依赖项注入不适用于Owin自托管的Web Api 2和Autofac [英] Dependency injection not working with Owin self-hosted Web Api 2 and Autofac

问题描述

我正在使用Web Api 2，Owin和Autofac站起来，请提供一些指导.

I'm finding my feet with Web Api 2, Owin and Autofac and need some guidance, please.

概述
我有一个Owin自托管Web Api，它使用Autofac进行IoC和依赖注入.该项目是一个充当服务的控制台应用程序，这意味着它可以停止和启动.我有一个带有两个构造函数的Authentication控制器:一个没有参数，另一个则注入一个存储库.

Overview
I have an Owin self-hosted Web Api that uses Autofac for IoC and dependency injection. The project is a console app acting like a service, meaning it can be stopped and started. I have an Authentication controller with two constructors: one parameter-less and the other injects a repository.

问题
当我运行该服务并调用api时，将调用我的无参数构造函数，并且永远不会注入我的存储库(_repository = null).

Problem
When I run the service and call the api, my parameter-less constructor is called and my repository never gets injected (_repository = null).

研究
我已经做了相当多的研究，并在Github上找到了一些有用的项目，这些项目已经复制到了发球台上，但是我却错过了很大一部分难题. 这很有帮助，但没有解决我的问题.我在堆栈溢出和Dane Sparza上阅读了这个问题有一个很好的演示项目，但我找不到明确的解决方案.问题不在于自托管，而是依赖注入.

Research
I've done a fair bit of research and found some helpful projects on Github, which I replicated to the tee but I'm missing a big part of the puzzle. This was helpful but didn't solve my problem. I read this question on Stack Overflow and Dane Sparza had a nice demo project but I couldn't find a clear solution. The problem is not the self-hosting but the dependency injection.

我的代码(为便于解释，请细化)

My code (thinned out for explanation)

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        HttpConfiguration config = new HttpConfiguration();

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        var json = config.Formatters.JsonFormatter;
        json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects;
        config.Formatters.Remove(config.Formatters.XmlFormatter);

        var connectioninfo = ConnectionInfo.FromAppConfig("mongodb");

        var builder = new ContainerBuilder();                                    // Create the container builder.
        builder.RegisterApiControllers(Assembly.GetExecutingAssembly());         // Register the Web API controllers.
        builder.Register(c => new Logger()).As<ILogger>().InstancePerRequest();  // Register a logger service to be used by the controller and middleware.
        builder.RegisterType<AuthenticationRepository>().As<IAuthenticationRepository>().WithParameter(new NamedParameter("connectionInfo", connectioninfo)).InstancePerRequest();

        var container = builder.Build();

        var resolver = new AutofacWebApiDependencyResolver(container);           // Create an assign a dependency resolver for Web API to use.
        GlobalConfiguration.Configuration.DependencyResolver = resolver;         // Configure Web API with the dependency resolver

        app.UseCors(CorsOptions.AllowAll);  
        app.UseWebApi(config);
        app.UseAutofacWebApi(config);  // Make sure the Autofac lifetime scope is passed to Web API.
    }

Program.cs

Program.cs

 static void Main(string[] args)
    {           
        var service = new ApiService(typeof(Program), args);

        var baseAddress = "http://localhost:9000/";
        IDisposable _server = null;

        service.Run(
           delegate()
           {
               _server = WebApp.Start<Startup>(url: baseAddress);
           },
           delegate()
           {
               if (_server != null)
               {
                   _server.Dispose();
               }
           }
       );
    }

ApiController

ApiController

public class AuthenticationController : ApiController
{
    private IAuthenticationRepository _repository;

    public AuthenticationController() { }

    public AuthenticationController(IAuthenticationRepository repository)
    {
        _repository = repository;
    }

    [AllowAnonymous]
    public IHttpActionResult Authenticate(string name, string password)
    {
        if (_repository == null)
            return BadRequest("User repository is null.");

        var valid = _repository.AuthenticateUser(name, password);
        return Ok(valid);
    }
}

推荐答案

您应该使用HttpConfiguration引导OWIN. 所以，这个:

You should be using the HttpConfiguration with which you're bootstrapping OWIN everywhere. So, this:

GlobalConfiguration.Configuration.DependencyResolver = resolver;

应成为:

config.DependencyResolver = resolver;

除此之外，一切看起来都不错. Api控制器已注册，尽管您没有给它们指定范围.不知道在Autofac中，作用域范围默认为对控制器的按请求作用域，还是根本没有按请求作用域的概念(我知道LightInject就是这样).

Other than that, everything looks good. Api controllers are registered, although you're not giving them a scope. Not sure if in Autofac scoping defaults to per-request for controllers or if it has the notion of per-request scoping at all (I know that LightInject has it).

环顾四周，我认为您遵循了Autofac的Google代码存储库中的示例，该示例确实使用了GlobalConfiguration.相反，如果您查看 GitHub示例 ，这有点不同.尝试根据此进行更改.包括这个:

Looking around, I think you followed the example on the Google Code repo for Autofac, which indeed uses GlobalConfiguration. Instead, if you look at the GitHub example, it is a bit different. Try to make the changes according to this. Including this:

// This should be the first middleware added to the IAppBuilder.
app.UseAutofacMiddleware(container);

---

2016年更新

我上面所说的内容仍然适用，但是Autofac的文档有一些其他优点(感谢Brad):

What I said above still applies, but something extra from Autofac's docs (thanks Brad):

OWIN集成中的一个常见错误是使用 GlobalConfiguration.Configuration.在OWIN中，您可以创建 从头开始配置.你不应该参考 GlobalConfiguration.Configuration在使用OWIN的任何地方 整合.

A common error in OWIN integration is use of the GlobalConfiguration.Configuration. In OWIN you create the configuration from scratch. You should not reference GlobalConfiguration.Configuration anywhere when using the OWIN integration.

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