Question

这是我的代码

public interface ICommandHandler<T>
{
    void Handle(T command);
}

public class CreateUserCommandHandler : ICommandHandler<CreateUserCommand>
{
    public void Handle(CreateUserCommand command)
    {
        // do something with the command
    }
}

public class LoggingCommandDecorator<TCommand> : ICommandHandler<TCommand>
{
    private readonly ICommandHandler<TCommand> _commandHandler;

    public LoggingCommandDecorator(ICommandHandler<TCommand> commandHandler)
    {
        _commandHandler = commandHandler;
    }

    public void Handle(TCommand command)
    {
        Debug.WriteLine("Logging...");

        _commandHandler.Handle(command);
    }
}

这是我的注册：

private void SetupAutofac()
{
    var builder = new ContainerBuilder();

    // Register your MVC controllers.
    builder.RegisterControllers(typeof(WebApiApplication).Assembly);

    // OPTIONAL: Register model binders that require DI.
    builder.RegisterModelBinders(Assembly.GetExecutingAssembly());
    builder.RegisterModelBinderProvider();

    var assemblies = AppDomain.CurrentDomain.GetAssemblies();
    builder.RegisterAssemblyTypes(assemblies)
            .As(o => o.GetInterfaces()
            .Where(i => i.IsClosedTypeOf(typeof(ICommandHandler<>)))
            .Select(i => new KeyedService("Handler", i)));

    builder.RegisterGenericDecorator(typeof(LoggingCommandDecorator<>),
                            typeof(ICommandHandler<>),
                            "Handler", "DecoratedHandler");


    var container = builder.Build();

    DependencyResolver.SetResolver(new AutofacDependencyResolver(container));
}

当我运行此代码时，我得到以下异常：

没有找到的构造函数＆＃39; Autofac.Core.Activators.Reflection.DefaultConstructorFinder＆＃39;在类型上＆＃39; AspectDemo.Controllers.HomeController＆＃39;可以用。调用可用的服务和参数：无法解析参数＆＃39; {AspectDemo.Business.ICommandHandler {1}} 1 [AspectDemo.Business.Users.CreateUserCommand]）＆＃39;

当我使用以下作为我的注册时，我没有得到例外，但我也没有任何装饰者。

1[AspectDemo.Business.Users.CreateUserCommand]
  createUserHandler' of constructor 'Void
  .ctor(AspectDemo.Business.ICommandHandler

我需要做什么才能使用装饰器？

注意：现在我只使用一个装饰器，但最后我觉得我有大约4-5个装饰器。

Answer 1

当您使用toKey方法的RegisterGenericDecorator参数时，会导致命名注册，因此您必须解析名为ICommandHandler的

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Handler",
    toKey : "DecoratedHandler");

然后你可以像这样解决它：

container.ResolveKeyed<ICommandHandler<CreateUserCommand>>("DecoratedHandler");

toKey参数是可选的：

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Handler");

然后你可以像这样解决它：

container.Resolve<ICommandHandler<CreateUserCommand>>();

当你有中间装饰时，toKey很有用：

builder.RegisterGenericDecorator(
    typeof(LoggingCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Original", 
    toKey : "Logging");

builder.RegisterGenericDecorator(
    typeof(AuthorizationCommandDecorator<>), 
    typeof(ICommandHandler<>), 
    fromKey : "Logging");

在这种情况下，ICommandHandler<CreateUserCommand>将由LoggingCommandDecorator<>和AuthorizationCommandDecorator<>装饰

使用RegisterAssemblyTypes时如何使用Autofac注册装饰器？

1 个答案: