Owin Middleware如何在IIS集成管道中执行

Owin Middleware Components(OMCs)

通过安装Install-Package Microsoft.Owin.Host.SystemWeb

可以让OMCs在IIS集成管道下工作

在IIS集成管道里，这个request pipeline 包含HttpModules关联到一组预定义的管道事件，例如

BeginRequest, AuthenticateRequest, AuthorizeRequest,等

如果我们将OMC和HttpModule进行比较，OMC也和HttpModule一样,必须要被注册到一个恰当的预定义的管道事件里，比如下面的这个Httpmodule，

当一个请求来到AuthenticateRequest阶段时，MyModule会被调用

public class MyModule : IHttpModule

{

    public void Dispose()

    {

        //clean-up code here.

    }

    public void Init(HttpApplication context)

    {

        // An example of how you can handle AuthenticateRequest events.

        context.AuthenticateRequest += ctx_AuthRequest;

    }

    void ctx_AuthRequest(object sender, EventArgs e)

    {

        // Handle event.

    }

}

为了使OMC取参与和HttpModule相同的基于事件的执行顺序，Katana运行时代码扫描Startup配置，并且把每个OMC关联到某个集成管道事件里，

比如下面的配置：

using System;

using System.Threading.Tasks;

using Microsoft.Owin;

using Owin;

using System.Web;

using System.IO;

using Microsoft.Owin.Extensions;

[assembly: OwinStartup(typeof(owin2.Startup))]

namespace owin2

{

    public class Startup

    {

        public void Configuration(IAppBuilder app)

        {

            app.Use((context, next) =>

            {

                PrintCurrentIntegratedPipelineStage(context, "Middleware 1");

                return next.Invoke();

            });

            app.Use((context, next) =>

            {

                PrintCurrentIntegratedPipelineStage(context, "2nd MW");

                return next.Invoke();

            });

            app.Run(context =>

            {

                PrintCurrentIntegratedPipelineStage(context, "3rd MW");

                return context.Response.WriteAsync("Hello world");

            });

        }

        private void PrintCurrentIntegratedPipelineStage(IOwinContext context, string msg)

        {

            var currentIntegratedpipelineStage = HttpContext.Current.CurrentNotification;

            context.Get<TextWriter>("host.TraceOutput").WriteLine(

                "Current IIS event: " + currentIntegratedpipelineStage

                + " Msg: " + msg);

        }

    }

}

输出如下：

Current IIS event: PreExecuteRequestHandler Msg: Middleware 1

Current IIS event: PreExecuteRequestHandler Msg: 2nd MW

Current IIS event: PreExecuteRequestHandler Msg: 3rd MW

可以看到Katana运行时默认映射每个OMC到IIS管道事件PreRequestHandlerExecute

你可以根据需要调整这个OMC和管道事件的这种默认关系，具体使用一个扩展方法IAppBuilder UseStageMarker()，

像下面这样：

public void Configuration(IAppBuilder app)

{

    app.Use((context, next) =>

    {

        PrintCurrentIntegratedPipelineStage(context, "Middleware 1");

        return next.Invoke();

    });

    app.Use((context, next) =>

    {

        PrintCurrentIntegratedPipelineStage(context, "2nd MW");

        return next.Invoke();

    });

    app.UseStageMarker(PipelineStage.Authenticate);

    app.Run(context =>

    {

        PrintCurrentIntegratedPipelineStage(context, "3rd MW");

        return context.Response.WriteAsync("Hello world");

    });

    app.UseStageMarker(PipelineStage.ResolveCache);

}

输出如下：

Current IIS event: AuthenticateRequest Msg: Middleware 1

Current IIS event: AuthenticateRequest Msg: 2nd MW

Current IIS event: ResolveRequestCache Msg: 3rd MW

https://docs.microsoft.com/en-us/aspnet/aspnet/overview/owin-and-katana/owin-middleware-in-the-iis-integrated-pipeline

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Owin Middleware如何在IIS集成管道中执行

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