AppBuilder（二）UseStageMarker

 1 public void Init(HttpApplication context)
 2         {
 3             IntegratedPipelineBlueprint blueprint = LazyInitializer.EnsureInitialized(
 4                 ref _blueprint,
 5                 ref _blueprintInitialized,
 6                 ref _blueprintLock,
 7                 InitializeBlueprint);
 8     
 9             if (blueprint != null)
10             {
11                 var integratedPipelineContext = new IntegratedPipelineContext(blueprint);
12                 integratedPipelineContext.Initialize(context);
13             }
14         }

 1 private IntegratedPipelineBlueprint InitializeBlueprint()
 2         {
 3             IntegratedPipelineBlueprintStage firstStage = null;
 4 
 5             Action<IAppBuilder> startup = OwinBuilder.GetAppStartup();    //这就到了前面所讲的流程了，寻找Startup，但在Invoke之前进行了EnableIntegratedPipeline调用
 6             OwinAppContext appContext = OwinBuilder.Build(builder =>
 7             {
 8                 EnableIntegratedPipeline(builder, stage => firstStage = stage);
 9                 startup.Invoke(builder);
10             });
11 
12             string basePath = Utils.NormalizePath(HttpRuntime.AppDomainAppVirtualPath);    //获取虚拟路径
13             return new IntegratedPipelineBlueprint(appContext, firstStage, basePath);    //pipeline已经构建完毕，返回第一个stage
14         }

 1 //EnableIntegratedPipeline的第二个参数是一个Action
 2 private static void EnableIntegratedPipeline(IAppBuilder app, Action<IntegratedPipelineBlueprintStage> onStageCreated)
 3         {
 4             var stage = new IntegratedPipelineBlueprintStage { Name = "PreHandlerExecute" };    //新建一个pipelineStage，只有 Name = "PreHandlerExecute"，其他属性未初始化
 5             onStageCreated(stage);    //实际上就是使firstStage指向刚新建的pipelineStage，如果你足够仔细的话
 6     //你会发现这实际上是定义的pipelineStage的最后一个
 7             Action<IAppBuilder, string> stageMarker = (builder, name) =>
 8             {
 9                 Func<AppFunc, AppFunc> decoupler = next =>
10                 {    //next是一个AppFunc委托，如果当前stage.Name与传入的name相同，则仍然返回next，next实际上就是下一个stage的入口
11                     if (string.Equals(name, stage.Name, StringComparison.OrdinalIgnoreCase))
12                     {
13                         // no decoupling needed when pipeline is already split at this name
14                         return next;
15                     }
16                     if (!IntegratedPipelineContext.VerifyStageOrder(name, stage.Name))    //如果当前的stage.Name的order小于传入的name，仍然返回next
17                     {
18                         // Stage markers added out of order will be ignored.
19                         // Out of order stages/middleware may be run earlier than expected.
20                         // TODO: LOG
21                         return next;
22                     }    //如果当前的stage.Name的order大于传入的name，将当前stage的入口点设置为next，新建一个pipelineStage
23                     stage.EntryPoint = next;
24                     stage = new IntegratedPipelineBlueprintStage
25                     {
26                         Name = name,
27                         NextStage = stage,
28                     };
29                     onStageCreated(stage);    //更新firstStage
30                     return (AppFunc)IntegratedPipelineContext.ExitPointInvoked;    //当前stage已经构建完毕，再用一个AppFunc作为当前middleware的返回值
31                 };
32                 app.Use(decoupler);    //decouper是一个Func<AppFunc,AppFunc>委托，所以会使用前一章所说的第一种app.Use方法，直接将其压入List中
33             };
34             app.Properties[Constants.IntegratedPipelineStageMarker] = stageMarker;    //这里将stageMarker绑定到app.Properties中，这将是本文的重点
35             app.Properties[Constants.BuilderDefaultApp] = (Func<IDictionary<string, object>, Task>)IntegratedPipelineContext.DefaultAppInvoked;
36         }

 1 public static IAppBuilder UseCookieAuthentication(this IAppBuilder app, CookieAuthenticationOptions options, PipelineStage stage)
 2         {
 3             if (app == null)
 4             {
 5                 throw new ArgumentNullException("app");
 6             }
 7 
 8             app.Use(typeof(CookieAuthenticationMiddleware), app, options);
 9             app.UseStageMarker(stage);
10             return app;
11         }

 1 public static IAppBuilder UseStageMarker(this IAppBuilder app, string stageName)
 2         {
 3             if (app == null)
 4             {
 5                 throw new ArgumentNullException("app");
 6             }
 7 
 8             object obj;
 9             if (app.Properties.TryGetValue(IntegratedPipelineStageMarker, out obj))    //寻找app.Propertise中的StageMarker方法，也就是上文OwinHttpModule存进去的方法
10             {
11                 var addMarker = (Action<IAppBuilder, string>)obj;
12                 addMarker(app, stageName);
13             }
14             return app;
15 
16         }

public object Build(Type returnType)
        {
            return BuildInternal(returnType);
        }