Autofac循环依赖

Question

当我尝试用Autofac构建以下代码时，我得到一个循环依赖异常：

        builder.RegisterType<Session>().As<ISession>();
        builder.RegisterType<SFEventStore>().As<IEventStore>();
        builder.RegisterType<MemoryCache>().As<ICache>();
        builder.Register(c =>
        {
            return new CacheRepository(new Repository(c.Resolve<IEventStore>()), c.Resolve<IEventStore>(), c.Resolve<ICache>());

        })
        .As<IRepository>();

问题出在IRepository，它解析为CacheRepository，而CacheRepository依赖于IRepository：

public CacheRepository(IRepository repository, IEventStore eventStore, ICache cache);

存储库在其构造函数中接受一个IEventStore：

    public class Repository : IRepository
    {
        private readonly IEventStore _eventStore;

        public Repository(IEventStore eventStore)
        {
            _eventStore = eventStore ?? throw new ArgumentNullException(nameof(eventStore));
        }
    }

CacheRepository遵循装饰器模式，并将功能添加到存储库：

public class CacheRepository : IRepository
    {
        private readonly IRepository _repository;
        private readonly IEventStore _eventStore;
        private readonly ICache _cache;

        public CacheRepository(IRepository repository, IEventStore eventStore, ICache cache)
        {
            _repository = repository ?? throw new ArgumentNullException(nameof(repository));
            _eventStore = eventStore ?? throw new ArgumentNullException(nameof(eventStore));
            _cache = cache ?? throw new ArgumentNullException(nameof(cache));

        }

因此，即使我在Autofac builder方法中新建了一个存储库，Autofac仍然尝试在CacheRepository构造函数中解析IRepository，该构造函数解析为CacheRepository。因此出现了循环依赖。

尝试使用Autofac Decorator解决此问题，如下所示：

        builder.RegisterType<Session>().As<ISession>();
        builder.RegisterType<SFEventStore>().As<IEventStore>();
        builder.RegisterType<MemoryCache>().As<ICache>();
        builder.Register(c =>
        {
            return new Repository(c.Resolve<IEventStore>());
        })
        .Named<IRepository>("implementor");

        builder.RegisterDecorator<IRepository>(
            (c, inner) => new CacheRepository(inner, c.Resolve<IEventStore>(), c.Resolve<ICache>()),
            fromKey: "implementor");

但没那么走运。还给出了循环依赖！

该链从解析会话开始，该会话具有以下ctor：

public Session(IRepository repository);

所以我应该得到下面的组件依赖树：

Session --> CacheRepository --> Repository --> SFEventStore

但相反，它解析为：

Session --> CacheRepository --> CacheRepository

这是堆栈跟踪：

Autofac.Core.DependencyResolutionException:检测到循环组件依赖项: AnswersBC.Command.Handlers.AddAnswerCmdHandler -> CQRSlite.Domain.Session -> CQRSlite.Cache.CacheRepository -> CQRSlite.Cache.CacheRepository。在Autofac.Core.Resolving.CircularDependencyDetector.CheckForCircularDependency(IComponentRegistration注册时，在C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line上下文的Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate()处的C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0中的Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext 0中栈1 activationStack, Int32 callDepth) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable1参数)，在Autofac.Core.Lifetime.LifetimeScope.GetOrCreateAndShare(Guid _ id处的C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line _0中的函数1 creator) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Execute() in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable_1参数)，在Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext _ context处的Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate() _ in _ C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line _0中的Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext_0中的IEnumerable_1 parameters) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable_1参数)，在Autofac.Core.Lifetime.LifetimeScope.GetOrCreateAndShare(Guid _ id处的C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line _0中的函数1 creator) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Execute() in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable_1参数)，在Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext _ context处的Autofac.Core.Activators.Reflection.ConstructorParameterBinding.Instantiate() _ in _ C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line _0中的Autofac.Core.Activators.Reflection.ReflectionActivator.ActivateInstance(IComponentContext_0中的IEnumerable_1 parameters) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable_1参数)，在Autofac.Core.Resolving.ResolveOperation.Execute(IComponentRegistration注册时的C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0中的函数1 parameters) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable1参数)，在Autofac.ResolutionExtensions.ResolveService(IComponentContext上下文中的C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0中的IEnumerable1 parameters) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0 at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable1参数，对象和实例)，服务服务，IEnumerable`1个参数)在C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Licensing\LogErrorOnInvalidLicenseBehavior.cs:line 0中，位于C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\ObjectBuilder\Autofac\AutofacObjectBuilder.cs:line 39中的NServiceBus.LoadHandlersConnector.d__1.MoveNext() (类型为typeToBuild)，位于C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\Pipeline\Incoming\LoadHandlersConnector.cs:line 37中

Answer 1

你所描述的听起来就像是装饰者模式。您有两个IRepository实现，一个包装了另一个。Autofac使用.RegisterDecorator()本机支持这一点

请参阅此处的文档，http://docs.autofac.org/en/latest/advanced/adapters-decorators.html

我相信你的“新”设置就是问题所在，请看下面的例子。

不要使用以下命令：

builder.Register(c =>
{
    return new Repository(c.Resolve<IEventStore>());
})
.Named<IRepository>("implementor");

取而代之的是：

builder.RegisterType<Repository>().Named<IRepository>("implementor");
builder.RegisterDecorator<IRepository>(
        (c, inner) => new CacheRepository(inner, c.Resolve<IEventStore>(), c.Resolve<ICache>()),
        fromKey: "implementor");

Answer 2

似乎必须对NServiceBus中的组件进行一些配置：

        nsbEndpointConfig.RegisterComponents(registration: configureComponents =>
        {
            configureComponents.ConfigureComponent<Session>(DependencyLifecycle.InstancePerUnitOfWork);
            configureComponents.ConfigureComponent<SFEventStore>(DependencyLifecycle.InstancePerUnitOfWork);
            configureComponents.ConfigureComponent<MemoryCache>(DependencyLifecycle.InstancePerUnitOfWork);
            configureComponents.ConfigureComponent<Repository>(DependencyLifecycle.InstancePerUnitOfWork);
            configureComponents.ConfigureComponent<CacheRepository>(DependencyLifecycle.InstancePerUnitOfWork);
        });

当我省略这个配置时，没有检测到循环依赖。但是，我在这里所做的只是设置生命周期范围。