Using MediatR behaviors instead of Autofac decorators. Solves dotnet-architecture#187

Author: eiximenis

src/Services/Ordering/Ordering.API/Application/Behaviors/LoggingBehavior.cs

@@ -0,0 +1,23 @@
+using MediatR;
+using Microsoft.Extensions.Logging;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Ordering.API.Infrastructure.Behaviors
+{
+    public class LoggingBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
+    {
+        private readonly ILogger<LoggingBehavior<TRequest, TResponse>> _logger;
+        public LoggingBehavior(ILogger<LoggingBehavior<TRequest, TResponse>> logger) => _logger = logger;
+
+        public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next)
+        {
+            _logger.LogInformation($"Handling {typeof(TRequest).Name}");
+            var response = await next();
+            _logger.LogInformation($"Handled {typeof(TResponse).Name}");
+            return response;
+        }
+    }
+}

…ication/Decorators/ValidatorDecorator.cs …plication/Behaviors/ValidatorBehavior.cssrc/Services/Ordering/Ordering.API/Application/Decorators/ValidatorDecorator.cs renamed to src/Services/Ordering/Ordering.API/Application/Behaviors/ValidatorBehavior.cs src/Services/Ordering/Ordering.API/Application/Decorators/ValidatorDecorator.cs renamed to src/Services/Ordering/Ordering.API/Application/Behaviors/ValidatorBehavior.cs

@@ -1,33 +1,23 @@
 using FluentValidation;
 using MediatR;
+using Microsoft.Extensions.Logging;
 using Ordering.Domain.Exceptions;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 
-namespace Ordering.API.Application.Decorators
+namespace Ordering.API.Infrastructure.Behaviors
 {
-    public class ValidatorDecorator<TRequest, TResponse>
-        : IAsyncRequestHandler<TRequest, TResponse>
-         where TRequest : IRequest<TResponse>
+    public class ValidatorBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
     {
-        private readonly IAsyncRequestHandler<TRequest, TResponse> _inner;
         private readonly IValidator<TRequest>[] _validators;
+        public ValidatorBehavior(IValidator<TRequest>[] validators) => _validators = validators;
 
-
-        public ValidatorDecorator(
-            IAsyncRequestHandler<TRequest, TResponse> inner,
-            IValidator<TRequest>[] validators)
-        {
-            _inner = inner;
-            _validators = validators;
-        }
-
-        public async Task<TResponse> Handle(TRequest message)
+        public async Task<TResponse> Handle(TRequest request, RequestHandlerDelegate<TResponse> next)
         {
             var failures = _validators
-                .Select(v => v.Validate(message))
+                .Select(v => v.Validate(request))
                 .SelectMany(result => result.Errors)
                 .Where(error => error != null)
                 .ToList();
@@ -37,9 +27,8 @@ public async Task<TResponse> Handle(TRequest message)
                 throw new OrderingDomainException(
                     $"Command Validation Errors for type {typeof(TRequest).Name}", new ValidationException("Validation exception", failures));
             }
-            
-            var response = await _inner.Handle(message);
 
+            var response = await next();
             return response;
         }
     }

src/Services/Ordering/Ordering.API/Application/Decorators/LogDecorator.cs

@@ -3,11 +3,9 @@
 using FluentValidation;
 using MediatR;
 using Microsoft.eShopOnContainers.Services.Ordering.API.Application.Commands;
-using Microsoft.eShopOnContainers.Services.Ordering.API.Application.Decorators;
-using Ordering.API.Application.Decorators;
 using Ordering.API.Application.DomainEventHandlers.OrderStartedEvent;
 using Ordering.API.Application.Validations;
-using Ordering.Domain.Events;
+using Ordering.API.Infrastructure.Behaviors;
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
@@ -33,7 +31,7 @@ protected override void Load(ContainerBuilder builder)
                     .Where(i => i.IsClosedTypeOf(typeof(IAsyncNotificationHandler<>)))
                     .Select(i => new KeyedService("IAsyncNotificationHandler", i)))
                     .AsImplementedInterfaces();
-                    
+
 
             builder
                 .RegisterAssemblyTypes(typeof(CreateOrderCommandValidator).GetTypeInfo().Assembly)
@@ -45,25 +43,22 @@ protected override void Load(ContainerBuilder builder)
             {
                 var componentContext = context.Resolve<IComponentContext>();
                 return t => { object o; return componentContext.TryResolve(t, out o) ? o : null; };
-            });          
+            });
 
             builder.Register<MultiInstanceFactory>(context =>
             {
                 var componentContext = context.Resolve<IComponentContext>();
 
-                return t => (IEnumerable<object>)componentContext.Resolve(typeof(IEnumerable<>).MakeGenericType(t));
+                return t =>
+                {
+                    var resolved = (IEnumerable<object>)componentContext.Resolve(typeof(IEnumerable<>).MakeGenericType(t));
+                    return resolved;
+                };
             });
 
-            
-
-            builder.RegisterGenericDecorator(typeof(LogDecorator<,>),
-                    typeof(IAsyncRequestHandler<,>),
-                    "IAsyncRequestHandler")
-                    .Keyed("handlerDecorator", typeof(IAsyncRequestHandler<,>));
+            builder.RegisterGeneric(typeof(LoggingBehavior<,>)).As(typeof(IPipelineBehavior<,>));
+            builder.RegisterGeneric(typeof(ValidatorBehavior<,>)).As(typeof(IPipelineBehavior<,>));
 
-            builder.RegisterGenericDecorator(typeof(ValidatorDecorator<,>),
-                    typeof(IAsyncRequestHandler<,>),
-                    fromKey: "handlerDecorator");
         }
     }
 }