Using Autofac Interface Interception with IAsyncInterceptor - autofac

Question

I did use this documentation:
https://autofaccn.readthedocs.io/en/latest/advanced/interceptors.html
to implement Interface Interceptors. To handle my async calls I used the IAsyncInterceptor interface described here:
https://github.com/JSkimming/Castle.Core.AsyncInterceptor
The registration code I came up with does look like this:
builder.Register(c => new CallResultLoggerInterceptor())
.Named<IAsyncInterceptor>("log-calls");
builder.RegisterType<AppointmentService>()
.As<IAppointmentService>()
.EnableInterfaceInterceptors()
.InstancePerDependency();
where the AppointmentService has an InterceptAttribute.
[Intercept("log-calls")]
public class AppointmentService : IAppointmentService
...
When i call the containers Build() method, it throws an ComponentNotRegisteredException with the message:
The requested service 'log-calls (Castle.DynamicProxy.IInterceptor)' has not been registered. To avoid this exception, either register a component to provide the service, check for service registration using IsRegistered(), or use the ResolveOptional() method to resolve an optional dependency.
which is correct because I do not implement IInterceptor but IAsyncInterceptor. I guess the problem is the concrete implementation of EnableInterfaceInterceptors in autofac using the "wrong" extension method of the ProxyGenerator - but how can I solve this?
Cheers,
Manuel

Answer 1

You need to register a named IInterceptor for Autofac interceptors to work. You're registering an IAsyncInterceptor. That won't work.
Note Autofac has no support for this extended async interceptor extension you're using. If you want to get that to work, it'll require writing a custom adapter of some nature to get it to respond to IInterceptor.

Answer 2

You can see my answer in the issue of Castle.Core.AsyncInterceptor:
https://github.com/JSkimming/Castle.Core.AsyncInterceptor/issues/42#issuecomment-592074447
create an adapter
public class AsyncInterceptorAdaper<TAsyncInterceptor> : AsyncDeterminationInterceptor
where TAsyncInterceptor : IAsyncInterceptor
{
public AsyncInterceptorAdaper(TAsyncInterceptor asyncInterceptor)
: base(asyncInterceptor)
{ }
}
create your async interceptor
public class CallLoggerAsyncInterceptor : AsyncInterceptorBase
{
....
}
relate the interceptor to interface
[Intercept(typeof(AsyncInterceptorAdaper<CallLoggerAsyncInterceptor>))]
public interface ISomeType
register to IoC container
//register adapter
builder.RegisterGeneric(typeof(AsyncInterceptorAdaper<>));
//register async interceptor
builder.Register(c => new CallLoggerAsyncInterceptor(Console.Out));
I've made a code sample in https://github.com/wswind/aop-learn/blob/master/AutofacAsyncInterceptor

Answer 3

I've created my own extension method for registering application services.
This extension method simply prepares input parameter for castle core ProxyGenerator.
using System;
using System.Collections.Generic;
using System.Linq;
using Castle.DynamicProxy;
using Autofac;
namespace pixi.Extensions
{
public static class AutofacExtensions
{
private static readonly ProxyGenerator _proxyGenerator = new ProxyGenerator();
/// <summary>
/// Use this extension method to register default interceptors <code>UnitOfWorkInterceptor</code>
/// and <code>LoggingInterceptor</code> on your application service implementations. If you need custom
/// interceptors that are not part of infrastructure but are part of specific business module then pass
/// in those interceptors in params explicitly.
/// </summary>
/// <param name="builder"></param>
/// <param name="interceptors"></param>
/// <typeparam name="TImplementation"></typeparam>
/// <typeparam name="TService"></typeparam>
/// <exception cref="ArgumentException"></exception>
public static void RegisterApplicationService<TImplementation, TService>(this ContainerBuilder builder, params Type[] interceptors)
where TImplementation : class
{
ValidateInput<TService>(interceptors);
builder.RegisterType<TImplementation>().AsSelf();
builder.Register(c =>
{
var service = c.Resolve<TImplementation>();
var resolvedInterceptors = ResolveInterceptors<TImplementation, TService>(interceptors, c);
return (TService) _proxyGenerator.CreateInterfaceProxyWithTarget(
typeof(TService),
service,
ProxyGenerationOptions.Default,
resolvedInterceptors
);
}).As<TService>();
}
private static void ValidateInput<TService>(Type[] interceptors)
{
if (!typeof(TService).IsInterface)
throw new ArgumentException("Type must be interface");
if (interceptors.Any(i => i != typeof(IAsyncInterceptor)))
throw new ArgumentException("Only IAsyncInterceptor types are expected");
}
private static IAsyncInterceptor[] ResolveInterceptors<TImplementation, TService>(Type[] interceptors,
IComponentContext c) where TImplementation : class
{
var resolvedInterceptors = new List<IAsyncInterceptor>
{
c.Resolve<LoggingInterceptor>(),
c.Resolve<UnitOfWorkInterceptor>()
}.Concat(interceptors
.Where(i => i != typeof(UnitOfWorkInterceptor)
&& i != typeof(LoggingInterceptor))
.Select(i => (IAsyncInterceptor) c.Resolve(i))).ToArray();
return resolvedInterceptors;
}
}
}
I am using castle core for unit of work and logging hence the name UnitOfWorkInterceptor and LogginInterceptor. Change these two to your desired defaults. Default interceptors must be registered in this way:
public class SomeModule: Module
{
protected override void Load(ContainerBuilder builder)
{
builder.RegisterType<UnitOfWorkInterceptor>().AsSelf();
builder.RegisterType<LoggingInterceptor>().AsSelf();
builder.RegisterApplicationService<SampleService, ISampleService>();
builder.RegisterType<SampleRepository>().As<ISampleRepository>();
}
}
In the above code snippet I've also demonstrated the usage provided extension method. Doing it this way I get red of tag interfaces and placing extra attributes on interfaces. That way I can keep my ApplicationService interfaces free of framework/3rd party library dependencies.
I hope this helps.