后端根据minio返回的文件下载链接预览excel文件

要在后端预览Minio返回的Excel文件下载链接，您可以使用像Apache POI这样的Java库。Apache POI是一个用于读写Microsoft Office格式文件（例如Excel、Word和PowerPoint）的开源Java库。您可以使用它来读取Excel文件内容，并将其呈现为HTML格式，以便在网页上进行预览。

以下是一个简单的示例，演示如何使用Apache POI和Spring Boot将Excel文件转换为HTML格式：

@GetMapping("/preview")
public String previewExcel(@RequestParam("url") String url, Model model) throws IOException {
    // Create a new HTTP client
    CloseableHttpClient httpClient = HttpClients.createDefault();

    // Send a GET request to Minio to download the Excel file
    HttpGet httpGet = new HttpGet(url);
    CloseableHttpResponse response = httpClient.execute(httpGet);
    InputStream inputStream = response.getEntity().getContent();

    // Use Apache POI to read the Excel file and convert it to HTML
    Workbook workbook = new XSSFWorkbook(inputStream);
    ExcelToHtmlConverter converter = new ExcelToHtmlConverter(DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument());
    converter.processWorkbook(workbook);

    // Get the HTML representation of the Excel file
    Document htmlDocument = converter.getDocument();
    StringWriter stringWriter = new StringWriter();
    Transformer transformer = TransformerFactory.newInstance().newTransformer();
    transformer.setOutputProperty(OutputKeys.INDENT, "yes");
    transformer.setOutputProperty(OutputKeys.METHOD, "html");
    transformer.transform(new DOMSource(htmlDocument), new StreamResult(stringWriter));
    String html = stringWriter.toString();

    // Add the HTML to the model and return the view name
    model.addAttribute("html", html);
    return "excel-preview";
}

在此示例中，我们使用Apache HttpClient库发送GET请求来下载Excel文件。然后，我们使用Apache POI将Excel文件转换为HTML，并使用Spring Boot将HTML呈现为视图。请注意，这只是一个简单的示例，并且您需要根据您的具体需求进行适当的调整。