ASP.NET WebAPI 08 Message,HttpConfiguration,DependencyResolver

时间：2022-02-14 13:39:43

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)

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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.

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)

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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

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
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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.

DependencyResolver

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.

源码

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

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