基于Spring MVC的文件上传和下载实现方法

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="10000000"/>
</bean>

@Controller
public class FileUploadController {
    @RequestMapping(value = "/upload", method = RequestMethod.POST)
    public String handleFileUpload(@RequestParam("file") MultipartFile file, Model model) {
        if (!file.isEmpty()) {
            try {
                byte[] bytes = file.getBytes();
                // 处理上传文件
                model.addAttribute("message", "文件上传成功");
            } catch (IOException e) {
                e.printStackTrace();
                model.addAttribute("message", "文件上传失败");
            }
        } else {
            model.addAttribute("message", "请选择要上传的文件");
        }
        return "uploadResult";
    }
}

<form method="post" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file"/><br/><br/>
    <input type="submit" value="上传"/>
</form>

@Controller
public class FileUploadController {
    @RequestMapping(value = "/upload", method = RequestMethod.POST)
    public String handleFileUpload(HttpServletRequest request, Model model) {
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        MultipartFile file = multipartRequest.getFile("file");
        if (!file.isEmpty()) {
            try {
                byte[] bytes = file.getBytes();
                // 处理上传文件
                model.addAttribute("message", "文件上传成功");
            } catch (IOException e) {
                e.printStackTrace();
                model.addAttribute("message", "文件上传失败");
            }
        } else {
            model.addAttribute("message", "请选择要上传的文件");
        }
        return "uploadResult";
    }
}

<form method="post" action="/upload" enctype="multipart/form-data">
    <input type="file" name="file"/><br/><br/>
    <input type="submit" value="上传"/>
</form>

@Controller
public class FileDownloadController {
    @RequestMapping(value = "/download", method = RequestMethod.GET)
    public void downloadFile(HttpServletRequest request, HttpServletResponse response) {
        String fileName = "example.txt";
        String filePath = "/path/to/example.txt";
        File file = new File(filePath);
        if (file.exists()) {
            response.setContentType("application/octet-stream");
            response.setContentLength((int) file.length());
            response.setHeader("Content-Disposition", "attachment; filename="" + fileName + """);
            try {
                InputStream inputStream = new BufferedInputStream(new FileInputStream(file));
                OutputStream outputStream = new BufferedOutputStream(response.getOutputStream());
                byte[] buffer = new byte[1024];
                int bytesRead = 0;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                outputStream.flush();
                inputStream.close();
                outputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

<a href="/download" rel="external nofollow" >下载文件</a>