SpringBoot+Vue3实现文件的上传和下载功能

<!-- 附件上传 -->
<el-form-item label="上传图片" ref="uploadElement">
    <el-upload
        class="upload-demo"
        action="/api/file/uploadFile"
        :limit="5"
        :on-success="uploadFileSuccess" 
    >
        <el-button type="primary">添加附件</el-button>
        <template #tip>
            <div class="el-upload__tip">
                pdf, md, word格式均可
            </div>
        </template>
    </el-upload>
</el-form-item>

// 上传文件返回函数，为了得到后端返回的下载url，保存到数据库中
uploadFileSuccess(response, file, fileList) {
    let filePath = response.data;
    // 上传文件成功后的response参数已经是返回报文中的data部分，不需要使用response.data.data
    alert(response.data);
    // 回调函数中的this指针就是当前页面vue对象
    this.attachForm.downloadUrl = filePath;
}

@PostMapping("/uploadFile")
public String uploadFile(@RequestParam("file") MultipartFile file, HttpServletRequest request) throws IllegalStateException, IOException{

    // TODO： 文件保存文件夹，后期可以换成配置文件中的内容
    String path = "D:\\uploadfiles";
    String result = "";
    // 调用fileService保存文件
    result = fileService.storeFile(file, path);
    logger.info("文件已保存至" + result);
    return result;
}

/**
* 存储文件到系统
 *
 * @param file 文件
 * @path 保存路径
 * @return 文件名
 * @throws IOException
 * @throws IllegalStateException
 */
@Override
public String storeFile(MultipartFile file, String path) throws IllegalStateException, IOException {
    // 获取原始文件名
    String fileName = file.getOriginalFilename();
    // // 获取文件后缀
    // String suffixName = fileName.contains(".") ? fileName.substring(fileName.lastIndexOf(".")) : null;
    // //文件的保存重新按照时间戳命名
    // String newFileName = System.currentTimeMillis() + suffixName;
    // 最终保存的文件
    File filePath = new File(path + File.separator + fileName);
    // 判断文件夹是否存在
    if (!filePath.getParentFile().exists()) {
        filePath.getParentFile().mkdirs();
    }
    // 保存文件
    file.transferTo(filePath);
    // 如果成功，会返回文件的绝对路径，方便下载
    logger.info("文件已保存至" +filePath.toString());
    return filePath.toString();
}

@RequestMapping("/downloadFile")
public void downloadFiles(@RequestParam("file") String downUrl, HttpServletRequest request, HttpServletResponse response){
  OutputStream outputStream=null;
  InputStream inputStream=null;
  BufferedInputStream bufferedInputStream=null;
  byte[] bytes=new byte[1024];
  File file = new File(downUrl);
  String fileName = file.getName();
  logger.info("本次下载的文件为" + downUrl);
  // 获取输出流
  try {
      // StandardCharsets.ISO_8859_1 *=UTF-8'
      // response.setHeader("Content-Disposition", "attachment;filename=" +  new String(fileName.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1));
      response.setHeader("Content-Disposition", "attachment;filename=" +  URLEncoder.encode(fileName, "UTF-8"));
      // 以流的形式返回文件
      response.setContentType("application/octet-stream;charset=utf-8");
      inputStream = new FileInputStream(file);
      bufferedInputStream = new BufferedInputStream(inputStream);
      outputStream = response.getOutputStream();
      int i = bufferedInputStream.read(bytes);
      while (i!=-1){
          outputStream.write(bytes,0,i);
          i = bufferedInputStream.read(bytes);
      }
  } catch (IOException e) {
      e.printStackTrace();
  }finally {
      try {
          if (inputStream!=null){
              inputStream.close();
          }
          if (outputStream!=null){
              outputStream.close();
          }
          if (bufferedInputStream!=null){
              bufferedInputStream.close();
          }
      } catch (IOException e) {
          e.printStackTrace();
      }

  }

downloadAttach(url) {
    let _this = this;
    // 发送get请求
    this.$axios
    .get('/api/file/downloadFile', {
        params: {
            // 向后端传入下载路径
            file: url,
        }
    })
    .then(res => {
        // alert("请求成功");
        console.log(res.data); // 获取服务端提供的数据
        let blob = new Blob([res.data])
        let contentDisposition = res.headers['content-disposition']
        let pattern = new RegExp('filename=([^;]+\\.[^\\.;]+);*')
        let result = pattern.exec(contentDisposition)
        // 使用decodeURI对名字进行解码
        let fileName = decodeURI(result[1])
        let downloadElement = document.createElement('a')
        // 创建下载的链接
        let href = window.URL.createObjectURL(blob)
        downloadElement.style.display = 'none'
        downloadElement.href = href
        // 下载后文件名
        downloadElement.download = fileName
        document.body.appendChild(downloadElement)
        // 点击下载
        downloadElement.click()
        // 下载完成移除元素
        document.body.removeChild(downloadElement)
        // 释放掉blob对象
        window.URL.revokeObjectURL(href)
    })
    .catch(() => {
        alert("请求出错");
    })
    // alert(url);
}