一、上传大文件的方式
上传大文件就需要一段一段的上传，主要是先在客户端获取文件的大小，例如想一次传256kb，那就按照256kb分割。分割后又两种上传方式。
（1）逐个数据段读取，然后调用API上传，把数据追加到文件上。上传完这一段，接着传下一段，直到上传完毕。
（2）方式与（1）类似，只是可以好几段可以并行上传，上传后，会把每段按照索引命名，在服务器上保存成临时文件。判断都上传完毕后，再调用合并命令，把这些小的碎文件，合并成大的目标文件。
我一般喜欢用第一种方式，主要是因为简单明了。缺点就是，因为必须等上一段完成后，再传下一段，所以无法并行上传，导致速度会受到影响。但我参与的项目基本上都是在局域网运行并且使用人数有限，所以这种传大文件的方式是可以满足系统要求。
二、上传大文件API实现
下面的实现用到了定义的AttachedFileEntity和HttpClientEx，这两个类的定义可参考 005 Controller上传小文件。
分三步，开始上传、循环上传二进制段、结束上传。
开始上传API的目的是为了获取文件在服务器上的存储路径，代码如下。
/// <summary>
/// 堆代码 duidaima.com
/// 开始大上传文件
/// </summary>
/// <returns></returns>
[HttpPost]
[Route("StartUploadBigFile")]
public IActionResult StartUploadBigFile(AttachedFileEntity pEntity, string pFileEx)
{
string myServerFilePath = DateTime.Now.ToString("yyyy_MM_dd") + "\\" + Guid.NewGuid().ToString() + pFileEx;
pEntity.ServerPath = myServerFilePath;
return this.Ok(pEntity);
}
分段上传文件，接收到后，追加到现有的文件上。
/// <summary>
/// 上传大文件
/// </summary>
/// <param name="pServerPath"></param>
/// <returns></returns>
[HttpPost]
[Route("UploadBigFile")]
[DisableRequestSizeLimit]
public IActionResult UploadBigFile(string pServerPath)
{
var myFile = Request.Form.Files[0];
//创建目录
string myFullServerPath = AppDomain.CurrentDomain.BaseDirectory + "\\Files\\" + pServerPath;
string myFullFolder = Path.GetDirectoryName(myFullServerPath)!;
if (Directory.Exists(myFullFolder) == false)
{
Directory.CreateDirectory(myFullFolder);
}
//写入文件
Stream? myStream = null;
FileStream? myFileStream = null;
BinaryWriter? myBinaryWriter = null;
try
{
myStream = myFile.OpenReadStream();
byte[] myBytes = new byte[myStream.Length];
myStream.Read(myBytes, 0, myBytes.Length);
myStream.Seek(0, SeekOrigin.Begin);
myFileStream = new FileStream(myFullServerPath, FileMode.Append);
myBinaryWriter = new BinaryWriter(myFileStream);
myBinaryWriter.Write(myBytes);
}
catch (Exception ex)
{
return this.BadRequest("上传大文件失败," + ex.Message);
}
finally
{
myBinaryWriter?.Close();
myFileStream?.Close();
myStream?.Close();
}
return this.Ok();
}
最后，结束上传，把文件的信息记录到数据库中。
/// <summary>
/// 结束上传大文件
/// </summary>
/// <returns></returns>
[HttpPost]
[Route("FinishUploadBigFile")]
public IActionResult FinishUploadBigFile(AttachedFileEntity pEntity)
{
if (string.IsNullOrEmpty(pEntity.GUID))
{
pEntity.GUID = Guid.NewGuid().ToString();
}
//记录到数据库中
//代码略
return this.Ok(pEntity);
}
三、客户端调用
客户端如果用的C#，代码中没有加入进度信息，进度信息可以传入一个ProcessInfo对象，传一段数据后，就更新下进度信息。
调用的代码入下所示。
private void Init_BigFileUpLoad_UIs()
{
this.UI_BigFile_Button.Click += (x, y) =>
{
var myOpenFileDialog = new OpenFileDialog
{
Filter = ".*|*.*"
};
var myIsOK = myOpenFileDialog.ShowDialog();
if (myIsOK != true)
{
return;
}
this.UI_BigFile_TextBox.Text = myOpenFileDialog.FileName;
};
this.UI_BigFileUpLoad_Button.Click += async (x, y) =>
{
var myFilePath = this.UI_BigFile_TextBox.Text.Trim();
if (myFilePath.Length == 0)
{
MessageBox.Show("请选择一个文件。");
return;
}
if (File.Exists(myFilePath) == false)
{
MessageBox.Show("文件不存在，请重新选择。");
return;
}
//定义AttachedFileEntity
var myFileEntity = new AttachedFileEntity()
{
GUID = Guid.NewGuid().ToString(),
Name = "用户头像",
KeyWord = "UserProfilePhoto",
Description = "",
EntityGUID = "AAAA"
};
//打开上传的文件
var myFileStream = new FileStream(myFilePath, FileMode.Open);
myFileEntity.FileSize = (int)myFileStream.Length;
var myFileName = Path.GetFileName(myFilePath);
//每次上传256kb
int myChunkSize = 1024 * 256;
int myChunkCount = (int)Math.Ceiling(myFileStream.Length / (double)myChunkSize);
//调用开始上传
var myHttpClient = new HttpClient();
var myHttpClientEx = new HttpClientEx(myHttpClient)
{
Url = "http://localhost:5000/api/AttachedFile/StartUploadBigFile",
HttpContent = JsonContent.Create(myFileEntity)
};
myHttpClientEx.ParameterDictionary.Add("pFileEx", Path.GetExtension(myFileName));
await myHttpClientEx.PostAsync();
if (myHttpClientEx.IsSuccess == false)
{
myFileStream.Close();
MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);
return;
}
myFileEntity = myHttpClientEx.GetResponseObject<AttachedFileEntity>();
if (myFileEntity == null)
{
myFileStream.Close();
MessageBox.Show("上传文件失败，返回的AttachedFileEntity为null。");
return;
}
//循环上传文件
for (int i = 0; i < myChunkCount; i++)
{
//组织数据
int myByteArraySize = myChunkSize;
if (i == myChunkCount - 1)
{
myByteArraySize = (int)(myFileStream.Length % myChunkSize);
}
byte[] myBytes = new byte[myByteArraySize];
myFileStream.Position = myChunkSize * i;
myFileStream.Read(myBytes, 0, myBytes.Length);
var myMemoryStream = new MemoryStream(myBytes);
//请求服务
myHttpClientEx = new HttpClientEx(myHttpClient)
{
Url = "http://localhost:5000/api/AttachedFile/UploadBigFile",
HttpContent = new MultipartFormDataContent
{
{new StreamContent(myMemoryStream),"pFile",myFileName}
}
};
myHttpClientEx.ParameterDictionary.Add("pServerPath", myFileEntity!.ServerPath);
await myHttpClientEx.PostAsync();
//解析结果
if (myHttpClientEx.IsSuccess == false)
{
myFileStream.Close();
MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);
return;
}
}
//结束上传
myHttpClientEx = new HttpClientEx(myHttpClient)
{
Url = "http://localhost:5000/api/AttachedFile/FinishUploadBigFile",
HttpContent = JsonContent.Create<AttachedFileEntity>(myFileEntity)
};
await myHttpClientEx.PostAsync();
if (myHttpClientEx.IsSuccess == false)
{
myFileStream.Close();
MessageBox.Show("上传文件失败，" + myHttpClientEx.ResponseContenString);
return;
}
myFileStream.Close();
myFileEntity = myHttpClientEx.GetResponseObject<AttachedFileEntity>();
var myEntityJosnString = JsonSerializer.Serialize<AttachedFileEntity>(myFileEntity);
MessageBox.Show(myEntityJosnString);
};
}
如果客户端是js，代码如下。
on(myButton, "change", function (e) {
var myFileReader = new FileReader();
var myFileName = "";
myFileReader.onloadend = function () {
var myFileResult = myFileReader.result;
var myFileLength = myFileResult.byteLength;
var myPerLength = 1024 * 256;
var myCount = Math.ceil(myFileLength / myPerLength);
var myFileEntity = new Object()
{
ServerPath: ""
};
//调用开始上传StartUploadBigFile，具体代码略。
var myK = 0;
Upload();
function Upload() {
var myByteArray = myFileResult.slice(myPerLength * myK, myPerLength * (myK + 1));
var myBlob = new Blob([myByteArray]);
var myFile = new File([myBlob], myFileName);
var myFormData = new FormData();
myFormData.append("file", myFile)
request.post(myUrl + "?pServerFile=" + myFileEntity.ServerPath +, {
data: myFormData
}).then(function (data) {
myFileEntity = json.parse(data);
myK++;
if (myK < myCount) {
Upload();
}
else {
alert("上传大文件结束。");
alert(json.stringify(myFileEntity));
//结束，post FinishUploadBigFile
}
}, function (err) {
alert(err);
return;
});
}
}
myFileName = this.files[0].name;
myFileReader.readAsArrayBuffer(this.files[0]);
});
Js代码没有实际测试，只是一个思路。
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