ASP.NET WebAPI 08 Message,HttpConfiguration,DependencyResolver

Message

WebAPI作为通信架构必定包含包含请求与响应两个方法上的报文，在WebAPI它们分别是HttpRequestMessage,HttpResponseMessage。对于HttpResponseMessage之前在WebAPI返回结果中有应用。

HttpRequestMessage

请求报文包含请求地址(RequestUri),请求方法(Method),头信息(Headers),报文信息(Content)以及Http版本(Versions)

public class HttpRequestMessage : IDisposable

{

public HttpRequestMessage();

public HttpRequestMessage(HttpMethod method, string requestUri);

public HttpRequestMessage(HttpMethod method, Uri requestUri);

public HttpContent Content { get; set; }

public HttpRequestHeaders Headers { get; }

public HttpMethod Method { get; set; }

public IDictionary<string, object> Properties { get; }

public Uri RequestUri { get; set; }

public Version Version { get; set; }

public void Dispose();

protected virtual void Dispose(bool disposing);

public override string ToString();

}

另外，WebAPI提供了一个类型为IDictionary<string,object>的属性Properties。我们可以将做任意对象作为附加属性添加到HttpRequestMessage.

HttpResponseMessage

请求报文包含状态码(StatusCode),原因短句(ReasonPhrase),头信息(Headers),报文信息(Content)以及Http版本(Versions)

public class HttpRequestMessage : IDisposable

{

public HttpRequestMessage();

public HttpRequestMessage(HttpMethod method, string requestUri);

public HttpRequestMessage(HttpMethod method, Uri requestUri);

public HttpContent Content { get; set; }

public HttpRequestHeaders Headers { get; }

public HttpMethod Method { get; set; }

public IDictionary<string, object> Properties { get; }

public Uri RequestUri { get; set; }

public Version Version { get; set; }

public void Dispose();

protected virtual void Dispose(bool disposing);

public override string ToString();

}

HttpConfiguration

HttpConfiguration在WebAPI大概有如下几个作用：

设置通信管道
存储全局信息(比如Filter,Route,Formatter)
提供一个Ioc架构，用于WebAPI的扩展

public class HttpConfiguration : IDisposable

{

public HttpConfiguration();

public HttpConfiguration(HttpRouteCollection routes);

public IDependencyResolver DependencyResolver { get; set; }

public HttpFilterCollection Filters { get; }

public MediaTypeFormatterCollection Formatters { get; }

public IncludeErrorDetailPolicy IncludeErrorDetailPolicy { get; set; }

public Action<HttpConfiguration> Initializer { get; set; }

public Collection<System.Net.Http.DelegatingHandler> MessageHandlers { get; }

public ParameterBindingRulesCollection ParameterBindingRules { get; internal set; }

public ConcurrentDictionary<object, object> Properties { get; }

public HttpRouteCollection Routes { get; }

public ServicesContainer Services { get; internal set; }

public string VirtualPathRoot { get; }

public void Dispose();

protected virtual void Dispose(bool disposing);

public void EnsureInitialized();

}

对于第1 点我们在每6篇已经用到。第2点后面会陆续讲到，本篇只重点讲下第3点。这一功能主要是通过ServicesContainer来完成，即HttpConfiguration中的Services属性。

WebAPI对ServicesContainer的提供的派生类是DefaultServices,在DefaultServices，包含了两种依赖注入方法:1，单一派生类型注入(multi)，2，多派生类型注入(single)，即在注入派生类型的数量有区别。比如在获取url参数的时候有QueryString,RouteData两种方式，而这两种方式是通过QueryStringValueProvider与RouteDataValueProvider两种类型来实现的(实际在DefaultServices注入是这人两个类对应的Factory类)，这两种类型属于平行关系，所以这个时候能需要采用multi方法注入。

这些类型都是在DefaultServces的构造中注入的。

public class DefaultServices : ServicesContainer

{

protected DefaultServices();

public DefaultServices(HttpConfiguration configuration);

protected override void ClearSingle(Type serviceType);

public override object GetService(Type serviceType);

protected override List<object> GetServiceInstances(Type serviceType);

public override IEnumerable<object> GetServices(Type serviceType);

public override bool IsSingleService(Type serviceType);

protected override void ReplaceSingle(Type serviceType, object service);

protected override void ResetCache(Type serviceType);

}

public abstract class ServicesContainer : IDisposable

{

protected ServicesContainer();

public void Add(Type serviceType, object service);

public void AddRange(Type serviceType, IEnumerable<object> services);

public virtual void Clear(Type serviceType);

public virtual void Dispose();

public int FindIndex(Type serviceType, Predicate<object> match);

public abstract object GetService(Type serviceType);

public abstract IEnumerable<object> GetServices(Type serviceType);

public void Insert(Type serviceType, int index, object service);

viceType, int index, IEnumerable<object> services);

public abstract bool IsSingleService(Type serviceType);

public bool Remove(Type serviceType, object service);

public int RemoveAll(Type serviceType, Predicate<object> match);

public void RemoveAt(Type serviceType, int index);

public void Replace(Type serviceType, object service);

public void ReplaceRange(Type serviceType, IEnumerable<object> services);

}

ServicesContainer只提供的了替换与获取的公共方法。因为ServicesContainer只提供了WebAPI中的标准组件，并不想作为一个公共的Ioc容器，而这些标准的组件是WebAPI进行扩展的基础。

下面我写的四个Action分别是获取所有multiServices,获取所有singleServices,向multiServices中添加一个自定义的ValueProviderFactory，向singleServices中添加自定义的IExceptionHandler.

public Dictionary<Type, List<Type>> GetAllMultiServices()

{

Dictionary<Type, List<Type>> result = new Dictionary<Type, List<Type>>();

FieldInfo field = RequestContext.Configuration.Services.GetType().GetField("_defaultServicesMulti",

BindingFlags.NonPublic|BindingFlags.Instance);

Dictionary<Type, List<object>> multiServices = (Dictionary<Type, List<object>>)field.GetValue(RequestContext.Configuration.Services);

foreach (var s in multiServices)

{

List<Type> items = new List<Type>();

foreach (var item in s.Value) {

items.Add(item.GetType());

}

result[s.Key] = items;

}

return result;

}

public Dictionary<Type, Type> GetAllSingleServices()

{

Dictionary<Type, Type> result = new Dictionary<Type, Type>();

FieldInfo field = RequestContext.Configuration.Services.GetType().GetField("_defaultServicesSingle",

BindingFlags.NonPublic | BindingFlags.Instance);

Dictionary<Type, object> services = (Dictionary<Type, object>)field.GetValue(RequestContext.Configuration.Services);

foreach (var s in services)

{

result.Add(s.Key, s.Value==null?null:s.Value.GetType());

}

return result;

}

public Dictionary<Type, List<Type>> AddMultiService()

{

List<ValueProviderFactory> valueProviderFactories=new List<ValueProviderFactory>(){

new QueryStringValueProviderFactory(),

new RouteDataValueProviderFactory(),

new MyValueProviderFactory()

};

RequestContext.Configuration.Services.ReplaceRange(typeof(ValueProviderFactory), valueProviderFactories);

return GetAllMultiServices();

}

public Dictionary<Type, Type> ReplaceSingleService()

{

RequestContext.Configuration.Services.Replace(typeof(IExceptionHandler), new MyExceptionHandler());

return GetAllSingleServices();

}

因为ServicesContainer中的类型注入都是固定的，所以WebAPI给ServicesContainer扩展了一组获取Service的方法

public static class ServicesExtensions

{

public static IHttpActionInvoker GetActionInvoker(this ServicesContainer services);

public static IHttpActionSelector GetActionSelector(this ServicesContainer services);

public static IActionValueBinder GetActionValueBinder(this ServicesContainer services);

public static IApiExplorer GetApiExplorer(this ServicesContainer services);

public static IAssembliesResolver GetAssembliesResolver(this ServicesContainer services);

public static IBodyModelValidator GetBodyModelValidator(this ServicesContainer services);

public static IContentNegotiator GetContentNegotiator(this ServicesContainer services);

public static IDocumentationProvider GetDocumentationProvider(this ServicesContainer services);

public static IExceptionHandler GetExceptionHandler(this ServicesContainer services);

public static IEnumerable<IExceptionLogger> GetExceptionLoggers(this ServicesContainer services);

public static IEnumerable<System.Web.Http.Filters.IFilterProvider> GetFilterProviders(this ServicesContainer services);

public static IHostBufferPolicySelector GetHostBufferPolicySelector(this ServicesContainer services);

public static IHttpControllerActivator GetHttpControllerActivator(this ServicesContainer services);

public static IHttpControllerSelector GetHttpControllerSelector(this ServicesContainer services);

public static IHttpControllerTypeResolver GetHttpControllerTypeResolver(this ServicesContainer services);

public static IEnumerable<System.Web.Http.ModelBinding.ModelBinderProvider> GetModelBinderProviders(this ServicesContainer services);

public static ModelMetadataProvider GetModelMetadataProvider(this ServicesContainer services);

public static IEnumerable<ModelValidatorProvider> GetModelValidatorProviders(this ServicesContainer services);

public static ITraceManager GetTraceManager(this ServicesContainer services);

public static ITraceWriter GetTraceWriter(this ServicesContainer services);

public static IEnumerable<System.Web.Http.ValueProviders.ValueProviderFactory> GetValueProviderFactories(this ServicesContainer services);

}

在ASP.NET WebAPI中有一个GlobalConfiguration,其实它并不是WebAPI的一部分。WebAPI只是一个独立的框架。它需要寄宿在别的应用程序下才能运行。寄宿模式则分为两种WebHost,SelfHost，WebHost是针对Web程序的寄宿。因为本系列只讨论ASP.Net下的WebAPI，所以只简单讲一下WebHost模式。

ASP.NET WebAPI中引用了程序集System.Web.Http.WebHost,GlobalConfiguration就在该程序集下.它包含了一个HttpConfiguration属性.还一个配置HttpConfiguration的方法

另外还有一个HttServer

另外在ApiController的很多属性都能找到HttpConfiguraiton
Configuration

ControllerContext.Configuration

RequestContext.Configuration

这些HttpConfiguration都来自对GlobalConfiguration.Configuration的引用.

DependencyResolver

WebAPI为我们提供了一个Ioc框架,即DependencyResolver

public interface IDependencyResolver : IDependencyScope, IDisposable

{

IDependencyScope BeginScope();

}

public interface IDependencyScope : IDisposable

{

object GetService(Type serviceType);

IEnumerable<object> GetServices(Type serviceType);

}

IDependencyResolver也继承了IDependencyScope,所以我们可以将IDependencyScope视为依赖的上下文.

在WebAPI中DependencyResolver并没有像其它组件一样注册在ServicesContainer中,而是直接注册在HttpConfiguration中(DependencyResolver属性).

别个HttpRequestMessage中也有一扩展方法GetDependencyScope来获取DependencyScope,该方法获取的是HttpRequestMessage的Properties的DependencyResolver,这里的DependencyResolver也来自HttpConfiguration.

在WebAPI中也定义了一个EmptyResolver,它只是一个空的Resolver,所以在WebAPI默认就是采用直接反射方式.

源码

Github: https://github.com/BarlowDu/WebAPI (API_8)