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。
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)
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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.
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)
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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在WebAPI大概有如下几个作用：
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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。
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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);} |
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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.
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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
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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.
WebAPI为我们提供了一个Ioc框架,即DependencyResolver
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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.
Github: https://github.com/BarlowDu/WebAPI (API_8)
ASP.NET WebAPI 08 Message,HttpConfiguration,DependencyResolver
原文：http://www.cnblogs.com/shiningrise/p/5585927.html