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HttpHandler to look for cached assets, and if they exist, send them
compressed with long-lived HTTP cache headers.
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using System;
using System.Collections.Generic;
using System.IO.Compression;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using System.Web;
namespace WebCache
{
public class WebCacheHttpHandler : IHttpHandler
{
public bool IsReusable { get { return false; } }
public void ProcessRequest(HttpContext context)
{
var response = context.Response;
var path = context.Request.Path;
var cachedAsset = WebCache.Bundles
.SelectMany(b => b.Value)
.SingleOrDefault(a => a.CachedVirtualPath == path);
if (cachedAsset == null)
{
response.StatusCode = (int)HttpStatusCode.NotFound;
response.End();
return;
}
var file = cachedAsset.File;
if (!cachedAsset.File.Exists)
{
response.StatusCode = (int)HttpStatusCode.NotFound;
response.End();
return;
}
SetHeaders(response);
response.ContentType = GetContentType(file.Extension);
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TODO: Add support for content negotiation
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response.Filter = new GZipStream(context.Response.Filter, CompressionMode.Compress);
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TransmitFile() is awesome and doesn't buffer the file in memory. This is the reason cached assets are written to disk.
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response.TransmitFile(file.FullPath);
}
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Based on Google-suggested best practice.
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private void SetHeaders(HttpResponse response)
{
var now = DateTime.UtcNow;
var expires = now.AddYears(1);
var lastModified = now.AddMonths(-1);
response.ClearHeaders();
response.AppendHeader("Content-Encoding", "gzip");
response.AppendHeader("Vary", "Accept-Encoding");
response.AppendHeader("Last-Modified", lastModified.ToHttpDate());
response.AppendHeader("Expires", expires.ToHttpDate());
response.AppendHeader("Cache-Control", "public");
}
private string GetContentType(string fileExtension)
{
switch (fileExtension)
{
case ".css":
return "text/css";
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There are two other obsoleted content types for JavaScript.
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case ".js":
return "application/javascript";
default:
return "application/unknown";
}
}
}
}
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