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。