将HttpRequestMessage转换为OwinRequest和OwinResponse转换为HttpResponseMessage

Question

我有一个Web API消息处理程序MyHandler,我想在OWIN管道中作为中间件运行.所以像这样配置处理程序.

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        app.UseHttpMessageHandler(new MyHandler());

        HttpConfiguration config = new HttpConfiguration();

        config.Routes.MapHttpRoute(
            "DefaultWebApi",
                "{controller}/{id}",
                    new { id = RouteParameter.Optional });

        app.UseWebApi(config);
    }
}

处理程序非常简单,什么都不做.

public class MyHandler : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(
             HttpRequestMessage request, CancellationToken cancellationToken)
    { // <--- breakpoint here

        var response = await base.SendAsync(request, cancellationToken);
        return response;
    }
}

我在里面放了一个断点SendAsync,它确实打破但是下面的base.SendAsync炸弹默默地看着我A first chance exception of type 'System.InvalidOperationException' occurred in System.Net.Http.dll.

我可以很容易地添加MyHandler到config.MessageHandlers它,它将在Web API管道中运行完美,但这不是我想要做的.我想MyHandler在OWIN管道中运行.这有可能吗？它应该是.否则,UseHttpMessageHandler我猜是没有必要使用扩展方法.只是我想不出办法做我想做的事.

Answer 1

是的，这种体验需要改进，因为异常被默默地忽略了。

对于上面的场景，您需要派生而HttpMessageHandler不是因为DelegatingHandler委托处理程序会尝试将请求委托给其后的处理程序。（示例：异常提到Message=The inner handler has not been assigned）

例如，以下内容可以工作：

appBuilder.UseHttpMessageHandler(new MyNonDelegatingHandler());

public class MyNonDelegatingHandler : HttpMessageHandler
{
    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        HttpResponseMessage response = new HttpResponseMessage();
        response.Content = new StringContent("Hello!");

        return Task.FromResult<HttpResponseMessage>(response);
    }
}

为了创建处理程序链，您可以执行以下操作：

appBuilder.UseHttpMessageHandler(HttpClientFactory.CreatePipeline(innerHandler: new MyNonDelegatingMessageHandler(),
           handlers: new DelegatingHandler[] { new DelegatingHandlerA(), new DelegatingHandlerB() }));