OWIN 自宿主模式WebApi项目，WebApi层作为单独类库供OWIN调用

OWIN是Open Web Server Interface for .NET的首字母缩写，他的定义如下：

OWIN在.NET Web Servers与Web Application之间定义了一套标准接口，OWIN的目标是用于解耦Web Server和Web Application。基于此标准，鼓励开发者开发简单、灵活的模块，从而推进.NET Web Development开源生态系统的发展。

为什么我们需要OWIN

过去，IIS作为.NET开发者来说是最常用的Web Server（没有之一），源于微软产品的紧耦合关系，我们不得不将Website、Web Application、Web API等部署在IIS上，事实上在2010年前并没有什么不妥，但随着近些年来Web的发展，特别是移动互联网飞速发展，IIS作为Web Server已经暴露出他的不足了。主要体现在两个方面，ASP.NET (System.Web)紧耦合IIS，IIS紧耦合OS，这就意味着，我们的Web Framework必须部署在微软的操作系统上，难以跨平台。

 

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OWIN是什么？在本文里面就不进行赘述，网上有很多介绍OWIN的信息以及优缺点的博文，这里可以给几个链接大家进行自行参考：

1、http://www.cnblogs.com/dudu/p/what-is-owin.html

2、http://blog.csdn.net/hk_5788/article/details/51607211

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下面我们重点介绍我在搭建OWIN自宿主平台的过程，对于我是学习的过程，对于想要接触他的大家来说，也是一种帮助。

 

很多人搭建的OWIN+WebApi项目都是写在一个项目中的，我个人为了代码的隔离，将控制器层写在了另外一个项目中，这样有助于后期大型框架的形成。

下面是搭建步骤：

1、首先新建一个控制台应用程序和一个.NETFramework类库项目，控制台引用类库项目。

项目结构如下图所示：

OWIN.WebApi WebApi层

OWIN.WebApi.Sv WebApi服务层，将要作为启动项！

2、控制台项目使用NuGet引用需要的类库：

　　OWIN

　　Microsoft.Owin.Hosting

　　Microsoft.Owin.Host.HttpListener

　　Microsoct.AspNet.WebApi.Owin

　　这里需要手动从WebApi项目里面找到System.Web.Web,System.Net.Http等Web类库进行引用。

　　OWIN.WebApi.Srv层的引用情况（我这里有跨域配置，不需要的请忽略）

　　

　　在OWIN.WebApi层，我们需要同样引用Web的类库，我们才可以在WebApi项目控制器层继承自ApiController

 　  OWIN.WebApi层的引用情况（我这里有跨域配置，不需要的请忽略）

　　

 3、因为WebApi层要分开类库项目写，所以这里比一般的OWIN要多一些配置，在我项目的OWIN.WebApi层的config目录下，我新建了一个Global.cs类，里面的代码是对控制器的解析，代码展示如下：

 using System.Web.Http;
 using System.Web.Http.Dispatcher;
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Web.Http.Controllers;
 
 namespace OWIN.WebApi.config
 {
     public class WebApiApplication : System.Web.HttpApplication
     {
         protected void Application_Start()
         {
             //ignore the xml return it`s setting let json return only
             GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
             GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
 
             GlobalConfiguration.Configuration.Services.Replace(typeof(IHttpControllerSelector),
             new WebApiControllerSelector(GlobalConfiguration.Configuration));
         }
     }
     /// <summary>
     /// the WebApiControllerSelector
     /// author:qixiao
     /// time:2017-1-31 19:24:32
     /// </summary>
     public class WebApiControllerSelector : DefaultHttpControllerSelector
     {
         private const string NamespaceRouteVariableName = "Namespace";
         private readonly HttpConfiguration _configuration;
         private readonly Lazy<ConcurrentDictionary<string, Type>> _apiControllerCache;
 
         public WebApiControllerSelector(HttpConfiguration configuration)
             : base(configuration)
         {
             _configuration = configuration;
             _apiControllerCache = new Lazy<ConcurrentDictionary<string, Type>>(
                 new Func<ConcurrentDictionary<string, Type>>(InitializeApiControllerCache));
         }
 
         private ConcurrentDictionary<string, Type> InitializeApiControllerCache()
         {
             IAssembliesResolver assembliesResolver = this._configuration.Services.GetAssembliesResolver();
             var types = this._configuration.Services.GetHttpControllerTypeResolver()
                 .GetControllerTypes(assembliesResolver).ToDictionary(t => t.FullName, t => t);
 
             return new ConcurrentDictionary<string, Type>(types);
         }
 
         public IEnumerable<string> GetControllerFullName(HttpRequestMessage request, string controllerName)
         {
             object namespaceName;
             var data = request.GetRouteData();
             IEnumerable<string> keys = _apiControllerCache.Value.ToDictionary<KeyValuePair<string, Type>, string, Type>(t => t.Key,
                     t => t.Value, StringComparer.CurrentCultureIgnoreCase).Keys.ToList();
 
             if (!data.Values.TryGetValue(NamespaceRouteVariableName, out namespaceName))
             {
                 return from k in keys
                        where k.EndsWith(string.Format(".{0}{1}", controllerName,
                        DefaultHttpControllerSelector.ControllerSuffix), StringComparison.CurrentCultureIgnoreCase)
                        select k;
             }
 
             string[] namespaces = (string[])namespaceName;
             return from n in namespaces
                    join k in keys on string.Format("{0}.{1}{2}", n, controllerName,
                    DefaultHttpControllerSelector.ControllerSuffix).ToLower() equals k.ToLower()
                    select k;
         }
 
         public override HttpControllerDescriptor SelectController(HttpRequestMessage request)
         {
             Type type;
             if (request == null)
             {
                 throw new ArgumentNullException("request");
             }
             string controllerName = this.GetControllerName(request);
             if (string.IsNullOrEmpty(controllerName))
             {
                 throw new HttpResponseException(request.CreateErrorResponse(HttpStatusCode.NotFound,
                     string.Format("No route providing a controller name was found to match request URI '{0}'", new object[] { request.RequestUri })));
             }
             IEnumerable<string> fullNames = GetControllerFullName(request, controllerName);
             )
             {
                 throw new HttpResponseException(request.CreateErrorResponse(HttpStatusCode.NotFound,
                         string.Format("No route providing a controller name was found to match request URI '{0}'", new object[] { request.RequestUri })));
             }
 
             if (this._apiControllerCache.Value.TryGetValue(fullNames.First(), out type))
             {
                 return new HttpControllerDescriptor(_configuration, controllerName, type);
             }
             throw new HttpResponseException(request.CreateErrorResponse(HttpStatusCode.NotFound,
                 string.Format("No route providing a controller name was found to match request URI '{0}'", new object[] { request.RequestUri })));
         }
     }
 }

4、在OWIN.WebApi.Srv层里面新建AppStart.cs类，并且写如下代码：

 using Microsoft.Owin.Hosting;
 using System;
 using Owin;
 using System.Web.Http;
 using System.Web.Http.Dispatcher;
 using QX_Frame.App.WebApi.Extends;
 using System.Web.Http.Cors;
 
 namespace OWIN.WebApi.Srv
 {
     class AppStart
     {
         static void Main(string[] args)
         {
             //string baseAddress = "http://localhost:3999/";    //localhost visit
             string baseAddress = "http://+:3999/";              //all internet environment visit
             try
             {
                 WebApp.Start<StartUp>(url: baseAddress);
                 Console.WriteLine("BaseIpAddress is " + baseAddress);
                 Console.WriteLine("\nApplication Started !");
             }
             catch (Exception ex)
             {
                 Console.WriteLine(ex.ToString());
             }
 
             for (;;)
             {
                 Console.ReadLine();
             }
         }
     }
     //the start up configuration
     class StartUp
     {
         public void Configuration(IAppBuilder appBuilder)
         {
             HttpConfiguration config = new HttpConfiguration();
 
             // Web API configuration and services
             //跨域配置 //need reference from nuget
             config.EnableCors(new EnableCorsAttribute("*", "*", "*"));
             //enabing attribute routing
             config.MapHttpAttributeRoutes();
             // Web API Convention-based routing.
             config.Routes.MapHttpRoute(
                 name: "DefaultApi",
                 routeTemplate: "api/{controller}/{id}",
                 defaults: new { id = RouteParameter.Optional },
                 namespaces: new string[] { "OWIN.WebApi" }
             );
             config.Services.Replace(typeof(IHttpControllerSelector), new OWIN.WebApi.config.WebApiControllerSelector(config));
 
             //if config the global filter input there need not write the attributes
             //config.Filters.Add(new App.Web.Filters.ExceptionAttribute_DG());
 
             //new ClassRegisters(); //register ioc menbers
 
             appBuilder.UseWebApi(config);
         }
     }
 }

里面对地址进行了配置，当然可以根据需求自行配置，显示信息也进行了适当的展示，需要说明的一点是，我这里进行了跨域的配置，没有配置或者是不需要的请注释掉并忽略！

这里需要注意的是第53行，这里引用的是刚才的OWIN.WebApi层的Global.cs里面的类，请对照上述两段代码进行查找。

这行是关键，有了这行，程序才可以扫描到WebApi层的Controller。好了，我们进行Controller的书写。

5、在OWIN.WebApi层进行控制器类的编写，这里随意，我只在这里列出我的例子。

 using QX_Frame.App.WebApi;
 using QX_Frame.Helper_DG;
 using System.Web.Http;
 
 namespace OWIN.WebApi
 {
     /*
      * author:qixiao
      * time:2017-2-27 10:32:57
      **/
     public class Test1Controller:ApiController
     {
         //access http://localhost:3999/api/Test1  get method
         public IHttpActionResult GetTest()
         {
             //throw new Exception_DG("login id , pwd", "argumets can not be null", 11111, 2222);
             return Json(new { IsSuccess = true, Msg = "this is get method" });
         }
         //access http://localhost:3999/api/Test1  post method
         public IHttpActionResult PostTest(dynamic queryData)
         {
             return Json(new { IsSuccess = true, Msg = "this is post method",Data=queryData });
         }
         //access http://localhost:3999/api/Test1  put method
         public IHttpActionResult PutTest()
         {
             return Json(new { IsSuccess = true, Msg = "this is put method" });
         }
         //access http://localhost:3999/api/Test1  delete method
         public IHttpActionResult DeleteTest()
         {
             return Json(new { IsSuccess = true, Msg = "this is delete method" });
         }
     }
 }

这里我是用的是RESTFull风格的WebApi控制器接口。

然后我们可以进行试运行：

服务启动成功！

测试通过，我们可以尽情地探索后续开发步骤！