.NET 8实现大文件分片上传的高效方案汇总
作者:Microi风闲
在当今互联网应用中,大文件上传是一个常见需求,尤其是对于云存储、视频网站、企业文档管理系统等场景,传统的单次文件上传方式在面对大文件时往往会遇到网络不稳定、内存占用高、上传失败需重传整个文件等问题,本文将介绍如何在.NET 8中实现高效稳定的大文件分片上传方案
一、分片上传的优势
- 提高上传稳定性:单个分片上传失败只需重传该分片,而非整个文件
- 降低内存占用:每次只处理文件的一小部分,避免大文件完全加载到内存
- 支持断点续传:记录已上传分片,可从断点继续上传
- 并行上传:可同时上传多个分片,提高上传速度
- 进度显示:可精确显示上传进度,提升用户体验
二、.NET 8 分片上传实现
2.1 前端实现(JavaScript)
// 文件选择处理 document.getElementById('fileInput').addEventListener('change', async function(e) { const file = e.target.files[0]; if (!file) return; const chunkSize = 5 * 1024 * 1024; // 5MB分片 const totalChunks = Math.ceil(file.size / chunkSize); const fileId = generateFileId(file.name, file.size); // 生成唯一文件ID // 并行上传控制(限制同时上传的分片数) const parallelLimit = 3; let currentChunk = 0; let activeUploads = 0; let uploadedChunks = 0; while (currentChunk < totalChunks || activeUploads > 0) { if (activeUploads < parallelLimit && currentChunk < totalChunks) { activeUploads++; const chunkStart = currentChunk * chunkSize; const chunkEnd = Math.min(file.size, chunkStart + chunkSize); const chunk = file.slice(chunkStart, chunkEnd); try { await uploadChunk(fileId, currentChunk, chunk, totalChunks, file.name); uploadedChunks++; updateProgress(uploadedChunks / totalChunks * 100); } catch (error) { console.error(`分片 ${currentChunk} 上传失败:`, error); // 可加入重试逻辑 continue; // 重新尝试当前分片 } finally { activeUploads--; } currentChunk++; } else { // 等待有上传完成 await new Promise(resolve => setTimeout(resolve, 100)); } } // 所有分片上传完成,通知服务器合并 await notifyServerToMerge(fileId, file.name, totalChunks); console.log('文件上传完成'); }); async function uploadChunk(fileId, chunkNumber, chunkData, totalChunks, fileName) { const formData = new FormData(); formData.append('fileId', fileId); formData.append('chunkNumber', chunkNumber); formData.append('totalChunks', totalChunks); formData.append('fileName', fileName); formData.append('chunk', chunkData); const response = await fetch('/api/upload/chunk', { method: 'POST', body: formData }); if (!response.ok) { throw new Error('上传失败'); } } function updateProgress(percent) { console.log(`上传进度: ${percent.toFixed(2)}%`); // 更新UI进度条 document.getElementById('progressBar').style.width = `${percent}%`; }
2.2 后端实现(.NET 8 Web API)
控制器代码
[ApiController] [Route("api/[controller]")] public class UploadController : ControllerBase { private readonly IFileUploadService _uploadService; private readonly ILogger<UploadController> _logger; public UploadController(IFileUploadService uploadService, ILogger<UploadController> logger) { _uploadService = uploadService; _logger = logger; } [HttpPost("chunk")] [DisableRequestSizeLimit] // 禁用请求大小限制 public async Task<IActionResult> UploadChunk() { try { var form = await Request.ReadFormAsync(); var chunk = form.Files["chunk"]; if (chunk == null || chunk.Length == 0) return BadRequest("无效的分片数据"); var fileId = form["fileId"].ToString(); var chunkNumber = int.Parse(form["chunkNumber"].ToString()); var totalChunks = int.Parse(form["totalChunks"].ToString()); var fileName = form["fileName"].ToString(); await _uploadService.SaveChunkAsync(fileId, chunkNumber, totalChunks, fileName, chunk); return Ok(new { chunkNumber, fileId }); } catch (Exception ex) { _logger.LogError(ex, "分片上传失败"); return StatusCode(500, $"分片上传失败: {ex.Message}"); } } [HttpPost("merge")] public async Task<IActionResult> MergeChunks([FromBody] MergeRequest request) { try { var filePath = await _uploadService.MergeChunksAsync(request.FileId, request.FileName, request.TotalChunks); return Ok(new { filePath }); } catch (Exception ex) { _logger.LogError(ex, "分片合并失败"); return StatusCode(500, $"分片合并失败: {ex.Message}"); } } } public record MergeRequest(string FileId, string FileName, int TotalChunks);
文件上传服务实现
public interface IFileUploadService { Task SaveChunkAsync(string fileId, int chunkNumber, int totalChunks, string fileName, IFormFile chunk); Task<string> MergeChunksAsync(string fileId, string fileName, int totalChunks); } public class FileUploadService : IFileUploadService { private readonly string _uploadPath; private readonly ILogger<FileUploadService> _logger; public FileUploadService(IConfiguration configuration, ILogger<FileUploadService> logger) { _uploadPath = configuration["FileUpload:Path"] ?? Path.Combine(Directory.GetCurrentDirectory(), "Uploads"); _logger = logger; if (!Directory.Exists(_uploadPath)) { Directory.CreateDirectory(_uploadPath); } } public async Task SaveChunkAsync(string fileId, int chunkNumber, int totalChunks, string fileName, IFormFile chunk) { // 为每个文件创建临时目录 var tempDir = Path.Combine(_uploadPath, fileId); if (!Directory.Exists(tempDir)) { Directory.CreateDirectory(tempDir); } var chunkPath = Path.Combine(tempDir, $"{chunkNumber}.part"); // 使用文件流写入,避免内存占用过高 await using var stream = new FileStream(chunkPath, FileMode.Create); await chunk.CopyToAsync(stream); _logger.LogInformation("保存分片 {ChunkNumber}/{TotalChunks} 成功,文件ID: {FileId}", chunkNumber, totalChunks, fileId); } public async Task<string> MergeChunksAsync(string fileId, string fileName, int totalChunks) { var tempDir = Path.Combine(_uploadPath, fileId); if (!Directory.Exists(tempDir)) { throw new DirectoryNotFoundException($"临时目录不存在: {tempDir}"); } // 验证所有分片是否都存在 for (int i = 0; i < totalChunks; i++) { var chunkPath = Path.Combine(tempDir, $"{i}.part"); if (!System.IO.File.Exists(chunkPath)) { throw new FileNotFoundException($"分片 {i} 不存在", chunkPath); } } // 最终文件路径 var filePath = Path.Combine(_uploadPath, $"{fileId}_{fileName}"); // 合并分片 await using var outputStream = new FileStream(filePath, FileMode.Create); for (int i = 0; i < totalChunks; i++) { var chunkPath = Path.Combine(tempDir, $"{i}.part"); await using var chunkStream = new FileStream(chunkPath, FileMode.Open); await chunkStream.CopyToAsync(outputStream); _logger.LogDebug("已合并分片 {ChunkNumber}/{TotalChunks}", i, totalChunks); } // 删除临时分片 try { Directory.Delete(tempDir, true); _logger.LogInformation("文件合并完成,临时目录已删除: {TempDir}", tempDir); } catch (Exception ex) { _logger.LogWarning(ex, "删除临时目录失败: {TempDir}", tempDir); } return filePath; } }
2.3 配置与注册服务
在 Program.cs
中添加服务注册和配置:
var builder = WebApplication.CreateBuilder(args); // 添加服务 builder.Services.AddScoped<IFileUploadService, FileUploadService>(); // 配置上传路径 builder.Services.Configure<FileUploadOptions>(builder.Configuration.GetSection("FileUpload")); var app = builder.Build(); // 启用静态文件服务(如果需要下载) app.UseStaticFiles(new StaticFileOptions { FileProvider = new PhysicalFileProvider( Path.Combine(builder.Environment.ContentRootPath, "Uploads")), RequestPath = "/uploads" }); app.MapControllers(); app.Run();
在 appsettings.json
中添加配置:
{ "FileUpload": { "Path": "Uploads", "MaxFileSize": "1073741824" // 1GB } }
三、高级功能实现
3.1 断点续传
[HttpGet("check")] public IActionResult CheckChunks(string fileId, int totalChunks) { var tempDir = Path.Combine(_uploadPath, fileId); if (!Directory.Exists(tempDir)) { return Ok(new { uploadedChunks = Array.Empty<int>() }); } var uploaded = Directory.GetFiles(tempDir) .Select(f => Path.GetFileNameWithoutExtension(f)) .Where(f => int.TryParse(f, out _)) .Select(int.Parse) .ToArray(); return Ok(new { uploadedChunks = uploaded }); }
前端相应修改:
// 在上传前检查已上传的分片 const checkResponse = await fetch(`/api/upload/check?fileId=${fileId}&totalChunks=${totalChunks}`); const { uploadedChunks } = await checkResponse.json(); // 跳过已上传的分片 while (currentChunk < totalChunks) { if (uploadedChunks.includes(currentChunk)) { currentChunk++; uploadedChunks++; updateProgress(uploadedChunks / totalChunks * 100); continue; } // ...原有上传逻辑 }
3.2 文件校验(MD5/SHA)
public async Task<string> CalculateFileHash(string filePath) { await using var stream = System.IO.File.OpenRead(filePath); using var sha256 = SHA256.Create(); var hashBytes = await sha256.ComputeHashAsync(stream); return BitConverter.ToString(hashBytes).Replace("-", "").ToLowerInvariant(); } // 在上传完成后验证文件完整性 var calculatedHash = await CalculateFileHash(filePath); if (calculatedHash != expectedHash) { System.IO.File.Delete(filePath); throw new Exception("文件校验失败,可能在上传过程中损坏"); }
3.3 分片大小动态调整
根据网络状况动态调整分片大小:
// 动态调整分片大小 let chunkSize = 1 * 1024 * 1024; // 初始1MB let uploadSpeeds = []; async function uploadChunk(...) { const startTime = performance.now(); // ...上传逻辑 const endTime = performance.now(); const duration = (endTime - startTime) / 1000; // 秒 const speed = chunkData.size / duration; // bytes/s uploadSpeeds.push(speed); if (uploadSpeeds.length > 5) { uploadSpeeds.shift(); } const avgSpeed = uploadSpeeds.reduce((sum, val) => sum + val, 0) / uploadSpeeds.length; // 根据平均速度调整分片大小 (目标: 每个分片上传时间在5-15秒之间) const targetChunkTime = 10; // 10秒 chunkSize = Math.min( 50 * 1024 * 1024, // 最大50MB Math.max( 1 * 1024 * 1024, // 最小1MB Math.round(avgSpeed * targetChunkTime) ) ); }
四、性能优化与安全考虑
性能优化:
- 使用流式处理而非缓冲整个文件
- 并行上传控制
- 动态分片大小调整
- 内存管理优化
安全考虑:
- 文件类型检查
- 文件大小限制
- 病毒扫描集成
- 访问控制与权限验证
- 文件名校验与处理
错误处理:
- 网络中断重试机制
- 分片校验
- 超时处理
- 并发冲突处理
五、测试建议
单元测试:
- 分片保存与合并功能
- 文件校验逻辑
- 异常情况处理
集成测试:
- 完整上传流程
- 断点续传场景
- 网络不稳定的情况
性能测试:
- 不同文件大小的上传时间
- 并发上传测试
- 内存占用监控
六、总结
本文详细介绍了在.NET 8中实现大文件分片上传的完整方案,包括前端分片处理、后端分片接收与合并、断点续传等高级功能。该方案具有以下特点:
- 高效稳定,适合大文件上传场景
- 内存占用低,使用流式处理
- 支持断点续传,提升用户体验
- 可扩展性强,易于添加文件校验、病毒扫描等功能
通过合理配置和优化,该方案可以满足企业级应用对大文件上传的需求,为用户提供流畅可靠的上传体验。
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