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再写完缓存篇第一回之后，得到了很多朋友的好评和来信，所以，决定加快步伐，尽快把剩下的文章写完，本篇是第三回，主要介绍使用HttpModule实现的文件级缓存，在看本文之前，大家需要限度HttpModule有一个了解，可以先看我的这篇文章《开发人员应该对IIS理论层的知识了解的多一些~第四讲 HttpModule中的几大事件》
对于文件级缓存来说，我们要知道两点，一为文件的ＵＲＬ，二为文件的
下面是HttpModuleCache的核心代码
/// <summary>
/// CacheHttpModule类
/// </summary>
internal class CacheHttpModule : IHttpModule
{
public void Dispose()
{
}
private List<string> listNeedCacheExtend;
private string stringClearCache = "zzl";//域名中第一段 url 如果是此字符，则表示此次请求是清除缓存 如： http://www.domain.com/zzl/*******
public void Init(HttpApplication context)
{
context.BeginRequest += new EventHandler(context_BeginRequest);
context.ReleaseRequestState += new EventHandler(context_ReleaseRequestState);
listNeedCacheExtend = new List<string>();
string extends = WebConfig.GetUserSection("CacheInfo", "ExtendTypes", ".html|.htm");
foreach (string s in extends.Split('|'))
{
if (!string.IsNullOrEmpty(s) && !listNeedCacheExtend.Contains(s.Trim()))
listNeedCacheExtend.Add(s.Trim());
}
}
public void context_BeginRequest(object sender, EventArgs e)
{
var application = (HttpApplication)sender;
if (IsNeedCache(application)) //检测当前请求是否需缓存
{
string key = string.Empty; ;
string extend = VirtualPathUtility.GetExtension(application.Context.Request.FilePath).ToLower();
if (IsClearCache(application, out key))
{
if (CacheManage.Container(key, extend))//缓存中存在，则清除缓存，结束请求
{
application.Context.Response.Write(CacheManage.Remove(key, extend));
}
application.CompleteRequest();
}
else
{
#region 使用页面压缩
ResponseCompressionType compressionType = this.GetCompressionMode(application.Context.Request);
if (compressionType != ResponseCompressionType.None)
{
application.Context.Response.AppendHeader("Content-Encoding", compressionType.ToString().ToLower());
if (compressionType == ResponseCompressionType.GZip)
{
application.Context.Response.Filter = new GZipStream(application.Context.Response.Filter, CompressionMode.Compress);
}
else
{
application.Context.Response.Filter = new DeflateStream(application.Context.Response.Filter, CompressionMode.Compress);
}
}
#endregion
if (CacheManage.Container(key, extend))//缓存中存在，则直接返回内容，结束请求
{
CacheManage.Write(application, key);
application.CompleteRequest();
}
}
}
}
/// <summary>
/// 检测当前请求是否需缓存,如果是则将此次结果添加至缓存,如果此次请求出错，不会执行至此
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
public void context_ReleaseRequestState(object sender, EventArgs e)
{
var application = (HttpApplication)sender;
if (application.Context.Response.StatusCode == 200)
{
string strT = null;
string extend = VirtualPathUtility.GetExtension(application.Context.Request.FilePath).ToLower();
if (IsNeedCache(application) && !IsClearCache(application, out strT))
{
string key = application.Context.Request.Url.AbsoluteUri;
//是否需要添加缓存，
if (!CacheManage.Container(key, extend))
{
application.Context.Response.Filter = new ResponseFilter(application.Context.Response.Filter, key, extend, application.Context.Response.ContentEncoding);
}
}
}
}
public void context_EndRequest(object sender, EventArgs e)
{
var application = (HttpApplication)sender;
string key = application.Context.Request.Url.AbsoluteUri;
application.Context.Response.Write("<Br>CacheMdule EndRequest");
}
/// <summary>
/// 检测当前请求类型(url扩展名)确定是否需缓存
/// 如果类型需缓存，但扩展名是html或htm且存在相对应的物理文件的，不执行缓存操作
/// </summary>
/// <param name="strFilePath"></param>
/// <returns></returns>
private bool IsNeedCache(HttpApplication application)
{
bool boolNeedCache = false;
string stringExtend = VirtualPathUtility.GetExtension(application.Context.Request.FilePath).ToLower();
if (null != listNeedCacheExtend) //url扩展名是否满足条件
{
boolNeedCache = listNeedCacheExtend.Contains(stringExtend);
}
if (boolNeedCache)
{
if (stringExtend == ".html" || stringExtend == ".htm")
{
if (System.IO.File.Exists(application.Context.Request.PhysicalPath)) //存在对应物理文件
{
boolNeedCache = false;
}
}
}
return boolNeedCache;
}
/// <summary>
/// 检测当次请求是否是清除缓存的
/// True 清除缓存 False 不是清除缓存的
/// </summary>
/// <param name="application"></param>
/// <param name="url">真实的URL地址</param>
/// <returns></returns>
private bool IsClearCache(HttpApplication application, out string url)
{
bool boolClearCache = false;
url = application.Context.Request.Url.AbsoluteUri;
string domain = application.Context.Request.Url.Host;
Regex regex = new Regex("http://" + domain + "/" + stringClearCache + "/", RegexOptions.Singleline | RegexOptions.Compiled | RegexOptions.IgnoreCase);
if (regex.IsMatch(url))
{
boolClearCache = true;
url = "http://" + domain + "/" + url.Replace(regex.Match(url).Captures[0].Value, string.Empty);
}
return boolClearCache;
}
/// <summary>
/// 获取客户端支持的压缩类型
/// </summary>
/// <param name="request"></param>
/// <returns></returns>
private ResponseCompressionType GetCompressionMode(System.Web.HttpRequest request)
{
string acceptEncoding = request.Headers["Accept-Encoding"];
if (string.IsNullOrEmpty(acceptEncoding))
return ResponseCompressionType.None;
acceptEncoding = acceptEncoding.ToUpperInvariant();
if (acceptEncoding.Contains("GZIP"))
return ResponseCompressionType.GZip;
else if (acceptEncoding.Contains("DEFLATE"))
return ResponseCompressionType.Deflate;
else
return ResponseCompressionType.None;
}
private enum ResponseCompressionType
{
None, GZip, Deflate
}
}
对于上面的HttpModule来说，还需要在config文件中进行相应的配置，代码如下
"true" >
<add name="CacheHttpModule" type="HttpModuleCache.CacheHttpModule,HttpModuleCache"/>
</modules>
程序运行后当检测到合法的文件后（如你之前对html和shtml结尾的文件进行缓存），就会生成文件到服务器的指定位置，下次访问时，直接通过ＵＲＬ生成的服务器本地路径，将静态文件返回到客户端即可，不过，有个地方要注意，由于这种方法生成的缓存文件，它的位置不是固定的，所以，在引用ＣＳＳ，ＪＳ这种文件时，要用绝对路径的形式。
没有用绝对路径时
用了绝对路径后
怎么样，这种文件级缓存的方式大家都掌握了吧！
下载完整HttpModuleCache项目
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作者：仓储大叔，张占岭，
荣誉：微软MVP
