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.NET Core开发日志——Controller

  • lzyq2322
  • 2019-03-12
  • 286人已阅读
简介在理清路由的工作流程后,接下来需要考虑的,是MVC框架如何生成Controller以及它的生成时机。根据以前ASP.NETMVC的经验,Controller应该是由一个Control

在理清路由的工作流程后,接下来需要考虑的,是MVC框架如何生成Controller以及它的生成时机。

根据以前ASP.NET MVC的经验,Controller应该是由一个ControllerFactory构建的。查看ASP.NET Core MVC的源码,果然是有一个DefaultControllerFactory类,并且不出意外的,它拥有一个CreateController方法。

public virtual object CreateController(ControllerContext context){ ... var controller = _controllerActivator.Create(context); foreach (var propertyActivator in _propertyActivators) { propertyActivator.Activate(context, controller); } return controller;}

但细推其使用的场合,只出现在ControllerFactoryProvider的构造方法内部,且仅是用于判断所传入的controllerFactory类型是否是DefaultControllerFactory。

public ControllerFactoryProvider( IControllerActivatorProvider activatorProvider, IControllerFactory controllerFactory, IEnumerable<IControllerPropertyActivator> propertyActivators){ ... _activatorProvider = activatorProvider; // Compat: Delegate to the IControllerFactory if it"s not the default implementation. if (controllerFactory.GetType() != typeof(DefaultControllerFactory)) { _factoryCreateController = controllerFactory.CreateController; _factoryReleaseController = controllerFactory.ReleaseController; } _propertyActivators = propertyActivators.ToArray();}

再看ControllerFactoryProvider内部的CreateControllerFactory方法。这更像是一个真正创建Controller的工厂方法。

public Func<ControllerContext, object> CreateControllerFactory(ControllerActionDescriptor descriptor){ ... if (_factoryCreateController != null) { return _factoryCreateController; } var controllerActivator = _activatorProvider.CreateActivator(descriptor); var propertyActivators = GetPropertiesToActivate(descriptor); object CreateController(ControllerContext controllerContext) { var controller = controllerActivator(controllerContext); for (var i = 0; i < propertyActivators.Length; i++) { var propertyActivator = propertyActivators[i]; propertyActivator(controllerContext, controller); } return controller; } return CreateController;}

创建方式分为两种,一种是使用自定义的工厂方法,另一种是通过ControllerActivatorProvider的CreateActivator方法。

public Func<ControllerContext, object> CreateActivator(ControllerActionDescriptor descriptor){ ... var controllerType = descriptor.ControllerTypeInfo?.AsType(); ... if (_controllerActivatorCreate != null) { return _controllerActivatorCreate; } var typeActivator = ActivatorUtilities.CreateFactory(controllerType, Type.EmptyTypes); return controllerContext => typeActivator(controllerContext.HttpContext.RequestServices, arguments: null);}

明白了如何创建Controller,下面开始调查创建Controller的时机。

ControllerFactoryProvider类的CreateControllerFactory方法是被ControllerActionInvokerCache类的GetCachedResult方法调用。

public (ControllerActionInvokerCacheEntry cacheEntry, IFilterMetadata[] filters) GetCachedResult(ControllerContext controllerContext){ var cache = CurrentCache; var actionDescriptor = controllerContext.ActionDescriptor; IFilterMetadata[] filters; if (!cache.Entries.TryGetValue(actionDescriptor, out var cacheEntry)) { var filterFactoryResult = FilterFactory.GetAllFilters(_filterProviders, controllerContext); filters = filterFactoryResult.Filters; var parameterDefaultValues = ParameterDefaultValues .GetParameterDefaultValues(actionDescriptor.MethodInfo); var objectMethodExecutor = ObjectMethodExecutor.Create( actionDescriptor.MethodInfo, actionDescriptor.ControllerTypeInfo, parameterDefaultValues); var controllerFactory = _controllerFactoryProvider.CreateControllerFactory(actionDescriptor); var controllerReleaser = _controllerFactoryProvider.CreateControllerReleaser(actionDescriptor); var propertyBinderFactory = ControllerBinderDelegateProvider.CreateBinderDelegate( _parameterBinder, _modelBinderFactory, _modelMetadataProvider, actionDescriptor); var actionMethodExecutor = ActionMethodExecutor.GetExecutor(objectMethodExecutor); cacheEntry = new ControllerActionInvokerCacheEntry( filterFactoryResult.CacheableFilters, controllerFactory, controllerReleaser, propertyBinderFactory, objectMethodExecutor, actionMethodExecutor); cacheEntry = cache.Entries.GetOrAdd(actionDescriptor, cacheEntry); } else { // Filter instances from statically defined filter descriptors + from filter providers filters = FilterFactory.CreateUncachedFilters(_filterProviders, controllerContext, cacheEntry.CachedFilters); } return (cacheEntry, filters);}

其值作为ControllerActionInvokerCacheEntry对象的一部分被方法返回。

GetCachedResult方法的上层调用者是ControllerActionInvokerProvider类的OnProvidersExecuting方法。

public void OnProvidersExecuting(ActionInvokerProviderContext context){ ... if (context.ActionContext.ActionDescriptor is ControllerActionDescriptor) { var controllerContext = new ControllerContext(context.ActionContext); // PERF: These are rarely going to be changed, so let"s go copy-on-write. controllerContext.ValueProviderFactories = new CopyOnWriteList<IValueProviderFactory>(_valueProviderFactories); controllerContext.ModelState.MaxAllowedErrors = _maxModelValidationErrors; var cacheResult = _controllerActionInvokerCache.GetCachedResult(controllerContext); var invoker = new ControllerActionInvoker( _logger, _diagnosticSource, controllerContext, cacheResult.cacheEntry, cacheResult.filters); context.Result = invoker; }}

ControllerActionInvokerCacheEntry对象又被作为ControllerActionInvoker对象的一部分为ActionInvokerProviderContext的Result属性赋值。

再往上跟踪,到了ActionInvokerFactory类的CreateInvoker方法。

public IActionInvoker CreateInvoker(ActionContext actionContext){ var context = new ActionInvokerProviderContext(actionContext); foreach (var provider in _actionInvokerProviders) { provider.OnProvidersExecuting(context); } for (var i = _actionInvokerProviders.Length - 1; i >= 0; i--) { _actionInvokerProviders[i].OnProvidersExecuted(context); } return context.Result;}

而它的调用者便是MvcRouteHandler或者MvcAttributeRouteHandler。

public Task RouteAsync(RouteContext context){ ... context.Handler = (c) => { var routeData = c.GetRouteData(); var actionContext = new ActionContext(context.HttpContext, routeData, actionDescriptor); if (_actionContextAccessor != null) { _actionContextAccessor.ActionContext = actionContext; } var invoker = _actionInvokerFactory.CreateInvoker(actionContext); if (invoker == null) { throw new InvalidOperationException( Resources.FormatActionInvokerFactory_CouldNotCreateInvoker( actionDescriptor.DisplayName)); } return invoker.InvokeAsync(); }; ...}

到了这里创建Controller的工厂方法还没有被实际调用,此时Controller还是不存在的。所以还需要完成执行ControllerActionInvoker的InvokeAsync方法,或者更准确地说是其基类ResourceInvoker的InvokeAsync方法。

public virtual async Task InvokeAsync(){ try { ... using (_logger.ActionScope(_actionContext.ActionDescriptor)) { ... try { await InvokeFilterPipelineAsync(); } ... } } ...}

从InvokeFilterPipelineAsync方法开始,一系列的处理流程将依据不同状态逐步展开。

private async Task InvokeFilterPipelineAsync(){ var next = State.InvokeBegin; var scope = Scope.Invoker; var state = (object)null; var isCompleted = false; while (!isCompleted) { await Next(ref next, ref scope, ref state, ref isCompleted); }}

而到了State.ActionBegin这一步(ControllerActionInvoker类的Next方法),终于能找到Controller工厂方法被执行的场合。

private Task Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted){ switch (next) { case State.ActionBegin: { var controllerContext = _controllerContext; _cursor.Reset(); _instance = _cacheEntry.ControllerFactory(controllerContext); _arguments = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase); var task = BindArgumentsAsync(); if (task.Status != TaskStatus.RanToCompletion) { next = State.ActionNext; return task; } goto case State.ActionNext; } ... } }}

最后以一张流程图总结上面的探寻过程。

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