Asp.net的应用程序对象和页面生存周期
IIS在接到一个新的http请求后,最终会调用asp.net_isapi.dll的 ISAPI扩展(特指IIS6.0环境,iis7.0的应用程序池默认为集成方式,相对有所变化),然后传递到httpRuntime Pipe(http运行时管道),Asp.Net这时才开始运行(即HttpRunTime是Asp.Net真正的入口),HttpRunTime会为每 个asp.net应用自动创建一个HttpApplication的实例,而该实例中又包含以下属性:
注1
Application -->相当于传统意义上asp时代的application对象,通常用于定义一个asp.net应用的全局变量
Context -->HttpContext(上下文)类的实例【Asp.Net新增的】
Modules -->影响当前应用程序的HttpModule模块集合
Request -->类似于asp中的Request对象,通常用于接收一些特定的值(比如Request.Form或Request.QueryString)
Response -->类似于asp中的Response对象,通常用于向做页面输出指定内容(比如Resonse.Write)
Server -->类似于asp中的Server对象,通过它能获得一些服务端的信息(比如Server.MapPath)
Session -->类似于asp中的Session对象
User -->用于获取用户认证相关的安全信息
从上面的属性可以发现:很多其实在asp年代已在使用,只有Context,Modules,User这三个是Asp.Net新增的
HttpApplication类除了具备"注1"的几个属性外,还有自己的方法,这里特别提一下Init方法和Dispose方法,这二个方法均可重载.
它们的调用时机为:
Init方法在Application_Start之后调用,而Dispose在Application_End之前调用,另外 Application_Start在整个asp.net应用的生命周期内只激发一次(比如IIS启动或网站启动时),类似的 Application_End也只有当asp.net应用程序关闭时被调用(比如IIS停止或网站停止时)
除了Application_Start和Application_End方法,HttpApplication还提供了以下事件:
这些事件包括前面提到的可重载的Init及Dispose方法,再加上Session对应的Session_Start与Session_End方法,均可直接在Global.ascx.cs中以Application_XXX的形式使用(因为Global.ascx.cs中定义的类Global本身就是继承自HttpApplication的)
public class Global : System.Web.HttpApplication
再来看一下相对asp而言,新增的Context,Modules,User这三个属性
Context:
Context即HttpContext类的实例,在几乎整个aspx页面生命周期中,Context上下文一直伴随着各个环节向下传递
所以我们几乎可以在web应用中的任何环节,用HttpContext.Current来引用到当前的上下文实例,从HttpContext的定义上,还可以发现Context本身的属性中,又可以得到 Application,ApplicationInstance,Profile,Response.Request...等对象的实例引用
回想一下:
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;
}
}
}
我们在使用一个ashx文件时,ProcessRequest方法便是把当前上下文传递进来,进而通过context得到Response对象的引用,最终可以向页面输出任何想要的内容.
Modules:
每一个实现了IHttpModule接口的类,就可以被认为是Http模块组件,可以理解为http请求拦截器,拦截到http请求后,它能修改正在被处理的Context上下文,完事儿之后,再把控制权交还给管道,如果还有其它模块,则依次继续处理,直到所有Modules集合中的 HttpModule都“爽”完为止(注:可怜的http请求就这样给各个httpModule轮X了)
asp.net2.0默认内置了很多HttpModule,从Machine.Config文件中可以发现以下默认的内置模块:
注2
AnonymouseIdentification --为匿名用户分配一个临时身份
FileAuthorization --验证用户是否有请求文件的Windows NT许可
FormsAuthentication --窗体身份验证模块(如果没有这个模块,asp.net就无法以用户名/密码[即FOrms]方式验证)
OutputCache --输出缓存模块
PassportAuthentication --PassPort验证模块
Profile --用户配置模块(如果没有它,asp.net中就无法使用Profile)
RoleManager --角色管理
SessionSate --会话状态模块
UrlAuthorization --基于URL的身份验证模块
WindowsAuthentication --Windows和IIS身份验证模块
User:
如果您使用过asp.net2.0内置的Membership/Role机制来进行访问认证,就会对User对象感到很熟悉,比如:
if (HttpContext.Current.User.Identity.IsAuthenticated)
{
//用户登录过了...
}
我们常用它来判断当前浏览用户的登录状态,关于User类的更详细定义,可参见MSDN
生命周期:
最后再来回顾一下Asp.Net中Page页的生命周期,Page中定义了几个事件:
总体上讲:一个ASPX页面被请求时,最终的生命周期就是由Page中定义的上述事件(还有一些可重载的回调方法)以及以前提到的HttpApplication类中定义的事件(以相应的回调方法)共同触发或调用,最终叠加形成的一连串处理过程。
如果先不考虑HttpApplication中的事件处理方法(即不考虑我们在Global.ascx.cs中定义的Application_XXX处理方法),Page中的事件(方法)常规触发(调用)顺序为:
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
这是在Page页面未回发,且不考虑页面子控件的前提下正常的顺序,如果加入页面回发(比如在页面中放一个asp:Button,然后在Button的Click回发事件中加入处理函数)后,顺序稍微有些变化:
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
不同的地方在于:回发事件Button1_Click在Page_Load后被触发.
最后再把HttpApplication的事件考虑进来,看下叠加后的顺序,不过先别着急,我们先来看一种特殊情况,如果一个asp.net应用根目录下未设置默认页,这时直接浏览根目录,比如http://localhost:2345/ 时,Globl.ascx.cs中定义的Application_XXX方法的调用顺序如下:
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
可以看到会触发Application_Error事件,即HttpRuntime认为这是一个错误.
紧接着再浏览一个实际存在的页面,如果这时应用程序有严重错误,导致Application关闭(比如web.config配置错误),调用的顺序如下:
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
对比刚才的顺序,会发现Application_Start及Init没有再次被调用,也印证了文章前面提到的一些结论 (Application_Start在整个asp.net应用生命周期内只触发一次),而且从最后的三个输出能知道:应用程序关闭时 Application_Disposed,Dispose,Application_End按顺序调用.
再"重新"浏览(指web Server重启)一下正常访问的页面,在不出错也不回发的情况下,顺序如下:
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!原来一个页面访问下来,会调用到这么多的方法,怪不得很多高并发的大型网站,通常都要自己写一个精减的HttpHandler用来取代Page做为基类,以期望获得更好的性能
最后:我们在做网站开发时,不可能只用到Page页,很多时候还会用到UserControl(用户自定义控件),先看下它的继承关系,比如我们创建了一个TestUserControl的用户控件
TestUserControl --> UserControl ---> TemplateControl --> Control
最终在Control类的定义下,可以看到
这似乎表明用户控件中,应该有Page_Init,Page_Load,Page_Unload...等事件,通常我们只用到Init,Load事件,如果加入一个用户控件后,整个生命周期就更复杂了:
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