HttpModule对HttpApplication实例进行处理,而HttpApplication有很多事件(对应不同的生命期),这样就衍生出HttpModule内部事件机制和生命周期。
(1)、HttpModule的事件
       
BeginRequest     指示请求处理开始
AuthenticateRequest     封装请求身份验证过程
AuthorizeRequest     封装检查是否能利用以前缓存的输出页面处理请求的过程
ResolveRequestCache     从缓存中得到相应时候触发
AcquireRequestState     加载初始化Session时候触发
PreRequestHandlerExecute     在Http请求进入HttpHandler之前触发
PostRequestHandlerExecute     在Http请求进入HttpHandler之后触发
ReleaseRequestState     存储Session状态时候触发
UpdateRequestCache     更新缓存信息时触发
EndRequest     在Http请求处理完成的时候触发
PreSendRequestHenaders     在向客户端发送Header之前触发
PreSendRequestConternt     在向客户端发送内容之前触发

 

说明:
a、BenginRequest和EndRequest分别是HttpModule容器最开始的和最后的事件;
b、EndRequest之后还会触发PreSendRequestHeaders事件和PreSendRequestContent事件,这不是在HttpModule外的两个事件,表示HttpModule结束,即将开始向Client发送数据。

(2)、验证HttpModule生命周期
与HttpHandler的交互:
HttpModuleHandler

说明:
a、HttpModule容器会将HttpRequest传递到HttpHandler容器,这个时间点是ResolveRequestCache事件
b、HttpModule容器会建立HttpHandler实例作为入口——Session从此生效
c、触发AcquireRequestState事件以及PreRequestHandlerExecute事件
d、HttpModule容器便将对HttpRequest的控制权转让给HttpHandler容器
e、HttpHandler容器处理HttpRequest——使用自身的ProcessRequest方法,将对其控制权又还给HttpModule容器——之后Session失效。

验证生命周期代码:

using System;

using System.Collections.Generic;

using System.Text;

using System.Web;

namespace MyHttpModule

{

    public class ValidaterHttpModuleEvents : IHttpModule

    {

        public void Dispose()

        { }

        /// <summary>

        /// 验证HttpModule事件机制

        /// </summary>

        /// <param name="application"></param>

        public void Init(HttpApplication application)

        {

            application.BeginRequest += new EventHandler(application_BeginRequest);

            application.EndRequest += new EventHandler(application_EndRequest);

            application.AcquireRequestState += new EventHandler(application_AcquireRequestState);

            application.AuthenticateRequest += new EventHandler(application_AuthenticateRequest);

            application.AuthorizeRequest += new EventHandler(application_AuthorizeRequest);

            application.PreRequestHandlerExecute += new EventHandler(application_PreRequestHandlerExecute);

            application.PostRequestHandlerExecute += new EventHandler(application_PostRequestHandlerExecute);

            application.ReleaseRequestState += new EventHandler(application_ReleaseRequestState);

            application.ResolveRequestCache += new EventHandler(application_ResolveRequestCache);

            application.PreSendRequestHeaders += new EventHandler(application_PreSendRequestHeaders);

            application.PreSendRequestContent += new EventHandler(application_PreSendRequestContent);

        }

        private void application_BeginRequest(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_BeginRequest<br/>");

        }

        private void application_EndRequest(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_EndRequest<br/>");

        }

        private void application_PreRequestHandlerExecute(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_PreRequestHandlerExecute<br/>");

        }

        private void application_PostRequestHandlerExecute(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_PostRequestHandlerExecute<br/>");

        }

        private void application_ReleaseRequestState(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_ReleaseRequestState<br/>");

        }

        private void application_AcquireRequestState(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_AcquireRequestState<br/>");

        }

        private void application_PreSendRequestContent(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_PreSendRequestContent<br/>");

        }

        private void application_PreSendRequestHeaders(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_PreSendRequestHeaders<br/>");

        }

        private void application_ResolveRequestCache(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_ResolveRequestCache<br/>");

        }

        private void application_AuthorizeRequest(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_AuthorizeRequest<br/>");

        }

        private void application_AuthenticateRequest(object sender, EventArgs e)

        {

            HttpApplication application = (HttpApplication)sender;

            application.Context.Response.Write("application_AuthenticateRequest<br/>");

        }

    }

}

<add name="HttpModule1" type="MyHttpModule.HttpModule1,MyHttpModule"/>

<add name="HttpModule2" type="MyHttpModule.HttpModule2,MyHttpModule"/>

HttpModule1和HttpModule2模仿ValidaterHttpModuleEvents编写(除了类名改变外,事件和方法不变),不贴代码了。运行结果如下:

HttpModuleCompare

从运行结果可以看到,在web.config文件中引入自定义HttpModule的顺序就决定了多个自定义HttpModule在处理一个HTTP请求的接管顺序。

(3)、利用HttpModule实现终止此次HttpRequest请求

在BeginRequest事件中,使用HttpApplication.CompleteRequest()方法可以实现当满足一定条件时终止此次HttpRequest请求

using System;

using System.Web;

namespace ClassLibrary1

{

    public class MyHttpModule : IHttpModule

    {

        public void Dispose() { }

        public void Init(HttpApplication context)

        {

            context.BeginRequest += new EventHandler(Application_BeginRequest);

        }

        public void Application_BeginRequest(object sender, EventArgs e)

        {

            HttpApplication application = sender as HttpApplication;

            application.CompleteRequest();

            application.Context.Response.Write("请求被终止");

        }

    }

}

说明:
a、对于一个HttpModule,在BeginRquest中终止,但是仍然会调用EndRequest事件,以及 PreSendRequestHeaders事件和PreSendRequestContent事件。也可以说是直接跳转到EndRequest事件,而 不会调用这期间的事件
b、如果有两个HttpModule,在第一个HttpModule的BeginRequest中终止,仅仅不会调用第二 个HttpModule的BeginRequest,但仍然会调用两个EndRequest事件,以及PreSendRequestHeaders事件和 PreSendRequestContent事件。

HttpModule HTTP请求 最后修改于 2011-10-02 21:41:55
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