.NET Core 2 中使用 Castle DynamicProxy 的 Autofac 方法级拦截

Question

我目前写了一个拦截器，代码如下

public class TransactionalInterceptor : IInterceptor
{
    public void Intercept(IInvocation invocation)
    {
        using (var transaction = ...)
        {
            try
            {
                invocation.Proceed();
                transaction.Commit();

            }
            catch
            {
                transaction.Rollback();
            }
            finally
            {
                transaction.Dispose();
            }
        }

    }
}

但是当注册这个拦截器时，它将应用于所有方法。我有一个服务 class，其中的存储库注入了 CRUD 方法。我不希望为查询方法打开事务。

我读了这个 link 但我不知道如何将它应用到我的代码中 http://docs.autofac.org/en/latest/advanced/adapters-decorators.html#decorators

我不知道谁来重构我的 TransactionalInterceptor（并注册它）以在 class 中使用它，就像这段代码

[Intercept(typeof(LoggerInterceptor))] //logger
public class SomeService : ISomeService
{
    private readonly ISomeRepository someRepository;

    public SomeService(SomeRepository someRepository)
    {
        this.someRepository = someRepository;
    }

    public IEnumerable<SomeDto> GetAll()
    {
        // code
    }

    public SomeDto GetById()
    {
        // code
    }

    [Transactional]
    public int Create(SomeDto someDto)
    {
        // code to insert
    }
}

Answer 1

Intercept方法的invocation参数中包含一个Method属性是当前拦截方法的一个MethodInfo。

您可以使用此属性来做您想做的事。

例如使用方法名：

public void Intercept(IInvocation invocation)
{
    if (invocation.MethodInvocationTarget.Name != nameof(ISomeService.Create))
    {
        invocation.Proceed();
        return;
    }
    using (var transaction = ...)
    {
        try
        {
            invocation.Proceed();
            transaction.Commit();
        }
        catch
        {
            transaction.Rollback();
        }
        finally
        {
            transaction.Dispose();
        }
    }
}

或基于目标方法的属性：

if (!invocation.MethodInvocationTarget
               .CustomAttributes
               .Any(a => a.AttributeType == typeof(TransactionalAttribute)))

您也可以使用 IInterceptorSelector 类型，但需要更多工作才能将其注册到 Autofac

Answer 2

我用 ProxyGenerationHook 解决了这个问题。请参阅

创建您的自定义属性以选择要拦截的方法。该属性的目标应该是 Method.

    [System.AttributeUsage(AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
    sealed class UseInterceptorAttribute : Attribute
    {
        public UseInterceptorAttribute()
        {
        }
    }

创建您的服务接口和服务class:

    public interface ISomeService
    {
        void GetWithoutInterceptor();

        [UseInterceptor]
        void GetWithInterceptor();
    }

    public class SomeService
    {
        void GetWithoutInterceptor()
        {
            //This method will not be intercepted...
        }

        [UseInterceptor]
        void GetWithInterceptor()
        {
            //This method will be intercepted...
        }
    }

创建您的ProxyGenerationHook

    public class SomeServiceProxyGenerationHook : IProxyGenerationHook
    {
        public void MethodsInspected()
        {
        }

        public void NonProxyableMemberNotification(Type type, MemberInfo memberInfo)
        {
        }

        public bool ShouldInterceptMethod(Type type, MethodInfo methodInfo)
        {
            return methodInfo
                .CustomAttributes
                .Any(a => a.AttributeType == typeof(UseInterceptorAttribute));
        }
    }

不要使用属性来启用拦截器。启用它时像这样注册您的服务：

    public class AutofacDependencyResolver
    {
        private readonly IContainer _container;
        public AutofacDependencyResolver()
        {
            _container = BuildContainer();
        }

        private IContainer BuildContainer()
        {
            var proxyGenerationOptions = new ProxyGenerationOptions(new ProductServiceProxyGenerationHook());

            builder.RegisterType<SomeService>()
                .As<ISomeService>()
                .EnableInterfaceInterceptors(proxyGenerationOptions)
                .InterceptedBy(typeof(TransactionalInterceptor))

            builder.Register(c => new TransactionalInterceptor());
            return builder.Build();
        }

        public T GetService<T>()
            where T:class
        {
            var result = _container.TryResolve(out T serviceInstance);
            return serviceInstance ?? throw new Exception($"The service could not found: {nameof(T)}");
        }
    }

此解决方案遵循此 article

我还上传了关于此解决方案的最小 example。

Answer 3

也可以试试，很简单https://fs7744.github.io/Norns.Urd/index.html

public class AddTenInterceptorAttribute : AbstractInterceptorAttribute
{
    public override void Invoke(AspectContext context, AspectDelegate next)
    {
        next(context);
        AddTen(context);
    }

    private static void AddTen(AspectContext context)
    {
        if (context.ReturnValue is int i)
        {
            context.ReturnValue = i + 10;
        }
        else if(context.ReturnValue is double d)
        {
            context.ReturnValue = d + 10.0;
        }
    }

    public override async Task InvokeAsync(AspectContext context, AsyncAspectDelegate next)
    {
        await next(context);
        AddTen(context);
    }
}


[AddTenInterceptor]
public interface IGenericTest<T, R> : IDisposable
{
    // or
    //[AddTenInterceptor]
    T GetT();
}

.NET Core 2 中使用 Castle DynamicProxy 的 Autofac 方法级拦截

Autofac method level interception with Castle DynamicProxy in .NET Core 2

c#

castle-dynamicproxy

autofac