/**
	 *  文件下载
	 * @param id
	 * @return
	 * @throws IOException
	 */
	@RequestMapping(value = "/download_file/{type}", method = RequestMethod.GET)  
    public void downloadFile(@PathParam("type") Long type,HttpServletResponse res)  
            throws IOException {  
        
        String path = ReadJson.class.getClassLoader().getResource("upgrade.json").getPath();
        res.setHeader("content-type", "application/octet-stream");
        res.setContentType("application/octet-stream");
        res.setHeader("Content-Disposition", "attachment;filename=" + "upgrade.json");
        InputStream in = null;
        OutputStream os = null;
        try {
            os = res.getOutputStream();
            in = new FileInputStream(new File(path));
			byte[] buffer = new byte[1024];
			int len;
			while ((len = in.read(buffer)) > 0) {
				  os.write(buffer, 0, len);
			}
			/**调用os.flush();就表示下载相应构建完成了，相当于return响应数据*/
			os.flush();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
     
    }  

 <el-button size="small" type="primary" @click="downloadFile()">
              下载
            </el-button>


 downloadFile() {
      window.location.href = process.env.VUE_APP_DEV_API + '/upgrad_tcp/download_file/1'
    },