SpringBoot中实现大文件分片下载和断点续传功能的完整指南

@GetMapping("/download")
public ResponseEntity<InputStreamResource> downloadFile(
    @RequestHeader(value = "Range", required = false) String rangeHeader,
    HttpServletRequest request) throws IOException {
    
    // 获取文件信息
    File file = new File("/path/to/largefile.zip");
    long fileSize = file.length();
    
    // 解析Range头
    long start = 0, end = fileSize - 1;
    if (rangeHeader != null) {
        String[] ranges = rangeHeader.replace("bytes=", "").split("-");
        start = Long.parseLong(ranges[0]);
        if (ranges.length > 1) {
            end = Long.parseLong(ranges[1]);
        }
    }
    
    // 校验范围合法性
    if (start >= fileSize || end >= fileSize || start > end) {
        return ResponseEntity.status(HttpStatus.REQUESTED_RANGE_NOT_SATISFIABLE)
                .header("Content-Range", "bytes */" + fileSize)
                .build();
    }
    
    // 设置响应头
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    headers.setContentLength(end - start + 1);
    headers.setHeader("Content-Range", "bytes " + start + "-" + end + "/" + fileSize);
    headers.setHeader("Accept-Ranges", "bytes");
    
    // 返回分片数据流
    try (InputStream is = new FileInputStream(file);
         InputStreamResource resource = new InputStreamResource(is)) {
        is.skip(start);
        return new ResponseEntity<>(resource, headers, HttpStatus.PARTIAL_CONTENT);
    }
}

// 分片下载逻辑
async function downloadFileWithResume(fileId, fileName) {
  const CHUNK_SIZE = 5 * 1024 * 1024; // 5MB
  let downloadedBytes = 0;
  
  // 获取文件总大小
  const response = await fetch(`/api/files/${fileId}/size`);
  const totalSize = parseInt(await response.text());
  
  // 检查本地是否有已下载部分
  const tempFile = await checkLocalProgress(fileName);
  if (tempFile) {
    downloadedBytes = tempFile.size;
  }
  
  // 分片下载
  while (downloadedBytes < totalSize) {
    const end = Math.min(downloadedBytes + CHUNK_SIZE - 1, totalSize - 1);
    const response = await fetch(`/api/files/${fileId}/download`, {
      headers: { Range: `bytes=${downloadedBytes}-${end}` }
    });
    
    if (!response.ok) throw new Error("下载失败");
    
    const blob = await response.blob();
    await appendToFile(tempFile, blob);
    downloadedBytes += blob.size;
    
    // 更新进度
    updateProgress(downloadedBytes / totalSize);
  }
  
  // 完成后重命名文件
  await renameTempFile(tempFile, fileName);
}

// 检查本地进度
async function checkLocalProgress(fileName) {
  const tempPath = `/temp/${fileName}.part`;
  return new Promise(resolve => {
    fs.stat(tempPath, (err, stats) => {
      if (err) resolve(null);
      else resolve(fs.createWriteStream(tempPath, { flags: 'a' }));
    });
  });
}

@Service
public class DownloadService {
    private final ExecutorService executor = Executors.newFixedThreadPool(10);
    
    public void downloadChunk(String fileId, long start, long end) {
        executor.submit(() -> {
            // 分片下载逻辑
        });
    }
}

@Autowired
private RedisTemplate<String, String> redisTemplate;

public void saveProgress(String fileId, long downloadedBytes) {
    redisTemplate.opsForValue().set(fileId, String.valueOf(downloadedBytes));
}

curl -H "Range: bytes=0-999" http://localhost:8080/download