有时候，为了追求便利性，我们可能会让前端直接将文件上传到阿里云OSS，然后将URL提交给ASP.NET。然而，这种做法意味着前端需要拥有OSS的访问密钥，而将密钥存放在前端，无疑增加了被破解的风险。因此，最安全的做法仍然是由服务器端负责上传文件到OSS。

接下来，我将演示如何实现分块上传到服务器的过程，而且在这个过程中，服务器并不保存任何分块，而是直接将分块上传到OSS。

服务器端

---

asp.net 引用 nuget 包：
JMS.FileUploader.AspNetCore
Aliyun.OSS.SDK.NetCore

实现一个oss的 IUploadFilter ， 把接收到的分块数据，实时传到oss

    [UploadFilterDescription("Aliyun")]
    public class AliyunUploadFilter : IUploadFilter
    {
        const string BucketName = "<your-bucket-name>";
		const string OssEndpoint = "<your-oss-endpoint>";
		const string AccessKeyId = "<your-accessKeyId>";
		const string AccessKeySecret = "<your-accessKeySecret>";

        string _uploadId;
        string _ossUploadId;
        
        string _objectKey;
        OssClient _ossClient;
        public async Task OnUploadBeginAsync(HttpContext context, string uploadId, string fileName, long fileSize, int fileItemIndex)
        {
            _uploadId = uploadId;

            _objectKey = $"file{fileItemIndex}.zip";

            _ossClient = new OssClient(OssEndpoint , AccessKeyId , AccessKeySecret );

            var ret = _ossClient.InitiateMultipartUpload(new InitiateMultipartUploadRequest(BucketName, _objectKey));
            if (ret.HttpStatusCode != System.Net.HttpStatusCode.OK)
                throw new Exception(ret.HttpStatusCode.ToString());

            _ossUploadId = ret.UploadId;
        }

        public async Task OnReceivedAsync(HttpContext context, Stream inputStream, long position, int size)
        {

            var data = new byte[size];
            await inputStream.ReadAtLeastAsync(data, size);

            using var ms = new MemoryStream(data);

         
            var num = (int)(position / 102400) + 1;
            var ret = _ossClient.UploadPart(new UploadPartRequest(BucketName, _objectKey, _ossUploadId) { 
                InputStream = ms,
                
                PartSize = size,
                PartNumber = num
            });

            if (ret.HttpStatusCode != System.Net.HttpStatusCode.OK)
                throw new Exception(ret.HttpStatusCode.ToString());
        }


        public async Task<string> OnUploadCompletedAsync(HttpContext context)
        {

            for (int i = 0; i < 3; i++) // 如果发生错误，最多尝试3次
            {
                try
                {
                    // 列出所有分块。
                    var listPartsRequest = new ListPartsRequest(BucketName, _objectKey, _ossUploadId);
                    var partList = _ossClient.ListParts(listPartsRequest);

                    // 创建CompleteMultipartUploadRequest对象。
                    var completeRequest = new CompleteMultipartUploadRequest(BucketName, _objectKey, _ossUploadId);

                    // 设置分块列表。
                    foreach (var part in partList.Parts)
                    {
                        completeRequest.PartETags.Add(new PartETag(part.PartNumber, part.ETag));
                    }

                    // 完成上传。
                    var ret = _ossClient.CompleteMultipartUpload(completeRequest);


                    if (ret.HttpStatusCode != System.Net.HttpStatusCode.OK)
                        throw new Exception(ret.HttpStatusCode.ToString());

                    //设置访问权限
                    _ossClient.SetObjectAcl(BucketName, _objectKey, CannedAccessControlList.PublicRead);

                    //返回下载的url路径
                    return ret.Location;
                }
                catch (Exception)
                {
                    if (i == 2)
                    {
                        throw;
                    }
                    else
                    {
                        Thread.Sleep(3000);
                    }
                }
            }
            return null;
        }

        public void OnUploadError()
        {
           
        }

    }

然后注册这个 filter :

services.AddFileUploadFilter<AliyunUploadFilter>();

启用上传组件：

app.UseJmsFileUploader();

controller里面写一个最终的业务处理函数

    [ApiController]
    [Route("[controller]/[action]")]
    public class MainController : ControllerBase
    {

        [HttpPost]
        public string Test([FromBody] object body)
        {
            var customHeader = Request.Headers["Custom-Header"];

            //临时文件路径
            var filepath = Request.Headers["FilePath"];

            //文件名
            var filename = Request.Headers["Name"];
            return filepath + "\r\n" + filename + "\r\n" + customHeader;
        }
    }

前端

---

前端 import 模块：jms-uploader

    async function uploadToAliyun() {
        //自定义请求头
        var headers = function () {
            return { "Custom-Header": "test" };
        };

        //提交的body
        var dataBody = {
            name: "abc"
        };

        var uploader = new JmsUploader("http://localhost:5200/Main/Test", [document.querySelector("#file1").files, document.querySelector("#file2").files], headers, dataBody);

        uploader.setPartSize(1024*300);//设置分块大小300K
        uploader.setUploadFilter("Aliyun");//设置服务器使用哪个upload filter

        uploader.onUploading = function (percent, uploadedSize, totalSize) {
            document.querySelector("#info").innerHTML = percent + "% " + uploadedSize + "," + totalSize;
        };

        try {
            var ret = await uploader.upload();
            alert(ret);
        } catch (e) {
            alert("错误：" + JSON.stringify(e));
        }
    }

html

<body>
    <input id="file1" multiple type="file" />
    <input id="file2" multiple type="file" />
    <button onclick="uploadToAliyun()">
        upload to aliyun oss
    </button>
    <div id="info"></div>
</body>