Spring MVC 文件上傳下載完整配置與代碼實戰

Maven 依賴

<dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>5.3.30</version></dependency>
<dependency><groupId>commons-fileupload</groupId><artifactId>commons-fileupload</artifactId><version>1.4</version></dependency>
<dependency><groupId>commons-io</groupId><artifactId>commons-io</artifactId><version>2.11.0</version></dependency>

Spring 配置 spring-mvc.xml

<context:component-scan base-package="com.demo.controller"/>
<mvc:annotation-driven/>

<!-- 多部分解析器，支援文件上傳 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <property name="maxUploadSize" value="104857600"/> <!-- 100MB -->
    <property name="defaultEncoding" value="UTF-8"/>
</bean>

<!-- 視圖解析器 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/views/"/>
    <property name="suffix" value=".jsp"/>
</bean>

上傳頁面 upload.jsp

<form action="upload.do" method="post" enctype="multipart/form-data">
  選擇文件：<input type="file" name="file"/>
  <input type="submit" value="上傳"/>
</form>

Controller 實現

@Controller @RequestMapping("/file")
public class FileController {
    private static final String UPLOAD_DIR = "C:/uploads/";

    @PostMapping("/upload.do")
    public String upload(@RequestParam("file") MultipartFile file, RedirectAttributes ra) {
        if (file.isEmpty()) { ra.addFlashAttribute("msg", "請選擇文件"); return "redirect:upload.jsp"; }
        String original = file.getOriginalFilename();
        String saved = System.currentTimeMillis() + "_" + original; // 避免重名
        File dest = new File(UPLOAD_DIR, saved);
        try { file.transferTo(dest); ra.addFlashAttribute("msg", "上傳成功：" + saved); }
        catch (IOException e) { ra.addFlashAttribute("msg", "上傳失敗：" + e.getMessage()); }
        return "redirect:upload.jsp";
    }

    @GetMapping("/download.do")
    public ResponseEntity<byte[]> download(@RequestParam String fileName) throws IOException {
        File file = new File(UPLOAD_DIR, fileName);
        if (!file.exists()) throw new FileNotFoundException("文件不存在：" + fileName);

        HttpHeaders headers = new HttpHeaders();
        headers.setContentDispositionFormData("attachment", new String(fileName.getBytes("UTF-8"), "ISO-8859-1"));
        headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        return new ResponseEntity<>(FileUtils.readFileToByteArray(file), headers, HttpStatus.OK);
    }
}

關鍵點總結

• enctype="multipart/form-data" 表單屬性必加
• MultipartFile 參數名需與 <input name="file"> 一致
• transferTo() 直接寫磁盤，大文件高效；或用 file.getInputStream() 流式處理
• 下載時 ResponseEntity<byte[]> + Content-Disposition: attachment 觸發瀏覽器下載
• 中文文件名雙重編碼兼容 IE/現代瀏覽器
• 生產環境建議：文件存儲路徑配置化、異步上傳、病毒掃描、對象存儲（OSS/S3）替代本地磁盤