我正在开发一个springboot项目，它使用thymeleaf作为前端。我给用户一个选项，上传一个html（纯html）文件和要求，也是显示预览的html文件之前上传。我可以看到在互联网上有选择预览图像，但我找不到一些html文件预览的例子。有人能帮我做到这一点吗？

<div class="col-md-8 mx-auto">
                <h2>Upload Email Template</h2>
                <p th:text="${message}" th:if="${message ne null}" class="alert alert-primary"></p>
                <form method="post" th:action="@{/upload}" enctype="multipart/form-data">
                  <div class="form-group">
                    <input type="file" name="file" class="form-control-file">
                  </div>
                  <button type="submit" class="btn btn-primary">Upload File</button>
                </form>
              </div>

控制器

@PostMapping("/upload")
    public String uploadFile(@RequestParam("file") MultipartFile file, RedirectAttributes attributes) {

        // check if file is empty
        if (file.isEmpty()) {
            attributes.addFlashAttribute("message", "Please select a file to upload.");
            return "redirect:/";
        }

        // normalize the file path
        String fileName = StringUtils.cleanPath(file.getOriginalFilename());

        // save the file on the local file system
        try {
            Path path = Paths.get(UPLOAD_DIR + fileName);
            Files.copy(file.getInputStream(), path, StandardCopyOption.REPLACE_EXISTING);
            log.info("file upload successful" +path);
        } catch (IOException e) {
            e.printStackTrace();
        }

        // return success response
        attributes.addFlashAttribute("message", "You successfully uploaded " + fileName + '!');

        return "redirect:/monthlyTransactions";
    }