本文讲解 Spring Boot 文件上传下载包括 Multipart、分片上传、断点续传、秒传、限制配置和阿里云 OSS 集成。正文1. 基础上传java复制下载PostMapping(/upload) public ResultString upload(RequestParam(file) MultipartFile file) throws IOException { String filename UUID.randomUUID() _ file.getOriginalFilename(); Path target Path.of(/data/upload, filename); Files.createDirectories(target.getParent()); file.transferTo(target); return Result.success(filename); }2. 配置限制yaml复制下载spring: servlet: multipart: max-file-size: 100MB max-request-size: 200MB enabled: true3. 下载java复制下载GetMapping(/download/{name}) public ResponseEntityResource download(PathVariable String name) { Path path Path.of(/data/upload, name); Resource resource new FileSystemResource(path); return ResponseEntity.ok() .header(HttpHeaders.CONTENT_DISPOSITION, attachment; filename\ name \) .contentType(MediaType.APPLICATION_OCTET_STREAM) .body(resource); }4. 分片上传前端将文件切成固定大小分片逐片上传。java复制下载PostMapping(/chunk) public ResultVoid uploadChunk( RequestParam String fileId, RequestParam int chunkIndex, RequestParam MultipartFile chunk) throws IOException { Path dir Path.of(/data/chunks, fileId); Files.createDirectories(dir); chunk.transferTo(dir.resolve(String.valueOf(chunkIndex))); return Result.success(null); } PostMapping(/merge) public ResultString merge(RequestParam String fileId, RequestParam int total, RequestParam String filename) throws IOException { Path dir Path.of(/data/chunks, fileId); Path target Path.of(/data/upload, filename); try (OutputStream out Files.newOutputStream(target)) { for (int i 0; i total; i) { Files.copy(dir.resolve(String.valueOf(i)), out); } } deleteDir(dir); return Result.success(filename); }5. 断点续传上传前查询已上传分片java复制下载GetMapping(/chunks/{fileId}) public ResultListInteger uploadedChunks(PathVariable String fileId) throws IOException { Path dir Path.of(/data/chunks, fileId); if (!Files.exists(dir)) return Result.success(List.of()); try (StreamPath stream Files.list(dir)) { ListInteger list stream .map(p - Integer.parseInt(p.getFileName().toString())) .sorted() .toList(); return Result.success(list); } }前端跳过已上传分片。6. 秒传基于文件 MD5 判断是否已存在java复制下载PostMapping(/check) public ResultString check(RequestParam String md5) { String existing fileHashService.findByMd5(md5); return Result.success(existing); }7. 阿里云 OSS 集成xml复制下载运行dependency groupIdcom.aliyun.oss/groupId artifactIdaliyun-sdk-oss/artifactId version3.17.4/version /dependencyjava复制下载OSS ossClient new OSSClientBuilder().build(endpoint, ak, sk); ossClient.putObject(bucket, key, inputStream); String url https:// bucket . endpoint / key;分片上传用MultipartUpload。8. 安全考虑文件类型白名单。文件大小限制。文件名防路径穿越。存储目录不可执行。病毒扫描。9. 常见坑大文件内存溢出。临时文件未清理。并发上传同名文件冲突。OSS 签名过期。10. 总结文件上传下载要处理大文件、分片、断点续传和秒传。生产建议直接使用 OSS/S3本地只做转发和校验