IIS在接到一個新的http請求後,最終會調用asp.net_isapi.dll的 ISAPI擴展(特指IIS6.0環境,iis7.0的應用程序池默認為集成方式,相對有所變化),然後傳遞到httpRuntime Pipe(http運行時管道),Asp.Net這時才開始運行(即HttpRunTime是Asp.Net真正的入口),HttpRunTime會為每 個asp.net應用自動創建一個HttpApplication的實例,而該實例中又包含以下屬性:
注1
Application -->相當於傳統意義上asp時代的application對象,通常用於定義一個asp.net應用的全局變量
Context -->HttpContext(上下文)類的實例【Asp.Net新增的】
Modules -->影響當前應用程序的HttpModule模塊集合
Request -->類似於asp中的Request對象,通常用於接收一些特定的值(比如Request.Form或Request.QueryString)
Response -->類似於asp中的Response對象,通常用於向做頁面輸出指定內容(比如Resonse.Write)
Server -->類似於asp中的Server對象,通過它能獲得一些服務端的信息(比如Server.MapPath)
Session -->類似於asp中的Session對象
User -->用於獲取用戶認證相關的安全信息
從上面的屬性可以發現:很多其實在asp年代已在使用,只有Context,Modules,User這三個是Asp.Net新增的
HttpApplication類除了具備"注1"的幾個屬性外,還有自己的方法,這裡特別提一下Init方法和Dispose方法,這二個方法均可重載.
它們的調用時機為:
Init方法在Application_Start之後調用,而Dispose在Application_End之前調用,另外 Application_Start在整個asp.net應用的生命周期內只激發一次(比如IIS啟動或網站啟動時),類似的 Application_End也只有當asp.net應用程序關閉時被調用(比如IIS停止或網站停止時)
除了Application_Start和Application_End方法,HttpApplication還提供了以下事件:
這些事件包括前面提到的可重載的Init及Dispose方法,再加上Session對應的Session_Start與Session_End方法,均可直接在Global.ascx.cs中以Application_XXX的形式使用(因為Global.ascx.cs中定義的類Global本身就是繼承自HttpApplication的)
復制代碼 代碼如下:
public class Global : System.Web.HttpApplication
再來看一下相對asp而言,新增的Context,Modules,User這三個屬性
Context:
Context即HttpContext類的實例,在幾乎整個aspx頁面生命周期中,Context上下文一直伴隨著各個環節向下傳遞
所以我們幾乎可以在web應用中的任何環節,用HttpContext.Current來引用到當前的上下文實例,從HttpContext的定義上,還可以發現Context本身的屬性中,又可以得到 Application,ApplicationInstance,Profile,Response.Request...等對象的實例引用
回想一下:
復制代碼 代碼如下:
public class Handler1 : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
context.Response.Write("Hello World");
}
public bool IsReusable
{
get
{
return false;
}
}
}
我們在使用一個ashx文件時,ProcessRequest方法便是把當前上下文傳遞進來,進而通過context得到Response對象的引用,最終可以向頁面輸出任何想要的內容.
Modules:
每一個實現了IHttpModule接口的類,就可以被認為是Http模塊組件,可以理解為http請求攔截器,攔截到http請求後,它能修改正在被處理的Context上下文,完事兒之後,再把控制權交還給管道,如果還有其它模塊,則依次繼續處理,直到所有Modules集合中的 HttpModule都“爽”完為止(注:可憐的http請求就這樣給各個httpModule輪X了)
asp.net2.0默認內置了很多HttpModule,從Machine.Config文件中可以發現以下默認的內置模塊:
注2
AnonymouseIdentification --為匿名用戶分配一個臨時身份
FileAuthorization --驗證用戶是否有請求文件的Windows NT許可
FormsAuthentication --窗體身份驗證模塊(如果沒有這個模塊,asp.net就無法以用戶名/密碼[即FOrms]方式驗證)
OutputCache --輸出緩存模塊
PassportAuthentication --PassPort驗證模塊
Profile --用戶配置模塊(如果沒有它,asp.net中就無法使用Profile)
RoleManager --角色管理
SessionSate --會話狀態模塊
UrlAuthorization --基於URL的身份驗證模塊
WindowsAuthentication --Windows和IIS身份驗證模塊
User:
如果您使用過asp.net2.0內置的Membership/Role機制來進行訪問認證,就會對User對象感到很熟悉,比如:
復制代碼 代碼如下:
if (HttpContext.Current.User.Identity.IsAuthenticated)
{
//用戶登錄過了...
}
我們常用它來判斷當前浏覽用戶的登錄狀態,關於User類的更詳細定義,可參見MSDN
生命周期:
最後再來回顧一下Asp.Net中Page頁的生命周期,Page中定義了幾個事件:
總體上講:一個ASPX頁面被請求時,最終的生命周期就是由Page中定義的上述事件(還有一些可重載的回調方法)以及以前提到的HttpApplication類中定義的事件(以相應的回調方法)共同觸發或調用,最終疊加形成的一連串處理過程。
如果先不考慮HttpApplication中的事件處理方法(即不考慮我們在Global.ascx.cs中定義的Application_XXX處理方法),Page中的事件(方法)常規觸發(調用)順序為:
01.Page_PreInit
02.Page_Init
03.Page_InitComplete
04.Page_PreLoad
05.Page_Load
06.Page_LoadComplete
07.Page_PreRender
08.Page_SaveStateComplete
09.Page_Unload
這是在Page頁面未回發,且不考慮頁面子控件的前提下正常的順序,如果加入頁面回發(比如在頁面中放一個asp:Button,然後在Button的Click回發事件中加入處理函數)後,順序稍微有些變化:
01.Page_PreInit
02.Page_Init
03.Page_InitComplete
04.Page_PreLoad
05.Page_Load
06.Button1_Click
07.Page_LoadComplete
08.Page_PreRender
09.Page_SaveStateComplete
10.Page_Unload
不同的地方在於:回發事件Button1_Click在Page_Load後被觸發.
最後再把HttpApplication的事件考慮進來,看下疊加後的順序,不過先別著急,我們先來看一種特殊情況,如果一個asp.net應用根目錄下未設置默認頁,這時直接浏覽根目錄,比如http://localhost:2345/ 時,Globl.ascx.cs中定義的Application_XXX方法的調用順序如下:
2010-03-28 15:01:39 413 Application_Start
2010-03-28 15:01:39 491 Init
2010-03-28 15:01:39 491 Application_BeginRequest
2010-03-28 15:01:39 506 Application_AuthenticateRequest
2010-03-28 15:01:39 506 Application_PostAuthenticateRequest
2010-03-28 15:01:39 506 Application_AuthorizeRequest
2010-03-28 15:01:39 522 Application_PostAuthorizeRequest
2010-03-28 15:01:39 522 Application_ResolveRequestCache
2010-03-28 15:01:39 522 Application_PostResolveRequestCache
2010-03-28 15:01:39 522 Application_PostMapRequestHandler
2010-03-28 15:01:39 522 Application_AcquireRequestState
2010-03-28 15:01:39 537 Application_PostAcquireRequestState
2010-03-28 15:01:39 537 Application_PreRequestHandlerExecute
2010-03-28 15:01:39 553 Application_Error
2010-03-28 15:01:39 553 Application_EndRequest
2010-03-28 15:01:39 569 Application_PreSendRequestHeaders
2010-03-28 15:01:39 569 Application_PreSendRequestContent
可以看到會觸發Application_Error事件,即HttpRuntime認為這是一個錯誤.
緊接著再浏覽一個實際存在的頁面,如果這時應用程序有嚴重錯誤,導致Application關閉(比如web.config配置錯誤),調用的順序如下:
2010-03-28 15:03:47 704 Application_BeginRequest
2010-03-28 15:03:47 704 Application_AuthenticateRequest
2010-03-28 15:03:47 766 Application_PostAuthenticateRequest
2010-03-28 15:03:47 766 Application_AuthorizeRequest
2010-03-28 15:03:47 766 Application_PostAuthorizeRequest
2010-03-28 15:03:47 766 Application_ResolveRequestCache
2010-03-28 15:03:47 783 Application_PostResolveRequestCache
2010-03-28 15:03:48 667 Application_PostMapRequestHandler
2010-03-28 15:03:48 667 Application_AcquireRequestState
2010-03-28 15:03:48 683 Application_PostAcquireRequestState
2010-03-28 15:03:48 698 Application_PreRequestHandlerExecute
2010-03-28 15:03:48 745 Page_PreInit
2010-03-28 15:04:02 903 Page_Unload
2010-03-28 15:04:02 903 Application_Error
2010-03-28 15:04:02 918 Application_EndRequest
2010-03-28 15:04:02 996 Application_PreSendRequestHeaders
2010-03-28 15:04:02 996 Application_PreSendRequestContent
2010-03-28 15:04:03 371 Application_Disposed
2010-03-28 15:04:03 371 Dispose
2010-03-28 15:04:03 386 Application_End
對比剛才的順序,會發現Application_Start及Init沒有再次被調用,也印證了文章前面提到的一些結論 (Application_Start在整個asp.net應用生命周期內只觸發一次),而且從最後的三個輸出能知道:應用程序關閉時 Application_Disposed,Dispose,Application_End按順序調用.
再"重新"浏覽(指web Server重啟)一下正常訪問的頁面,在不出錯也不回發的情況下,順序如下:
2010-03-28 15:08:11 513 Application_Start
2010-03-28 15:08:11 591 Init
2010-03-28 15:08:11 591 Application_BeginRequest
2010-03-28 15:08:11 591 Application_AuthenticateRequest
2010-03-28 15:08:11 591 Application_PostAuthenticateRequest
2010-03-28 15:08:11 606 Application_AuthorizeRequest
2010-03-28 15:08:11 606 Application_PostAuthorizeRequest
2010-03-28 15:08:11 606 Application_ResolveRequestCache
2010-03-28 15:08:11 606 Application_PostResolveRequestCache
2010-03-28 15:08:11 622 Application_PostMapRequestHandler
2010-03-28 15:08:11 637 Application_EndRequest
2010-03-28 15:08:11 637 Application_PreSendRequestHeaders
2010-03-28 15:08:11 637 Application_PreSendRequestContent
2010-03-28 15:08:11 637 Application_BeginRequest
2010-03-28 15:08:11 637 Application_AuthenticateRequest
2010-03-28 15:08:11 653 Application_PostAuthenticateRequest
2010-03-28 15:08:11 653 Application_AuthorizeRequest
2010-03-28 15:08:11 653 Application_PostAuthorizeRequest
2010-03-28 15:08:11 653 Application_ResolveRequestCache
2010-03-28 15:08:11 653 Application_PostResolveRequestCache
2010-03-28 15:08:11 653 Application_PostMapRequestHandler
2010-03-28 15:08:11 653 Session_Start
2010-03-28 15:08:11 653 Application_AcquireRequestState
2010-03-28 15:08:11 653 Application_PostAcquireRequestState
2010-03-28 15:08:11 653 Application_PreRequestHandlerExecute
2010-03-28 15:08:11 669 Page_PreInit
2010-03-28 15:08:11 684 Page_Init
2010-03-28 15:08:11 684 Page_InitComplete
2010-03-28 15:08:11 684 Page_PreLoad
2010-03-28 15:08:11 684 Page_Load
2010-03-28 15:08:11 684 Page_LoadComplete
2010-03-28 15:08:11 684 Page_PreRender
2010-03-28 15:08:11 684 Page_SaveStateComplete
2010-03-28 15:08:11 700 Page_Unload
2010-03-28 15:08:11 700 Application_PostRequestHandlerExecute
2010-03-28 15:08:11 700 Application_ReleaseRequestState
2010-03-28 15:08:11 700 Application_PostReleaseRequestState
2010-03-28 15:08:11 700 Application_UpdateRequestCache
2010-03-28 15:08:11 700 Application_PostUpdateRequestCache
2010-03-28 15:08:11 700 Application_EndRequest
2010-03-28 15:08:11 700 Application_PreSendRequestHeaders
2010-03-28 15:08:11 700 Application_PreSendRequestContent
2010-03-28 15:08:11 793 Application_BeginRequest
2010-03-28 15:08:11 793 Application_AuthenticateRequest
2010-03-28 15:08:11 793 Application_PostAuthenticateRequest
2010-03-28 15:08:11 793 Application_AuthorizeRequest
2010-03-28 15:08:11 793 Application_PostAuthorizeRequest
2010-03-28 15:08:11 793 Application_ResolveRequestCache
2010-03-28 15:08:11 793 Application_PostResolveRequestCache
2010-03-28 15:08:11 809 Application_PostMapRequestHandler
2010-03-28 15:08:11 809 Application_AcquireRequestState
2010-03-28 15:08:11 809 Application_PostAcquireRequestState
2010-03-28 15:08:11 809 Application_PreRequestHandlerExecute
2010-03-28 15:08:11 825 Application_PostRequestHandlerExecute
2010-03-28 15:08:11 825 Application_ReleaseRequestState
2010-03-28 15:08:11 840 Application_PostReleaseRequestState
2010-03-28 15:08:11 949 Application_UpdateRequestCache
2010-03-28 15:08:11 949 Application_PostUpdateRequestCache
2010-03-28 15:08:11 965 Application_EndRequest
2010-03-28 15:08:11 981 Application_PreSendRequestHeaders
2010-03-28 15:08:11 981 Application_PreSendRequestContent
哇!原來一個頁面訪問下來,會調用到這麼多的方法,怪不得很多高並發的大型網站,通常都要自己寫一個精減的HttpHandler用來取代Page做為基類,以期望獲得更好的性能
最後:我們在做網站開發時,不可能只用到Page頁,很多時候還會用到UserControl(用戶自定義控件),先看下它的繼承關系,比如我們創建了一個TestUserControl的用戶控件
TestUserControl --> UserControl ---> TemplateControl --> Control
最終在Control類的定義下,可以看到
這似乎表明用戶控件中,應該有Page_Init,Page_Load,Page_Unload...等事件,通常我們只用到Init,Load事件,如果加入一個用戶控件後,整個生命周期就更復雜了:
2010-06-12 15:35:28 042 Application_Start
2010-06-12 15:35:28 072 Init
2010-06-12 15:35:28 072 Application_BeginRequest
2010-06-12 15:35:28 082 Application_AuthenticateRequest
2010-06-12 15:35:28 082 Application_PostAuthenticateRequest
2010-06-12 15:35:28 092 Application_AuthorizeRequest
2010-06-12 15:35:28 102 Application_PostAuthorizeRequest
2010-06-12 15:35:28 102 Application_ResolveRequestCache
2010-06-12 15:35:28 112 Application_PostResolveRequestCache
2010-06-12 15:35:28 122 Application_PostMapRequestHandler
2010-06-12 15:35:28 142 Application_EndRequest
2010-06-12 15:35:28 142 Application_PreSendRequestHeaders
2010-06-12 15:35:28 142 Application_PreSendRequestContent
2010-06-12 15:35:28 152 Application_BeginRequest
2010-06-12 15:35:28 152 Application_AuthenticateRequest
2010-06-12 15:35:28 162 Application_PostAuthenticateRequest
2010-06-12 15:35:28 162 Application_AuthorizeRequest
2010-06-12 15:35:28 162 Application_PostAuthorizeRequest
2010-06-12 15:35:28 172 Application_ResolveRequestCache
2010-06-12 15:35:28 172 Application_PostResolveRequestCache
2010-06-12 15:35:28 172 Application_PostMapRequestHandler
2010-06-12 15:35:28 172 Session_Start
2010-06-12 15:35:28 172 Application_AcquireRequestState
2010-06-12 15:35:28 182 Application_PostAcquireRequestState
2010-06-12 15:35:28 182 Application_PreRequestHandlerExecute
2010-06-12 15:35:28 192 Page_PreInit
2010-06-12 15:35:28 192 TestUserControl.Page_Init
2010-06-12 15:35:28 202 Page_Init
2010-06-12 15:35:28 202 TestUserControl.TestProperty.Set
2010-06-12 15:35:28 202 Page_InitComplete
2010-06-12 15:35:28 202 Page_PreLoad
2010-06-12 15:35:28 202 Page_Load
2010-06-12 15:35:28 202 TestUserControl.Page_Load
2010-06-12 15:35:28 202 TestUserControl.ShowData()
2010-06-12 15:35:28 212 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 212 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 212 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 212 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 212 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 222 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 222 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 222 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 222 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 222 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 232 TestUserControl.Repeater1.ItemDataBound()
2010-06-12 15:35:28 232 Page_LoadComplete
2010-06-12 15:35:28 232 Page_PreRender
2010-06-12 15:35:28 232 TestUserControl.Page_PreRender
2010-06-12 15:35:28 242 Page_SaveStateComplete
2010-06-12 15:35:28 242 TestUserControl.Page_Unload
2010-06-12 15:35:28 252 Page_Unload
2010-06-12 15:35:28 252 Application_PostRequestHandlerExecute
2010-06-12 15:35:28 252 Application_ReleaseRequestState
2010-06-12 15:35:28 252 Application_PostReleaseRequestState
2010-06-12 15:35:28 262 Application_UpdateRequestCache
2010-06-12 15:35:28 262 Application_PostUpdateRequestCache
2010-06-12 15:35:28 262 Application_EndRequest
2010-06-12 15:35:28 272 Application_PreSendRequestHeaders
2010-06-12 15:35:28 272 Application_PreSendRequestContent
2010-06-12 15:35:28 282 Application_BeginRequest
2010-06-12 15:35:28 292 Application_AuthenticateRequest
2010-06-12 15:35:28 292 Application_PostAuthenticateRequest
2010-06-12 15:35:28 302 Application_AuthorizeRequest
2010-06-12 15:35:28 302 Application_PostAuthorizeRequest
2010-06-12 15:35:28 302 Application_ResolveRequestCache
2010-06-12 15:35:28 312 Application_PostResolveRequestCache
2010-06-12 15:35:28 312 Application_PostMapRequestHandler
2010-06-12 15:35:28 322 Application_AcquireRequestState
2010-06-12 15:35:28 322 Application_PostAcquireRequestState
2010-06-12 15:35:28 322 Application_PreRequestHandlerExecute
2010-06-12 15:35:28 332 Application_PostRequestHandlerExecute
2010-06-12 15:35:28 332 Application_ReleaseRequestState
2010-06-12 15:35:28 332 Application_PostReleaseRequestState
2010-06-12 15:35:28 342 Application_UpdateRequestCache
2010-06-12 15:35:28 342 Application_PostUpdateRequestCache
2010-06-12 15:35:28 342 Application_EndRequest
2010-06-12 15:35:28 342 Application_PreSendRequestHeaders
2010-06-12 15:35:28 342 Application_PreSendRequestContent
2010-06-12 15:36:40 034 Session_End