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。
本系列：
