上回我們說的當一個Http請求來到HttpModule這里的時候，Asp.Net內部並未對這個Http請求做出任何的處理，我們可以對這個Http請求添加一些我們需要的信息，以方便我們控制這個Http請求。我們添加控制信息一般情況下是通過添加一些事件來控制的，那么HttpModule內部到底有哪些事件呢，他們的執行順序又是怎樣的呢？
1、HttpModule的事件
| BeginRequest | 指示請求處理開始 |
| AuthenticateRequest | 封裝請求身份驗證過程 |
| AuthorizeRequest | 封裝檢查是否能利用以前緩存的輸出頁面處理請求的過程 |
| ResolveRequestCache | 從緩存中得到相應時候觸發 |
| AcquireRequestState | 加載初始化Session時候觸發 |
| PreRequestHandlerExecute | 在Http請求進入HttpHandler之前觸發 |
| PostRequestHandlerExecute | 在Http請求進入HttpHandler之后觸發 |
| ReleaseRequestState | 存儲Session狀態時候觸發 |
| UpdateRequestCache | 更新緩存信息時觸發 |
| EndRequest | 在Http請求處理完成的時候觸發 |
| PreSendRequestHenaders | 在向客戶端發送Header之前觸發 |
| PreSendRequestConternt | 在向客戶端發送內容之前觸發 |
2、驗證HttpModule生命周期
與HttpHandler的交互： 
說明：
a、HttpModule容器會將HttpRequest傳遞到HttpHandler容器，這個時間點是ResolveRequestCache事件
b、HttpModule容器會建立HttpHandler實例作為入口——Session從此生效
c、觸發AcquireRequestState事件以及PreRequestHandlerExecute事件
d、HttpModule容器便將對HttpRequest的控制權轉讓給HttpHandler容器
e、HttpHandler容器處理HttpRequest——使用自身的ProcessRequest方法，處理完后將對其控制權又還給HttpModule容器——之后Session失效。
在系列一種我們說到，當我們的項目經理（HttpApplication）拿到包含有我們整個請求信息的上下文對象Context（內部包含主要的Request對象和Response對象）之后。它會按照一個由HttpRunTime事先根據webconfig文件建立好的HttpModule列表去工作，其實啊，就是按照這樣一個表的順序去把Http請求流【傳遞】一遍罷了。
那么現在我有個問題想問一下大家，你們認為這個Http請求究竟會怎么樣流過這些HttpModule呢？
我的配置文件是這樣寫的：（MyHttpModule1已經注釋掉了哦，看清楚，寫系列三時用到了MyHttpModule1,）
<httpModules>
<!--<add name="MyHttpModel" type="ClassLibrary1.MyHttpModel,ClassLibrary1"/>-->
<add name="MyHttpModel2" type="ClassLibrary1.MyHttpModule2,ClassLibrary1"/>
<add name="MyHttpModel3" type="ClassLibrary1.MyHttpModule3,ClassLibrary1"/>
</httpModules>
我給你們兩種選擇：
第一種：誰在前面誰是老大啊，那自然是先流過MyHttpModule2，過完之后才能輪到MyHttpModule3啊，這就是所謂的先來先服務嗎，誰讓人家比你靠前呢。
第二種：憑什么你MyHttpModule2在前面Http請求就要先流過你，然后才能輪到我MyHttpModule3呢，不行，必須先輪流着來，這樣才公平嗎。
那么究竟是怎么樣的呢，我不想解釋，直接看代碼
下面是兩個自定義的HttpModule，代碼一模一樣，就是換了個名字
namespace ClassLibrary1 { public class MyHttpModule2:IHttpModule { public void Dispose() { throw new NotImplementedException(); } public void Init(HttpApplication context) { context.BeginRequest+=new EventHandler(context_BeginRequest); context.AuthenticateRequest+=new EventHandler(context_AuthenticateRequest); context.AuthorizeRequest+=new EventHandler(context_AuthorizeRequest); context.ResolveRequestCache+=new EventHandler(context_ResolveRequestCache); context.AcquireRequestState+=new EventHandler(context_AcquireRequestState); context.PreRequestHandlerExecute+=new EventHandler(context_PreRequestHandlerExecute); context.PostRequestHandlerExecute+=new EventHandler(context_PostRequestHandlerExecute); context.ReleaseRequestState+=new EventHandler(context_ReleaseRequestState); context.UpdateRequestCache+=new EventHandler(context_UpdateRequestCache); context.EndRequest+=new EventHandler(context_EndRequest); context.PreSendRequestHeaders+=new EventHandler(context_PreSendRequestHeaders); context.PreSendRequestContent+=new EventHandler(context_PreSendRequestContent); } private void context_BeginRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_BeginRequest<br/>"); } private void context_AuthenticateRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_AuthenticateRequest<br/>"); } private void context_AuthorizeRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_AuthorizeRequest<br/>"); } private void context_ResolveRequestCache(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_ResolveRequestCache<br/>"); } private void context_AcquireRequestState(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_AcquireRequestState<br/>"); } private void context_PreRequestHandlerExecute(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_PreRequestHandlerExecute<br/>"); } private void context_PostRequestHandlerExecute(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_PostRequestHandlerExecute<br/>"); } private void context_UpdateRequestCache(object sender, EventArgs e) { HttpApplication application = sender as HttpApplication; application.Context.Response.Write("MyHttpModule2中的context_UpdateRequestCache<br/>"); } private void context_EndRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_EndRequest<br/>"); } private void context_ReleaseRequestState(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_ReleaseRequestState<br/>"); } private void context_PreSendRequestHeaders(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_PreSendRequestHeaders<br/>"); } private void context_PreSendRequestContent(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule2中的application_PreSendRequestContent<br/>"); }
namespace ClassLibrary1 { public class MyHttpModule3:IHttpModule { public void Dispose() { throw new NotImplementedException(); } public void Init(HttpApplication context) { context.BeginRequest += new EventHandler(context_BeginRequest); context.AuthenticateRequest += new EventHandler(context_AuthenticateRequest); context.AuthorizeRequest += new EventHandler(context_AuthorizeRequest); context.ResolveRequestCache += new EventHandler(context_ResolveRequestCache); context.AcquireRequestState += new EventHandler(context_AcquireRequestState); context.PreRequestHandlerExecute += new EventHandler(context_PreRequestHandlerExecute); context.PostRequestHandlerExecute += new EventHandler(context_PostRequestHandlerExecute); context.ReleaseRequestState += new EventHandler(context_ReleaseRequestState); context.UpdateRequestCache += new EventHandler(context_UpdateRequestCache); context.EndRequest += new EventHandler(context_EndRequest); context.PreSendRequestHeaders += new EventHandler(context_PreSendRequestHeaders); context.PreSendRequestContent += new EventHandler(context_PreSendRequestContent); } private void context_BeginRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_BeginRequest<br/>"); } private void context_AuthenticateRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_AuthenticateRequest<br/>"); } private void context_AuthorizeRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_AuthorizeRequest<br/>"); } private void context_ResolveRequestCache(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_ResolveRequestCache<br/>"); } private void context_AcquireRequestState(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_AcquireRequestState<br/>"); } private void context_PreRequestHandlerExecute(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_PreRequestHandlerExecute<br/>"); } private void context_PostRequestHandlerExecute(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_PostRequestHandlerExecute<br/>"); } private void context_UpdateRequestCache(object sender, EventArgs e) { HttpApplication application = sender as HttpApplication; application.Context.Response.Write("MyHttpModule3中的context_UpdateRequestCache<br/>"); } private void context_EndRequest(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_EndRequest<br/>"); } private void context_ReleaseRequestState(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_ReleaseRequestState<br/>"); } private void context_PreSendRequestHeaders(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_PreSendRequestHeaders<br/>"); } private void context_PreSendRequestContent(object sender, EventArgs e) { HttpApplication application = (HttpApplication)sender; application.Context.Response.Write("MyHttpModule3中的application_PreSendRequestContent<br/>"); } } }
下面是要請求的Default.aspx頁面
namespace ClassLibrary1 { public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Response.Write("這是Default.aspx頁面請求的內容信息。"); } } }
運行起來，我們請求Default.aspx頁面看到下面的結果：
看到結果我想就不用解釋了吧，Asp.Net聲明周期中選擇的是第二種選擇。
3、利用HttpModule實現終止此次HttpRequest請求
如果我們在MyHttpModule2中的context_BeginRequest事件中就終止了此次的Http請求，那么接下來的事件還會繼續往下執行嗎？
還是上面的兩個自定義HttpModule（MyHttpModule2和MyHttpModule3），我把MyHttpModule2中的context_BeginRequest事件改寫如下：
private void context_BeginRequest(object sender, EventArgs e)
{
HttpApplication application = (HttpApplication)sender;
application.CompleteRequest();
application.Context.Response.Write("此次Http請求已經終止<br/>");
}
運行結果如下：
寫到這里，我想現在客戶端發出一個Http請求經過HttpModule內部時到底怎樣執行，執行哪些事件，以及我們能夠利用這些事件做些什么你們應該有一定的了解了，如果你還沒有了解，請給我留言，再往下我們該介紹真正的處理中心HttpHandler這個東東了，如果您喜歡我的文章，請繼續關注。
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