缓存篇(Cache)~第三回 HttpModule实现网页的文件级缓存

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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

　 <modules runAllManagedModulesForAllRequests="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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