SpringBoot实现文件上传与下载的完整指南(单文件、多文件、大文件分片)

spring:
  servlet:
    multipart:
      enabled: true
      max-file-size: 10MB        # 单个文件最大
      max-request-size: 50MB     # 总请求最大
      file-size-threshold: 2KB   # 文件大小阈值
      location: /tmp

@Configuration
@ConfigurationProperties(prefix = "file")
@Data
public class FileStorageConfig {
    private String uploadDir = "/data/uploads";
    private String downloadUrl = "/files";
}

@RestController
@RequestMapping("/file")
public class FileController {

    @Autowired
    private FileStorageConfig config;

    @PostMapping("/upload")
    public ResultVO<String> upload(@RequestParam("file") MultipartFile file) {
        if (file.isEmpty()) {
            return ResultVO.error(400, "请选择文件");
        }

        try {
            // 1. 生成存储文件名
            String originalName = file.getOriginalFilename();
            String ext = originalName.substring(originalName.lastIndexOf("."));
            String saveName = IdUtil.simpleUUID() + ext;

            // 2. 按日期分目录
            String datePath = DateUtil.today();
            File dir = new File(config.getUploadDir(), datePath);
            if (!dir.exists()) dir.mkdirs();

            // 3. 保存文件
            File dest = new File(dir, saveName);
            file.transferTo(dest);

            // 4. 返回可访问路径
            String url = config.getDownloadUrl() + "/" + datePath + "/" + saveName;
            return ResultVO.success(url);
        } catch (IOException e) {
            return ResultVO.error(500, "上传失败");
        }
    }
}

@PostMapping("/uploads")
public ResultVO<List<String>> uploadMultiple(
        @RequestParam("files") MultipartFile[] files) {
    List<String> urls = new ArrayList<>();
    for (MultipartFile file : files) {
        // 逐个上传
        urls.add(upload(file));
    }
    return ResultVO.success(urls);
}

@GetMapping("/download/{datePath}/{fileName}")
public void download(@PathVariable String datePath,
                     @PathVariable String fileName,
                     HttpServletResponse response) {
    File file = new File(config.getUploadDir(), datePath + "/" + fileName);
    if (!file.exists()) {
        response.setStatus(404);
        return;
    }
    response.setContentType("application/octet-stream");
    response.setHeader("Content-Disposition",
        "attachment;filename=" + URLEncoder.encode(fileName, "UTF-8"));

    Files.copy(file.toPath(), response.getOutputStream());
}