ASP.NET 请求处理 二(MVC流程)

//MVC 处理流程
public class UrlRoutingModule : IHttpModule{
    //mvc框架注册了一个IHttpModule  在里面注册了PostResolveRequestCache事件来处理请求路由
    protected virtual void Init(HttpApplication application)
    {
        if (application.Context.Items[UrlRoutingModule._contextKey] != null)
        {
            return;
        }
        application.Context.Items[UrlRoutingModule._contextKey] = UrlRoutingModule._contextKey;
        application.PostResolveRequestCache += new EventHandler(this.OnApplicationPostResolveRequestCache);
    }
    private void OnApplicationPostResolveRequestCache(object sender, EventArgs e)
    {
        HttpContextBase context = new HttpContextWrapper(((HttpApplication)sender).Context);
        this.PostResolveRequestCache(context);
    }
    
    public virtual void PostResolveRequestCache(HttpContextBase context)
    {
        //从控制器路由表里面找到合适的页面路由
        RouteData routeData = this.RouteCollection.GetRouteData(context);
        if (routeData == null)
        {
            return;
        }
        //从RouteData里找到RouteHandler  MVC默认是MvcRouteHandler来处理的
        IRouteHandler routeHandler = routeData.RouteHandler;
        if (routeHandler == null)
        {
            throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, SR.GetString("UrlRoutingModule_NoRouteHandler"), new object[0]));
        }
        if (routeHandler is StopRoutingHandler)
        {
            return;
        }
        RequestContext requestContext = new RequestContext(context, routeData);
        context.Request.RequestContext = requestContext;
        //调用MvcRouteHandler.GetHttpHandler  获取 MvcHandler 对象
        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))
        {
            //将Handler保存为remapHandler  MvcHandler 接管http处理流程
            context.RemapHandler(httpHandler);
            return;
        }
        if (FormsAuthenticationModule.FormsAuthRequired)
        {
            UrlAuthorizationModule.ReportUrlAuthorizationFailure(HttpContext.Current, this);
            return;
        }
        throw new HttpException(401, SR.GetString("Assess_Denied_Description3"));
    }
}

//RouteCollectionRoute.GetRouteData 遍历路由列表
public override RouteData GetRouteData(HttpContextBase httpContext)
{
    List<RouteData> list = new List<RouteData>();
    foreach (RouteBase current in this._subRoutes)
    {
        RouteData routeData = current.GetRouteData(httpContext);
        if (routeData != null)
        {
            list.Add(routeData);
        }
    }
    return RouteCollectionRoute.CreateDirectRouteMatch(this, list);
}
//Route.GetRouteData 分析路由数据是否满足url的解析条件
public override RouteData GetRouteData(HttpContextBase httpContext)
{
    string virtualPath = httpContext.Request.AppRelativeCurrentExecutionFilePath.Substring(2) + httpContext.Request.PathInfo;
    RouteValueDictionary routeValueDictionary = this._parsedRoute.Match(virtualPath, this.Defaults);
    if (routeValueDictionary == null)
    {
        return null;
    }
    RouteData routeData = new RouteData(this, this.RouteHandler);
    if (!this.ProcessConstraints(httpContext, routeValueDictionary, RouteDirection.IncomingRequest))
    {
        return null;
    }
    foreach (KeyValuePair<string, object> current in routeValueDictionary)
    {
        routeData.Values.Add(current.Key, current.Value);
    }
    if (this.DataTokens != null)
    {
        foreach (KeyValuePair<string, object> current2 in this.DataTokens)
        {
            routeData.DataTokens[current2.Key] = current2.Value;
        }
    }
    return routeData;
}

//MvcHandler.ProcessRequest
protected internal virtual void ProcessRequest(HttpContextBase httpContext)
{
    IController controller;
    IControllerFactory controllerFactory;
    //从controllerFactory中取出或新建Controller
    this.ProcessRequestInit(httpContext, out controller, out controllerFactory);
    try
    {
        //执行controller 
        controller.Execute(this.RequestContext);
    }
    finally
    {
        //释放controller
        controllerFactory.ReleaseController(controller);
    }
}