MVC源碼分析 - Controller創建和創建擴展

上一篇, 出現了一個至關重要的類:MvcHandler, 接下來就來看一下MvcHandler吧. 先不看具體方法, 先看一下類裡面的情況.

//這裡實現了兩個重要的介面, 非同步處理和同步處理的介面
public class MvcHandler : IHttpAsyncHandler, IHttpHandler, IRequiresSessionState
{
    // Fields
    private ControllerBuilder _controllerBuilder;
    private static readonly object _processRequestTag;
    internal static readonly string MvcVersion;
    public static readonly string MvcVersionHeaderName;

    // Methods
    static MvcHandler();
    public MvcHandler(RequestContext requestContext);
    protected internal virtual void AddVersionHeader(HttpContextBase httpContext);
    protected virtual IAsyncResult BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, object state);
    protected internal virtual IAsyncResult BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, object state);
    protected internal virtual void EndProcessRequest(IAsyncResult asyncResult);
    private static string GetMvcVersionString();
    protected virtual void ProcessRequest(HttpContext httpContext);
    protected internal virtual void ProcessRequest(HttpContextBase httpContext);
    private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory);
    private void RemoveOptionalRoutingParameters();
    IAsyncResult IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData);
    void IHttpAsyncHandler.EndProcessRequest(IAsyncResult result);
    void IHttpHandler.ProcessRequest(HttpContext httpContext);

    // Properties
    internal ControllerBuilder ControllerBuilder { get; set; }
    public static bool DisableMvcResponseHeader { get; set; }
    protected virtual bool IsReusable { get; }
    public RequestContext RequestContext { get; private set; }
    bool IHttpHandler.IsReusable { get; }
}

從上面看, 有兩種執行方式, 一種是同步的, 一種是非同步的. 那預設情況下, 其實會走非同步的方式. 但是這裡呢, 我想用同步的方式去分析, 其實過程原理都是一樣的, 只是方式不同.

一、解析

註意到這個類, 實現了三個介面, 那第三個介面是幹啥的呢? 先看一下這個介面的內容.

public interface IRequiresSessionState
{
}

點進去, 發現這個介面沒有任何方法, 那麼他是乾什麼的呢? 

其實他是一種標誌, 或者叫標記, 表示這個類有對Session的訪問許可權, 包括讀寫. 如果你想自定義Http處理程式, 又想操作Session的話, 記得實現這個介面.

接下來, 回歸正題了.  來看一下這裡的 PR 方法.

protected virtual void ProcessRequest(HttpContext httpContext)
{
    HttpContextBase base2 = new HttpContextWrapper(httpContext);
    this.ProcessRequest(base2);
}

protected internal virtual void ProcessRequest(HttpContextBase httpContext)
{
    IController controller;
    IControllerFactory factory;
    this.ProcessRequestInit(httpContext, out controller, out factory);
    try
    {
        controller.Execute(this.RequestContext);
    }
    finally
    {
        factory.ReleaseController(controller);
    }
}

這裡也就只有三個方法了, 我們一個一個分析.

1. ProcessRequestInit()

//MvcHandler
private void ProcessRequestInit(HttpContextBase httpContext, out IController controller, out IControllerFactory factory)
{
    HttpContext current = HttpContext.Current;
    if ((current != null) && (ValidationUtility.IsValidationEnabled(current) == true))
    {
        ValidationUtility.EnableDynamicValidation(current);
    }
    this.AddVersionHeader(httpContext);
    this.RemoveOptionalRoutingParameters();
　　 //從路由中獲取控制器的名稱
    string requiredString = this.RequestContext.RouteData.GetRequiredString("controller");
　　 //獲取控制器工廠
    factory = this.ControllerBuilder.GetControllerFactory();
　　 //利用控制器工廠創建控制器類
    controller = factory.CreateController(this.RequestContext, requiredString);
    if (controller == null)
    {
        throw new InvalidOperationException(string.Format(CultureInfo.CurrentCulture, 
　　　　　　MvcResources.ControllerBuilder_FactoryReturnedNull, new object[] { factory.GetType(), requiredString }));
    }
}

1.1 從路由中獲取控制器名稱 - GetRequiredString

public string GetRequiredString(string valueName)
{
    object obj2;
    if (this.Values.TryGetValue(valueName, out obj2))
    {
        string str = obj2 as string;
        if (!string.IsNullOrEmpty(str))
        {
            return str;
        }
    }
    throw new InvalidOperationException(string.Format(CultureInfo.CurrentUICulture, 
　　　　SR.GetString("RouteData_RequiredValue"), new object[] { valueName }));
}

1.2 獲取創建工廠 - GetControllerFactory

public IControllerFactory GetControllerFactory()
{
    return this._serviceResolver.Current;
}

1.3 創建控制器類 - CreateController

//DefaultControllerFactory類
public virtual IController CreateController(RequestContext requestContext, string controllerName)
{
    if (requestContext == null)
    {
        throw new ArgumentNullException("requestContext");
    }
    if (string.IsNullOrEmpty(controllerName))
    {
        throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");
    }
    Type controllerType = this.GetControllerType(requestContext, controllerName);
    return this.GetControllerInstance(requestContext, controllerType);
}

1.3.1 GetControllerType()

protected internal virtual Type GetControllerType(RequestContext requestContext, string controllerName)
{
    object obj2;
    Type type;
    if (string.IsNullOrEmpty(controllerName))
    {
        throw new ArgumentException(MvcResources.Common_NullOrEmpty, "controllerName");
    }
    if ((requestContext != null) && requestContext.RouteData.DataTokens.TryGetValue("Namespaces", out obj2))
    {
        IEnumerable<string> source = obj2 as IEnumerable<string>;
        if ((source != null) && source.Any<string>())
        {
            HashSet<string> namespaces = new HashSet<string>(source, StringComparer.OrdinalIgnoreCase);
            type = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, namespaces);
            if (type == null)
            {
                bool flag = false;
                if (!flag.Equals(requestContext.RouteData.DataTokens["UseNamespaceFallback"]))
                {
                    goto Label_0092;
                }
            }
            return type;
        }
    }
Label_0092:
    if (this.ControllerBuilder.DefaultNamespaces.Count > 0)
    {
        HashSet<string> set2 = new HashSet<string>(this.ControllerBuilder.DefaultNamespaces, 
　　　　　　StringComparer.OrdinalIgnoreCase);
        type = this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, set2);
        if (type != null)
        {
            return type;
        }
    }
    return this.GetControllerTypeWithinNamespaces(requestContext.RouteData.Route, controllerName, null);
}

這裡會從路由中, 獲取控制器所在的命名空間. 不管由這個限制還是沒有這個限制, 都是能正常創建控制器的. 先看這裡.

private Type GetControllerTypeWithinNamespaces(RouteBase route, string controllerName, HashSet<string> namespaces)
{
　　 //MVC-ControllerTypeCache.xml文件中獲取Controller的緩存
    this.ControllerTypeCache.EnsureInitialized(this.BuildManager);
　　 //從之前獲取的緩存中, 來獲取控制器的類型
    ICollection<Type> controllerTypes = this.ControllerTypeCache.GetControllerTypes(controllerName, namespaces);
    switch (controllerTypes.Count)
    {
        case 0:
            return null;

        case 1:
            return controllerTypes.First<Type>();
    }
    throw CreateAmbiguousControllerException(route, controllerName, controllerTypes);
}

 1.3.2 GetControllerInstance()

protected internal virtual IController GetControllerInstance(RequestContext requestContext, Type controllerType)
{
    if (controllerType == null)
    {
        throw new HttpException(0x194, 
　　　　　　string.Format(CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_NoControllerFound, 　　
　　　　　　new object[] { requestContext.HttpContext.Request.Path }));
    }
    if (!typeof(IController).IsAssignableFrom(controllerType))
    {
        throw new ArgumentException(　　
　　　　　　string.Format(CultureInfo.CurrentCulture, 
　　　　　　MvcResources.DefaultControllerFactory_TypeDoesNotSubclassControllerBase, 
　　　　　　new object[] { controllerType }), "controllerType");
    }
    return this.ControllerActivator.Create(requestContext, controllerType);
}

來看一下這裡的Create方法, 看一下具體是怎麼創建的.

public IController Create(RequestContext requestContext, Type controllerType)
{
    IController controller;
    try
    {
        controller = (IController) (this._resolverThunk().GetService(controllerType) ?? 
　　　　　　Activator.CreateInstance(controllerType));
    }
    catch (Exception exception)
    {
        throw new InvalidOperationException(
　　　　　　string.Format(CultureInfo.CurrentCulture, MvcResources.DefaultControllerFactory_ErrorCreatingController, 
　　　　　　new object[] { controllerType }), exception);
    }
    return controller;
}

這裡有一個擴展點, 像之前篇幅提到的Autofac Mvc部分, 在這裡, 反饋的GetService(controllerType)就不是一個空值了.

如果沒有搜索到這些擴展, 就會預設反射的方式來創建控制器.

Demo: 值的註意的是, 這些擴展都是要實現 IDependencyResolve 介面的, 此例子是從Autofac.Integration.Mvc.dll中來的

public class AutofacDependencyResolver : IDependencyResolver
{
    // Fields
    private readonly Action<ContainerBuilder> _configurationAction;
    private readonly ILifetimeScope _container;
    private ILifetimeScopeProvider _lifetimeScopeProvider;

    // Methods
    public AutofacDependencyResolver(ILifetimeScope container);
    public AutofacDependencyResolver(ILifetimeScope container, ILifetimeScopeProvider lifetimeScopeProvider);
    public AutofacDependencyResolver(ILifetimeScope container, Action<ContainerBuilder> configurationAction);
    public AutofacDependencyResolver(ILifetimeScope container, 
　　　　ILifetimeScopeProvider lifetimeScopeProvider, 
　　　　Action<ContainerBuilder> configurationAction);
    public object GetService(Type serviceType);
    public IEnumerable<object> GetServices(Type serviceType);

    // Properties
    public ILifetimeScope ApplicationContainer { get; }
    public static AutofacDependencyResolver Current { get; }
    public ILifetimeScope RequestLifetimeScope { get; }
}

2. Execute()

這裡執行的是ControllerBase的Execute方法. 是一個虛方法. 這裡的方法, 留到下一篇分析了.

protected virtual void Execute(RequestContext requestContext)
{
    if (requestContext == null)
    {
        throw new ArgumentNullException("requestContext");
    }
    if (requestContext.HttpContext == null)
    {
        throw new ArgumentException(MvcResources.ControllerBase_CannotExecuteWithNullHttpContext, "requestContext");
    }
    this.VerifyExecuteCalledOnce();
    this.Initialize(requestContext);
    using (ScopeStorage.CreateTransientScope())
    {
        this.ExecuteCore();
    }
}

3. ReleaseController()

這個方法, 顧名思義, 是釋放資源的. 來看一下, DefaultControllerFactory 類中的此方法

public virtual void ReleaseController(IController controller)
{
    IDisposable disposable = controller as IDisposable;
    if (disposable != null)
    {
        disposable.Dispose();
    }
}

 從上面的分析, 基本可以看到控制器的創建過程, 至於他的執行過程, 就放到下一篇去了, 內容還是很多的.

二、擴展

從上面的分析能看到這裡有一個依賴註入擴展, 那麼下麵, 就這個依賴註入擴展, 來舉一個小例子.(殘破的例子, 別介意, 能演示功能的)

用的Autofac, 不過與上面不同, 並沒有引用上面的程式集, 只引用Autofac.dll一個程式集就可以了.

我先從之前Autofac篇章, 弄了一個Helper類過來, 精簡一下.

public class IocContainer
{
    private static ContainerBuilder builder;

    private static IContainer container;

    static IocContainer()
    {
        builder = new ContainerBuilder();
    }

    public static void RegisterTypes(params Type[] types)
    {
        builder.RegisterTypes(types);
    }

    public static void Build()
    {
        container = builder.Build();
    }

    public static object Create(Type t)
    {
        return container.Resolve(t);
    }
}

然後, 我建了一個Resolver.

public class MyDependencyResolver : IDependencyResolver
{
    public object GetService(Type serviceType)
    {
        bool flag = true;
        string path = @"F:\MVC解析\MyControllerFac\1.txt";
        if (!File.Exists(path))
        {
            File.Create(path).Close();
        }

        try
        {
            return IocContainer.Create(serviceType);
        }
        catch (Exception)
        {
            flag = false;
            //這裡需要註意, 需要返回一個null值, 否則會報錯
            return null;
        }
        finally
        {
            using (FileStream fs = new FileStream(path, FileMode.Append))
            {
                var msg = flag ? "命中" : "飄過";
                byte[] bt = System.Text.Encoding.UTF8.GetBytes(serviceType.ToString() + " : " + msg + "\r\n");
                fs.Write(bt, 0, bt.Length);
　　　　　　　 　　 fs.Close();
            }
        }
    }

    public IEnumerable<object> GetServices(Type serviceType)
    {
        var res = new List<object>();
        try
        {
            var obj = IocContainer.Create(serviceType);
            res.Add(obj);
        }
        catch (Exception)
        {

        }
        return res;
    }
}

現在前置工作做好了, 可以去MVC中, 註冊我自己的方法了.

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();

    WebApiConfig.Register(GlobalConfiguration.Configuration);
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
　　 
　　 //這裡我就省懶了, 並沒有寫到單獨的方法中取
    IocContainer.RegisterTypes(System.Reflection.Assembly.Load("MyMvc").GetTypes());

    IocContainer.Build();

    DependencyResolver.SetResolver(new MyDependencyResolver());
}

OK, 萬事俱備, 只差測試. 跑起來吧

頁面能正常訪問, 那麼是不是走的我哪裡呢? 從頁面上肯定看不出來, 所以我加了點東西, 看一下1.txt

 從這裡來看, 並不是只有 HomeController 走了我自定義的那個方式, 這也是為什麼一定要返回一個null了. 對於這些飄過的, 就只能使用MVC預設的方式了. 還是很神奇的.

目錄已同步