using System.IO;namespace ND.Race.Compressor
{/// <summary>/// 压缩器接口/// </summary>public interface ICompressor{string EncodingName { get; }bool CanHandle(string acceptEncoding);void Compress(string content, Stream targetStream);}
}GZip压缩器实现这个接口。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29using System.IO;
using System.IO.Compression;
using System.Text;namespace ND.Race.Compressor
{public sealed class GZipCompressor : ICompressor{public string EncodingName{get { return "gzip"; }}public bool CanHandle(string acceptEncoding){return !string.IsNullOrEmpty(acceptEncoding) &&acceptEncoding.Contains("gzip");}public void Compress(string content, Stream targetStream){using (var writer = new GZipStream(targetStream, CompressionMode.Compress)){var bytes = Encoding.UTF8.GetBytes(content);writer.Write(bytes, 0, bytes.Length);}}}
}

using System.IO;
using System.IO.Compression;
using System.Text;namespace ND.Race.Compressor
{public sealed class DeflateCompressor : ICompressor{public string EncodingName{get { return "deflate"; }}public bool CanHandle(string acceptEncoding){return !string.IsNullOrEmpty(acceptEncoding) &&acceptEncoding.Contains("deflate");}public void Compress(string content, Stream targetStream){using (var writer = new DeflateStream(targetStream, CompressionMode.Compress)){var bytes = Encoding.UTF8.GetBytes(content);writer.Write(bytes, 0, bytes.Length);}}}
}

using System.IO;
using System.Text;namespace ND.Race.Compressor
{public sealed class NullCompressor : ICompressor{public string EncodingName{get { return "utf-8"; }}public bool CanHandle(string acceptEncoding){return true;}public void Compress(string content, Stream targetStream){using (targetStream){var bytes = Encoding.UTF8.GetBytes(content);targetStream.Write(bytes, 0, bytes.Length);}}}
}

public class QuestionCacheHandler : IHttpHandler
{#region 静态变量/// <summary>/// 资源过期时间/// </summary>private static readonly int durationInDays = 30;/// <summary>/// 流压缩接口/// </summary>private static readonly ICompressor[] Compressors = {new GZipCompressor(),new DeflateCompressor(),new NullCompressor()};#endregion#region 私有变量/// <summary>/// 内存流压缩类/// </summary>private ICompressor compressor;/// <summary>/// ETAG/// </summary>private string eTagCacheKey;/// <summary>/// 竞赛场次Id/// </summary>private long raceId;#endregionpublic void ProcessRequest(HttpContext context){if (context == null) return;long.TryParse(context.Request.QueryString["raceId"], out raceId);if (raceId == 0) return;       var acceptEncoding = context.Request.Headers["Accept-Encoding"];compressor = Compressors.First(o => o.CanHandle(acceptEncoding));eTagCacheKey = string.Concat(raceId, "/etag");if (IsInBrowserCache(context, eTagCacheKey)) return;SendOutputToClient(context, true, eTagCacheKey);}/// <summary>/// 发送内容到客户端/// </summary>/// <param name="context"></param>/// <param name="insertCacheHeaders"></param>/// <param name="etag"></param>private void SendOutputToClient(HttpContext context, bool insertCacheHeaders, string etag){string content = "";MemoryStream memoryStream = new MemoryStream();compressor.Compress(content, memoryStream);byte[] bytes = memoryStream.ToArray();HttpResponse response = context.Response;if (insertCacheHeaders){HttpCachePolicy cache = context.Response.Cache;cache.SetETag(etag);cache.SetOmitVaryStar(true);cache.SetMaxAge(TimeSpan.FromDays(durationInDays));cache.SetLastModified(DateTime.Now);cache.SetExpires(DateTime.Now.AddDays(durationInDays)); // HTTP 1.0 的浏览器使用过期时间cache.SetValidUntilExpires(true);cache.SetCacheability(HttpCacheability.Public);cache.SetRevalidation(HttpCacheRevalidation.AllCaches);cache.VaryByHeaders["Accept-Encoding"] = true;}response.AppendHeader("Content-Length", bytes.Length.ToString(System.Globalization.CultureInfo.InvariantCulture));response.ContentType = "text/plain";response.ContentType = "application/x-javascript";response.AppendHeader("Content-Encoding", compressor.EncodingName);if (bytes.Length > 0)response.OutputStream.Write(bytes, 0, bytes.Length);if (response.IsClientConnected)response.Flush();}/// <summary>/// 是否浏览器已经缓存/// </summary>/// <param name="context"></param>/// <param name="etag"></param>/// <returns></returns>private bool IsInBrowserCache(HttpContext context, string etag){string incomingEtag = context.Request.Headers["If-None-Match"];if (String.Equals(incomingEtag, etag, StringComparison.Ordinal)){context.Response.Cache.SetETag(etag);context.Response.AppendHeader("Content-Length", "0");context.Response.StatusCode = (int)System.Net.HttpStatusCode.NotModified;context.Response.End();return true;}return false;}public bool IsReusable{get{return false;}}
}