前言：
大文件传输一直是技术上的一大难点。文件过大时，一些性提交所有的内容进内存是不现实的。大文件带来问题还有是否支持断点传输和多文件同时传输。
本文以resumableJs为例，介绍了如何在ASP.NET中实现大文件传输。同时本文利用了Html5的新特性：支持拖拽。
本文的主要技术点在于：如何接收resumableJs的传送内容（官网不太清楚）和如何合并文件，难度并不高。如果要改为MVC中的Controller处理文件传输，方法也大同小异。
注：原博客中，此文章在原站点个人代码备份所用，注释不多，如有不懂，请在评论中给出。
效果：
ASPX File:
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Resumable.js Test</title>
</head>
<body>
<form id="form1" runat="server">
<div id="container" style="width:300px;height:200px;background-color:lightgray"> </div>
</form>
<span id="info">welcome</span>
<script src="scripts/resumable.js" type="text/javascript"></script>
<script type="text/javascript">
var showInfo = function (msg) {
document.getElementById("info").innerHTML = msg;
}
showInfo("Test begin");
var r = new Resumable({
target: 'FileHandler.ashx',
});
r.assignBrowse(document.getElementById('container'));
r.assignDrop(document.getElementById('container'));
if (!r.support) showInfo("not support");
r.on('fileAdded', function (file, event) {
r.upload();
});
r.on('filesAdded', function (array) {
for (var i = 0; i < array.length; i++) {
var html = document.getElementById("info").innerHTML;
html += "<br>"+array[i].name;
}
});
r.on('uploadStart', function () {
showInfo('start');
});
r.on('complete', function () {
r.files.pop();
//if want to upload one file multiple times, you should remove it from r.files after completing.
//pop后，才可再次重新拖拽上传此文件。此机制可避免一次上传多个文件时重复添加，但拖拽上传时不用检测。
});
r.on('progress', function (e) {
showInfo(r.progress());
});
</script>
</body>
</html>
FileHandler
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Web;
namespace UploadTest
{
/// <summary>
/// Summary description for FileHandler
/// </summary>
public class FileHandler : IHttpHandler
{
string _tempFolder;
object _lock = new object();
public void ProcessRequest(HttpContext context)
{
_tempFolder = context.Server.MapPath("~/temp");
var method = context.Request.HttpMethod;
if (method.Equals("GET"))
{
HandleGet(context);
}
if (method.Equals("POST"))
{
HandlePost(context);
}
}
private void HandlePost(HttpContext context)
{
var queryString = context.Request.Form;
if (queryString.Count == 0) return;
try
{
// Read parameters
var uploadToken = queryString.Get("upload_Token");
int resumableChunkNumber = int.Parse(queryString.Get("resumableChunkNumber"));
var resumableTotalChunks = int.Parse(queryString.Get("resumableTotalChunks"));
var resumableTotalSize = long.Parse(queryString.Get("resumableTotalSize"));
var resumableFilename = queryString.Get("resumableFilename");
// Save File
if (context.Request.Files.Count == 0)
{
context.Response.StatusCode = (int)System.Net.HttpStatusCode.InternalServerError;
}
else
{
var filePath = string.Format("{0}/{1}/{1}.part{2}", _tempFolder, resumableFilename, resumableChunkNumber.ToString("0000"));
var directory = Path.GetDirectoryName(filePath);
if (File.Exists(directory))
{
File.Delete(directory);
}
if (!Directory.Exists(directory))
{
Directory.CreateDirectory(directory);
}
if (!System.IO.File.Exists(filePath))
{
context.Request.Files[0].SaveAs(filePath);
}
if (IsCompleted(directory,resumableTotalChunks,resumableTotalSize))
{
MergeFiles(directory);
}
}
}
catch (Exception exception)
{
throw exception;
}
}
private void HandleGet(HttpContext context)
{
var queryString = context.Request.QueryString;
if (queryString.Count == 0) return;
try
{
// Read parameters
var uploadToken = queryString.Get("upload_Token");
int resumableChunkNumber = int.Parse(queryString.Get("resumableChunkNumber"));
var resumableFilename = queryString.Get("resumableFilename");
var resumableChunkSize = long.Parse(queryString.Get("resumableChunkSize"));
var filePath = string.Format("{0}/{1}/{1}.part{2}", _tempFolder,
resumableFilename, resumableChunkNumber.ToString("0000"));
// Check for existance and chunksize
if (System.IO.File.Exists(filePath) && new FileInfo(filePath).Length == resumableChunkSize)
{
context.Response.Status = "200 OK";
context.Response.StatusCode = 200;
}
else
{
context.Response.Status = "404 Not Found";
context.Response.StatusCode = 404;
}
}
catch (Exception exception)
{
throw exception;
}
}
private bool IsCompleted(string directory,int numChunks, long totalSize )
{
var physicalFolder = Path.Combine(_tempFolder, directory);
var files = Directory.GetFiles(physicalFolder);
//numbers
if (files.Length != numChunks)
return false;
//files all exisit
var fileName = Path.GetFileName(directory);
for (int i = 1; i <= numChunks; i++)
{
var filePath = string.Format("{0}/{1}.part{2}", directory, fileName, i.ToString("0000"));
if (!File.Exists(filePath))
{
return false;
}
}
//size
long tmpSize = 0;
foreach (var file in files)
{
tmpSize += new FileInfo(file).Length;
}
return totalSize==tmpSize;
}
private void MergeFiles(string directoryPath)
{
lock (_lock)
{
if (Directory.Exists(directoryPath))
{
var fileName = Path.GetFileName(directoryPath);
var folder = Path.GetDirectoryName(directoryPath);
var tempPath = Path.Combine(directoryPath + ".tmp");
var files = Directory.GetFiles(directoryPath);
files = files.OrderBy(f => f).ToArray();
FileStream wholeStream = new FileStream(tempPath, FileMode.Append, FileAccess.Write);
for(int i=0;i<files.Length;i++)
{
FileStream parcialStream = new FileStream(files[i], FileMode.Open);
BinaryReader parcialReader = new BinaryReader(parcialStream);
byte[] buffer = new byte[parcialStream.Length];
buffer = parcialReader.ReadBytes((int)parcialStream.Length);
BinaryWriter parcialWriter = new BinaryWriter(wholeStream);
parcialWriter.Write(buffer);
parcialStream.Close();
}
wholeStream.Close();
Directory.Delete(directoryPath,true);
File.Move(tempPath, directoryPath);
}
}
}
public bool IsReusable
{
get
{
return false;
}
}
}
}
附录：
1 技术难点
a. 文件过大。修改webconfig无用。
b. 断点续传。
c. 多文件上传。
2 resumable.js
API: http://www.resumablejs.com/
工作流程：
拖文件至DIV -> 开始上传，uploadStart -> 反复触发progress事件 -> compete
主要参数：
Get:
resumableChunkNumber=1&
resumableChunkSize=1048576&
resumableCurrentChunkSize=1048576&
resumableTotalSize=27778318&
resumableType=&
resumableIdentifier=27778318-Samples7z&
resumableFilename=Samples.7z&
resumableRelativePath=Samples.7z&
resumableTotalChunks=26
Post:
—————————–111061030216033
Content-Disposition: form-data; name=”resumableChunkNumber”
140
—————————–111061030216033
Content-Disposition: form-data; name=”resumableChunkSize”
1048576
—————————–111061030216033
Content-Disposition: form-data; name=”resumableCurrentChunkSize”
1048576
—————————–111061030216033
Content-Disposition: form-data; name=”resumableTotalSize”
171309601
—————————–111061030216033
Content-Disposition: form-data; name=”resumableType”
—————————–111061030216033
Content-Disposition: form-data; name=”resumableIdentifier”
171309601-sample7z
—————————–111061030216033
Content-Disposition: form-data; name=”resumableFilename”
sample.7z
—————————–111061030216033
Content-Disposition: form-data; name=”resumableRelativePath”
sample.7z
—————————–111061030216033
Content-Disposition: form-data; name=”resumableTotalChunks”
163
—————————–111061030216033
Content-Disposition: form-data; name=”file”; filename=”blob”
Content-Type: application/octet-stream
XXXCONTENT
—————————–309022088923579–