffix];//取文件名后缀，可忽略
          getFileByUrl(file.url).then(result => {
    
    
            const blob = new Blob([result.data], {
    
     type: type });
            let src = window.URL.createObjectURL(blob);//拿到blob地址
            var link = document.createElement('a')//建立a链接
            link.href = src;//配置url
            link.target = "_blank";
            link.setAttribute('download', file.itemName + new Date().toLocaleDateString())//下载类型，并配置文件名
            link.click();//开启下载
          })
        },