Web API 源码剖析之默认配置（HttpConfiguration）

快来打我* 2021-06-26 16:06 355阅读 0赞

我们在上一节讲述了全局配置和初始化。本节我们将就全局配置的`Configuration`只读属性进行展开，她是一个类型为`HttpConfiguration`。 它在`Web Api` 主要为整个`API` 做一些最基础的工作，比如定义默认

1.  路由表（`Routes`）
2.  过滤器（`Filters`）
3.  默认消息处理程序（`MessageHandlers`）
4.  属性字典（`Properties`）
5.  依赖注入解耦器（`DependencyResolver`）
6.  错误处理策略（`IncludeErrorDetailPolicy`）
7.  服务（`Services`，这里的服务是之为`Web Api` 框架的服务对应的接口和实现）
8.  媒体格式程序（`Formatters`）
9.  参数绑定规则（`ParameterBindingRules`）。

以上 就是配置的属性。 接下来将就部分属性展开。

## `Formatters` ##

默认格式化程序，是一个`MediaTypeFormatterCollection`类型。

API 里定义4个默认格式：

1.  `JsonMediaTypeFormatter`：对应的是用来处理请求头是`application/json`或`text/json`格式，
2.  `XmlMediaTypeFormatter`：对应的是用来处理请求头是`application/xml`格式
3.  `FormUrlEncodedMediaTypeFormatter`:对应的是用来处理请求头是`application/x-www-form-urlencoded`，
4.  `JQueryMvcFormUrlEncodedFormatter`

## Services ##

默认服务定义如下：

public DefaultServices(HttpConfiguration configuration) 
           {  
               if (configuration == null) 
               {  
                   throw Error.ArgumentNull("configuration"); 
               }
    
               _configuration = configuration;
    
               // Initialize the dictionary with all known service types, even if the list for that service type is 
               // empty, because we will throw if the developer tries to read or write unsupported types.
    
               SetSingle<IActionValueBinder>(new DefaultActionValueBinder()); 
               SetSingle<IApiExplorer>(new ApiExplorer(configuration)); 
               SetSingle<IAssembliesResolver>(new DefaultAssembliesResolver()); 
               SetSingle<IBodyModelValidator>(new DefaultBodyModelValidator()); 
               SetSingle<IContentNegotiator>(new DefaultContentNegotiator()); 
               SetSingle<IDocumentationProvider>(null); // Missing
    
               SetMultiple<IFilterProvider>(new ConfigurationFilterProvider(), 
                                         new ActionDescriptorFilterProvider());
    
               SetSingle<IHostBufferPolicySelector>(null); 
               SetSingle<IHttpActionInvoker>(new ApiControllerActionInvoker()); 
               SetSingle<IHttpActionSelector>(new ApiControllerActionSelector()); 
               SetSingle<IHttpControllerActivator>(new DefaultHttpControllerActivator()); 
               SetSingle<IHttpControllerSelector>(new DefaultHttpControllerSelector(configuration)); 
               SetSingle<IHttpControllerTypeResolver>(new DefaultHttpControllerTypeResolver()); 
               SetSingle<ITraceManager>(new TraceManager()); 
               SetSingle<ITraceWriter>(null);
    
               // This is a priority list. So put the most common binders at the top. 
               SetMultiple<ModelBinderProvider>(new TypeConverterModelBinderProvider(), 
                                           new TypeMatchModelBinderProvider(), 
                                           new KeyValuePairModelBinderProvider(), 
                                           new ComplexModelDtoModelBinderProvider(), 
                                           new ArrayModelBinderProvider(), 
                                           new DictionaryModelBinderProvider(), 
                                           new CollectionModelBinderProvider(), 
                                           new MutableObjectModelBinderProvider()); 
               SetSingle<ModelMetadataProvider>(new DataAnnotationsModelMetadataProvider()); 
               SetMultiple<ModelValidatorProvider>(new DataAnnotationsModelValidatorProvider(), 
                                           new DataMemberModelValidatorProvider());
    
               // This is an ordered list,so put the most common providers at the top. 
               SetMultiple<ValueProviderFactory>(new QueryStringValueProviderFactory(), 
                                              new RouteDataValueProviderFactory());
    
               ModelValidatorCache validatorCache = new ModelValidatorCache(new Lazy<IEnumerable<ModelValidatorProvider>>(() => this.GetModelValidatorProviders())); 
               SetSingle<IModelValidatorCache>(validatorCache);
    
               SetSingle<IExceptionHandler>(new DefaultExceptionHandler()); 
               SetMultiple<IExceptionLogger>();
    
               _serviceTypesSingle = new HashSet<Type>(_defaultServicesSingle.Keys); 
               _serviceTypesMulti = new HashSet<Type>(_defaultServicesMulti.Keys);
    
               // Reset the caches and the known dependency scope 
               ResetCache(); 
           }

## 默认的`Action`绑定规则：`ParameterBindingRules` ##

ParameterBindingRules = DefaultActionValueBinder.GetDefaultParameterBinders();

--------------------

## web api `HttpConfiguration` ##

//设置web api configuration
    public static void Register(HttpConfiguration config)
    { 
    　　 config.Services.Replace(typeof(ITraceWriter), new NLogger());
    }
    
    //设置asp.net 应用程序 全局configuration
    GlobalConfiguration.Configuration.Services.Replace(typeof(ITraceWriter), new NLogger());
    
    //获取 全局configuration
    var writer = GlobalConfiguration.Configuration.Services.GetTraceWriter();
    
    //获取 actionContext 当前configuration
    ITraceWriter writer = actionContext.ControllerContext.Configuration.Services.GetTraceWriter();