Asp.Net生命周期系列四

上回我们说的当一个Http请求来到HttpModule这里的时候，Asp.Net内部并未对这个Http请求做出任何的处理，我们可以对这个Http请求添加一些我们需要的信息，以方便我们控制这个Http请求。我们添加控制信息一般情况下是通过添加一些事件来控制的，那么HttpModule内部到底有哪些事件呢，他们的执行顺序又是怎样的呢？

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

2、验证HttpModule生命周期 
与HttpHandler的交互： 

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，处理完后将对其控制权又还给HttpModule容器——之后Session失效。

在系列一种我们说到，当我们的项目经理（HttpApplication）拿到包含有我们整个请求信息的上下文对象Context（内部包含主要的Request对象和Response对象）之后。它会按照一个由HttpRunTime事先根据webconfig文件建立好的HttpModule列表去工作，其实啊，就是按照这样一个表的顺序去把Http请求流【传递】一遍罢了。

那么现在我有个问题想问一下大家，你们认为这个Http请求究竟会怎么样流过这些HttpModule呢？

我的配置文件是这样写的：（MyHttpModule1已经注释掉了哦，看清楚，写系列三时用到了MyHttpModule1,）

    <httpModules>
      <!--<add name="MyHttpModel"  type="ClassLibrary1.MyHttpModel,ClassLibrary1"/>-->
      <add name="MyHttpModel2" type="ClassLibrary1.MyHttpModule2,ClassLibrary1"/>
      <add name="MyHttpModel3" type="ClassLibrary1.MyHttpModule3,ClassLibrary1"/>
    </httpModules>

我给你们两种选择：

第一种：谁在前面谁是老大啊，那自然是先流过MyHttpModule2，过完之后才能轮到MyHttpModule3啊，这就是所谓的先来先服务吗，谁让人家比你靠前呢。

第二种：凭什么你MyHttpModule2在前面Http请求就要先流过你，然后才能轮到我MyHttpModule3呢，不行，必须先轮流着来，这样才公平吗。

那么究竟是怎么样的呢，我不想解释，直接看代码

下面是两个自定义的HttpModule，代码一模一样，就是换了个名字

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/>");        }    }}

下面是要请求的Default.aspx页面

namespace ClassLibrary1{    public partial class Default : System.Web.UI.Page    {        protected void Page_Load(object sender, EventArgs e)        {            Response.Write("这是Default.aspx页面请求的内容信息。");        }    }}

运行起来，我们请求Default.aspx页面看到下面的结果：

看到结果我想就不用解释了吧，Asp.Net声明周期中选择的是第二种选择。

3、利用HttpModule实现终止此次HttpRequest请求

如果我们在MyHttpModule2中的context_BeginRequest事件中就终止了此次的Http请求，那么接下来的事件还会继续往下执行吗？

还是上面的两个自定义HttpModule（MyHttpModule2和MyHttpModule3），我把MyHttpModule2中的context_BeginRequest事件改写如下：

 private void context_BeginRequest(object sender, EventArgs e)
        {

            HttpApplication application = (HttpApplication)sender;
            application.CompleteRequest();
            application.Context.Response.Write("此次Http请求已经终止<br/>");

        }

运行结果如下：

写到这里，我想现在客户端发出一个Http请求经过HttpModule内部时到底怎样执行，执行哪些事件，以及我们能够利用这些事件做些什么你们应该有一定的了解了，如果你还没有了解，请给我留言，再往下我们该介绍真正的处理中心HttpHandler这个东东了，如果您喜欢我的文章，请继续关注。