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：

1. 设置通信管道
2. 存储全局信息(比如Filter,Route,Formatter)
3. 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)