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>
{
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;
namespace owin2
{
public>
{
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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