ASP.NET MVC请求处理管道生命周期的19个关键环节(7-12)
转自http://www.cnblogs.com/darrenji/p/3795676.html
在上一篇"ASP.NET MVC请求处理管道生命周期的19个关键环节(1-6) "，体验了1-6关键环节，本篇继续。
⑦根据IsapiWorkerRequest对象，HttpRuntime创建HttpContext对象
⑧HttpApplicationFactory创建新的或者从HttpApplication池获取现有的、可用的HttpApplication对象
HttpApplication的工作包括：
● 初始化的时候加载全部的HttpModule
● 接收请求
● 在不同阶段引发不同的事件，使得HttpModule通过订阅事件的方式加入到请求的处理过程中
● 在一个特定阶段获取一个IHttpHandler实例，最终将请求交给具体的IHttpHandler来实现
⑨接下来，就是HttpModules发挥作用的时候
所有的HttpModules都实现了IHttpModule接口：
public interface IHttpModule
{
void Init(HttpApplication app);
void Dispose();
}
可见，HttoModules正是由Init方法，根据传入的HttpApplication类型参数，订阅了HttpApplication的所有事件。
我们自定义一个HttpModule：
public class TestModule : IHttpModule
{
public void Dispose(){}
public void Init(HttpApplication app)
{
app.PostAcquireRequestState += new EventHandler(app_PostAcuiredRequestState);
app.PreRequestHandlerExecute += new EventHandler(app_PreRequestHandlerExecute);
}
void app_PreRequestHandlerExecute(object sender, EventArgs e)
{
//TODO:
}
void app_PostAcquiredRequestState(object sender, EventArgs e)
{
//TODO:
}
}
⑩当某个请求与一个规则匹配后，ASP.NET会调用匹配的HttpHandlerFactory的GetHandler方法来获取一个HttpHandler实例， 最后由一个HttpHandler实例来处理当前请求，生成响应内容
所有的HttpHandlers都实现了IHttpHandler接口：
public interface IHttpHandler
{
bool IsReusable{get;}
void ProcessRequest(HttpContext context);
}
比如我们可以自定义一个HttpHandler来响应一类特定的请求：
public class Login : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
string username = context.Request.Form["name"];
string password = context.Request.Form["password"];
if(password="sth")
{
System.Web.Security.FormsAuthentication.SetAuthCookie(username, false);
context.Response.Write("ok");
}
else
{
context.Response.Write("用户名和密码不正确");
}
}
}
⑾ASP.NET MVC的入口在UrlRoutingModule,即订阅了HttpApplication的第7个管道事件PostResolveRequestCahce,换句话说，是在HtttpApplication的第7个管道事件处对请求进行了拦截
UrlRouteModlue实现了IHttpModule：
public class UrlRoutingModule : IHttpModule
{
// Fields
private static readonly object _contextKey = new object();
private static readonly object _requestDataKey = new object();
private RouteCollection _routeCollection;
// Methods
protected virtual void Dispose()
{
}
protected virtual void Init(HttpApplication application)
{
if (application.Context.Items[_contextKey] == null)
{
application.Context.Items[_contextKey] = _contextKey;
application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);
}
}
private void OnApplicationPostResolveRequestCache(object sender, EventArgs e)
{
HttpContextBase context = new HttpContextWrapper(((HttpApplication) sender).Context);
this.PostResolveRequestCache(context);
}
[Obsolete("This method is obsolete. Override the Init method to use the PostMapRequestHandler event.")]
public virtual void PostMapRequestHandler(HttpContextBase context)
{
}
public virtual void PostResolveRequestCache(HttpContextBase context)
{
RouteData routeData = this.RouteCollection.GetRouteData(context);
if (routeData != null)
{
IRouteHandler routeHandler = routeData.RouteHandler;
if (routeHandler == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
}
if (!(routeHandler is StopRoutingHandler))
{
RequestContext requestContext = new RequestContext(context, routeData);
context.Request.RequestContext = requestContext;
IHttpHandler httpHandler = routeHandler.GetHttpHandler(requestContext);
if (httpHandler == null)
{
throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, SR.GetString("UrlRoutingModule_NoHttpHandler"), new object[] { routeHandler.GetType() }));
}
if (httpHandler is UrlAuthFailureHandler)
{
if (!FormsAuthenticationModule.FormsAuthRequired)
{
throw new HttpException(0x191, SR.GetString("Assess_Denied_Description3"));
}
UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
}
else
{
context.RemapHandler(httpHandler);
}
}
}
}
void IHttpModule.Dispose()
{
this.Dispose();
}
void IHttpModule.Init(HttpApplication application)
{
this.Init(application);
}
// Properties
public RouteCollection RouteCollection
{
get
{
if (this._routeCollection == null)
{
this._routeCollection = RouteTable.Routes;
}
return this._routeCollection;
}
set
{
this._routeCollection = value;
}
}
}
UrlRoutingModule是在Web.config或默认的web.config中配置：
<httpModules>
......
<add name="UrlRoutingModule-4.0" type="System.Web.Routing.UrlRoutingModule" />
</httpModules>
⑿而在请求到达UrlRoutingModule之前，我们在全局文件中做了如下配置
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
......
BundleConfig.RegisterBundles(BundleTable.Bundles);
}
}
public class RouteConfig
{
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
);
}
}
这意味着：在HttpApplication的第一个管道事件BeginRequest处，通过MapRoute()方法把路由注册到了RouteCollection中。在实际使用中，UrlRoutingModule是通过RouteTable的静态属性RouteCollection获取路由。
ASP.NET MVC请求处理管道生命周期的19个关键环节系列包括：
