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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)
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)
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：
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.
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.
ASP.NET WebAPI 08 Message,HttpConfiguration,DependencyResolver
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原文地址：http://www.cnblogs.com/gangtianci/p/4934467.html
