带有OWIN WebApi自主机的Unity的每个请求生存期

Question

我正在使用OWIN自托管构建WebApi服务（可在控制台模式下运行或作为Windows服务运行-最终部署为服务，控制台模式用于调试/开发）。我在Unity注入的每个请求生命周期中遇到问题。

我以前已经构建了其他部署为IIS WebApi的服务；我将Unity Mvc nuget与基本的Unity nuget一起添加，按照说明进行操作，一切都可以。

在OWIN自托管环境中，默认类型注册和ContainerControlledLifetimeManager注册没有问题，但是PerRequestLifetimeManager无法工作。一方面，UnityMvcActivator不会像在IIS中那样在OWIN自托管下自动启动。如果在执行此操作时显式调用UnityMvcActivator.Start，则尝试使用PerRequestLifetimeManager注册的类型的解析会导致InvalidOperationException，并显示以下消息：

PerRequestLifetimeManager只能在HTTP请求的上下文中使用。此错误的可能原因是在非ASP.NET应用程序上使用生命周期管理器，或者在与适当的同步上下文无关的线程中使用它。 。

PerRequestLifetimeManager是否可以与OWIN自宿主一起使用，还是取决于IIS？如果它可以在OWIN自宿主下运行，如何使UnityMvcActivator正常启动并注册我的注入类型？如果PerRequestLifetimeManager与OWIN自托管主机不兼容，该如何在每个请求的生存期内注册类型？

UnityConfig的部分：

    public static void RegisterTypes(IUnityContainer container)
    {
        // NOTE: To load from web.config uncomment the line below.
        // Make sure to add a Unity.Configuration to the using statements.
        // container.LoadConfiguration();

        // TODO: Register your type's mappings here.
        // container.RegisterType<IProductRepository, ProductRepository>();

        // My test registration:
        container.RegisterType<ITestService, TestService>(new PerRequestLifetimeManager());
    }

UnityMvcActivator（如NuGet所提供，但未注释的行除外）：

[assembly: WebActivatorEx.PreApplicationStartMethod(typeof(Accounting.Service.UnityMvcActivator), nameof(Accounting.Service.UnityMvcActivator.Start))]
[assembly: WebActivatorEx.ApplicationShutdownMethod(typeof(Accounting.Service.UnityMvcActivator), nameof(Accounting.Service.UnityMvcActivator.Shutdown))]

namespace Accounting.Service
{
    /// <summary>
    /// Provides the bootstrapping for integrating Unity with ASP.NET MVC.
    /// </summary>
    public static class UnityMvcActivator
    {
        /// <summary>
        /// Integrates Unity when the application starts.
        /// </summary>
        public static void Start() 
        {
            var container = UnityConfig.Container;

            FilterProviders.Providers.Remove(FilterProviders.Providers.OfType<FilterAttributeFilterProvider>().First());
            FilterProviders.Providers.Add(new UnityFilterAttributeFilterProvider(container));

            DependencyResolver.SetResolver(new UnityDependencyResolver(container));

            // TODO: Uncomment if you want to use PerRequestLifetimeManager
            Microsoft.Web.Infrastructure.DynamicModuleHelper.DynamicModuleUtility.RegisterModule(typeof(UnityPerRequestHttpModule));
        }

        /// <summary>
        /// Disposes the Unity container when the application is shut down.
        /// </summary>
        public static void Shutdown()
        {
            UnityConfig.Container.Dispose();
        }
    }
}

编辑

[MVC PerRequestLifetimeManager似乎无法在我尝试使用的上下文中工作，但是我已经设计出我认为使用OWIN中间件的解决方法如下：

public class PerRequestMiddleware : OwinMiddleware
{
    [ThreadStatic] static Dictionary<Type, object> _instances;

    public PerRequestMiddleware(OwinMiddleware next) : base(next)
    {
    }

    public override async Task Invoke(IOwinContext context)
    {
        _instances = null;

        await Next.Invoke(context);

        if (_instances != null)
        {
            foreach (var disposable in _instances.Values.OfType<IDisposable>())
            {
                disposable.Dispose();
            }
        }
    }

    public static T GetInstance<T>(Func<T> constructor)
    {
        if (_instances == null)
        {
            _instances = new Dictionary<Type, object>();
        }

        var type = typeof(T);

        if (!_instances.TryGetValue(type, out var instance))
        {
            instance = constructor();
            _instances[type] = instance;
        }

        return (T)instance;
    }
}

而不是按类型注册，我这样注册工厂：

public static class UnityConfig
{
    #region Unity Container
    private static Lazy<IUnityContainer> container =
      new Lazy<IUnityContainer>(() =>
      {
          var container = new UnityContainer();
          RegisterTypes(container);
          return container;
      });

    /// <summary>
    /// Configured Unity Container.
    /// </summary>
    public static IUnityContainer Container => container.Value;
    #endregion

    /// <summary>
    /// Registers the type mappings with the Unity container.
    /// </summary>
    /// <param name="container">The unity container to configure.</param>
    /// <remarks>
    /// There is no need to register concrete types such as controllers or
    /// API controllers (unless you want to change the defaults), as Unity
    /// allows resolving a concrete type even if it was not previously
    /// registered.
    /// </remarks>
    public static void RegisterTypes(IUnityContainer container)
    {
        // NOTE: To load from web.config uncomment the line below.
        // Make sure to add a Unity.Configuration to the using statements.
        // container.LoadConfiguration();

        // TODO: Register your type's mappings here.
        // container.RegisterType<IProductRepository, ProductRepository>();

        container.RegisterFactory<ITestService>(c => PerRequestMiddleware.GetInstance(() => new TestService()));
    }
}

我现在的问题是：我的解决方法是否包含任何缺陷或弱点？

Answer 1

“解决方法”效果很好。

解决了Github OwinPerRequestUnityMiddleware上here项目中的问题。

感谢您分享代码！