We are using StructureMap as container in my current project and all has been working well until we had to inject dependencies to a custom attribute we are using.
First, code for registering stuff in the container would look like this...
Container = new Container();
Registry = new Registry();
ServiceLocator = new StructureMapServiceLocator(Container);
Registry.For<IServiceLocator>().Use(ServiceLocator);
Registry.For<IHitCounter>().Add<HitCounter>();
Registry.For<IHitCountAttribute>().Use<HitCountAttribute>();
Registry.SetAllProperties(policy => policy.OfType<IHitCounter>());
Container.Configure(config => config.AddRegistry(Registry));
The kind of registering above do work for a normal class with setter injection (and constructor injection) but obviously not for an attribute class.
An attribute class could look like this...
public class HitCountAttribute : ActionFilterAttribute, IHitCountAttribute
{
public IHitCounter HitCounter { get; set; }
public override void OnResultExecuted(ResultExecutedContext filterContext)
{
HitCounter.Count(HttpContext.Current.Request.Url.ToString());
base.OnResultExecuted(filterContext);
}
}
The interface look like this...
public interface IHitCountAttribute
{
IHitCounter HitCounter { get; set; }
void OnResultExecuted(ResultExecutedContext filterContext);
}
Is it even possible to inject dependencies to an attribute? As it is instantiated by the runtime...
Is there any other way to solve the problem with the dependencies?
Related
In broader terms what I am trying to achieve with Autofac is to pass the dependant (a.k.a. parent) object to its dependencies.
For example:
interface IDependency {}
class Dependant
{
IDependency Dependency { get; set; }
}
class ConcreteDependency : IDependency
{
ConcreteDependency(Dependant dependant) { /* ... */ }
}
I am hoping this could work, because Dependant breaks the dependency loop using property injection (meaning you can create an instance of Dependant, before having to resolve IDependency). Whilst, if both classes used ctor-injection this wouldn't be possible.
Specifically, I am trying to inject the current ASP.NET MVC controller instance to one of its dependencies.
Take a look at:
public abstract class ApplicationController : Controller
{
public ILogger Logger { get; set;}
}
public class SomeController : ApplicationController
{
[HttpPost]
public ActionResult Create(FormCollection formData)
{
// something fails...
this.Logger.Log("Something has failed.");
}
}
public interface ILogger
{
public void Log(string message);
}
public class TempDataLogger : ILogger
{
private ControllerBase controller;
public NullLogger(ControllerBase controller)
{
this.controller = controller;
}
public void Log(string message)
{
this.controller.TempData["Log"] = message;
}
}
In plain English the above code uses TempData as a way of "logging" messages (maybe to print it out in a nice way in view-layout or something...).
Simple enough all controllers are registered in Autofac:
builder.RegisterControllers(typeof(MvcApplication).Assembly)
.PropertiesAutowired(); // not strictly necessary
But then, how can I tweak the ILogger registration below to make it work?
builder.RegisterType<TempDataLogger>()
.As<ILogger>()
.InstancePerRequest();
Is this even possible in Autofac?
Thank you.
In case anyone else is interested, the solution below is the closest I was able to get so far:
builder.RegisterControllers(typeof(MvcApplication).Assembly)
.PropertiesAutowired() // not strictly necessary
.OnActivating(e => ((ApplicationController)e.Instance).Logger = new TempDataLogger((ApplicationController)e.Instance));
... and therefore, no need to;
builder.RegisterType<TempDataLogger>()
.As<ILogger>()
.InstancePerRequest();
I'm trying to use SimpleInjector 2.7.3 (IoC container) within an Asp.Net MVC + Web API application.
I've had a couple of problems trying to set it up for both MVC and Web API on the same project until I found this link:
http://methoddev.com/blg/let-s-talk-software/310/simple-injector-in-asp-net-mvc-webapi
After following the link's example, here's what I got:
One of my Web API controllers:
public class UserController : BaseApiController
{
private readonly IUserService service;
public UserController(IUserService userService)
{
// I should point that IUserService is being injected correctly here
this.service = userService;
}
public IHttpActionResult Post(CreateUserRequest request)
{
return Ok();
}
}
The problem happens when I try to execute the Post operation. The CreateUserRequest class itself has a dependency.
public class CreateUserRequest : IValidatableObject
{
private readonly IValidator<CreateUserRequest> validator;
public CreateUserRequest(IValidator<CreateUserRequest> _validator)
{
// _validator is not being injected, I'm getting null here
validator = _validator;
}
public string SomeProperty { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
// My validation logic here must call the validator injected
// when the object was created.
return null;
}
}
I should point that IValidator is an interface from the FluentValidator package.
Anyway, when CreateUserRequest is instantiated the validator is null, which means it's not being injected.
When I'm creating the SimpleInjector Container I can see the type correctly registered, so I don't think that is a problem.
I did the following change to CreateUserRequest class:
public class CreateUserRequest : IValidatableObject
{
private readonly CreateUserRequestValidator validator;
// Changed here to the concrete class
public CreateUserRequest(CreateUserRequestValidator _validator)
{
validator = _validator;
}
// ...
}
So, I changed the interface to a concrete class and I'm still receiving a null there.
The only thing I can imagine is that this is somehow related to the custom dependency resolver suggested by the aforementioned link. I needed to use that in order to have the same dependency resolution logic for both MVC and Web API. Here's the code:
public class SimpleInjectorDependencyResolver : System.Web.Mvc.IDependencyResolver,
System.Web.Http.Dependencies.IDependencyResolver,
System.Web.Http.Dependencies.IDependencyScope
{
public SimpleInjectorDependencyResolver(Container container)
{
if (container == null)
{
throw new ArgumentNullException("container");
}
this.Container = container;
}
public Container Container { get; private set; }
public object GetService(Type serviceType)
{
if (!serviceType.IsAbstract && typeof(IController).IsAssignableFrom(serviceType))
{
return this.Container.GetInstance(serviceType);
}
return ((IServiceProvider)this.Container).GetService(serviceType);
}
public IEnumerable<object> GetServices(Type serviceType)
{
return this.Container.GetAllInstances(serviceType);
}
IDependencyScope System.Web.Http.Dependencies.IDependencyResolver.BeginScope()
{
return this;
}
object IDependencyScope.GetService(Type serviceType)
{
return ((IServiceProvider)this.Container).GetService(serviceType);
}
IEnumerable<object> IDependencyScope.GetServices(Type serviceType)
{
return this.Container.GetAllInstances(serviceType);
}
void IDisposable.Dispose()
{
}
}
I don't really know a lot of the plumbing behind MVC and Web API (specially the custom dependency resolver feature), so, I'm really stuck on this one.
I appreciate any help figuring that out. Thanks.
--UPDATE--
In addition to the answer given by Steven, I would like to leave a link to whoever falls into the same problem. It's a great resource:
https://brettedotnet.wordpress.com/2014/07/16/web-api-and-interface-parameters/
The reason why your view model object isn't auto-wired by Simple Injector is because both MVC and Web API don't build view model objects using the IDependencyResolver. So creating a special dependency resolver won't work. If you want to let your view models to be auto-wired, you will have to override the default model binder in MVC and Web API.
But I urge you not to do this. In my opinion, a model binder should just do data conversion and a view model should be a plain DTO. Although it is fine to mark view models with validation attributes, letting them have behavior using services that might even trigger any database communication is a big no-no in my book. This can complicate development tremendously.
This however means that this validator should be injected elsewhere. Without making any changes to your architecture, this basically means you will have to inject that validator in the controller instead:
public class UserController : BaseApiController
{
private readonly IUserService service;
private readonly IValidator<CreateUserRequest> validator;
public UserController(IUserService userService,
IValidator<CreateUserRequest> validator)
{
this.service = userService;
this.validator = validator;
}
}
Obviously this can easily complicate your controllers with extra dependencies and logic, but that's because validation is a cross-cutting concern that you would like to probably keep out of your controllers.
If you try to address this, you will eventually end up with a message passing architecture such as described here.
I'm trying to resolve the dependencies of my custom AuthorizeAttribute which I use to decorate my API controllers in an MVC4 app. Problem is that I keep getting a NullReferenceException on the service dependency I use within my custom filter. Here is my Autofac configuration:
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
var builder = new ContainerBuilder();
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().InstancePerApiRequest();
builder.RegisterType<DatabaseFactory>().As<IDatabaseFactory>().InstancePerApiRequest();
builder.RegisterAssemblyTypes(typeof(UserProfileRepository).Assembly)
.Where(t => t.Name.EndsWith("Repository"))
.AsImplementedInterfaces().InstancePerApiRequest();
builder.RegisterAssemblyTypes(typeof(IUserProfileMapper).Assembly)
.Where(t => t.Name.EndsWith("Mapper"))
.AsImplementedInterfaces().InstancePerApiRequest();
builder.RegisterAssemblyTypes(typeof(UserProfileSvc).Assembly)
.Where(t => t.Name.EndsWith("Svc"))
.AsImplementedInterfaces().InstancePerApiRequest();
builder.RegisterWebApiFilterProvider(config);
var container = builder.Build();
var resolver = new AutofacWebApiDependencyResolver(container);
config.DependencyResolver = resolver;
}
}
and my custom authorize filter:
public class MyAuthorizeAttribute : AuthorizeAttribute
{
public IAuthenticationSvc _authenticationSvc;
protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext)
{
if (!base.IsAuthorized(actionContext))
{
return false;
}
var trueUserId = WebSecurity.CurrentUserId;
if (_authenticationSvc.GetUsersRoles(trueUserId).Any(x => x == "Admin")) return true;
// NullReferenceException on _authenticationSvc
}
}
According to the official docs all that is needed is:
var builder = new ContainerBuilder();
builder.RegisterWebApiFilterProvider(GlobalConfiguration.Configuration);
But that doesn't seem to do the trick either. Appreciate any help.
I think Autofac's documentation offers much simpler solution for WebApi action filters.
public interface ServiceCallActionFilterAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
// Get the request lifetime scope so you can resolve services.
var requestScope = actionContext.Request.GetDependencyScope();
// Resolve the service you want to use.
var service = requestScope.GetService(typeof(IMyService)) as IMyService;
// Do the rest of the work in the filter.
service.DoWork();
}
}
It is not "pure DI" as it is using service locator, but it is simple and works with the request scope. You don't need to worry about registering specific action filter for each WebApi controller.
Source:
http://autofac.readthedocs.io/en/latest/integration/webapi.html#provide-filters-via-dependency-injection
You should configure property injection for your attribute
public class MyAuthorizeAttribute : AuthorizeAttribute
{
public IAuthenticationSvc AuthenticationSvc { get; set; }
}
and the builder
builder.RegisterType<MyAuthorizeAttribute>().PropertiesAutowired();
In addition to #Toan Nguyen's answer, if you have this...
public class MyAuthorizeAttribute : AuthorizeAttribute
{
public IAuthenticationSvc AuthenticationSvc { get; set; }
}
... it seems you also need (or may need) the first line below:
builder.RegisterFilterProvider();
builder.RegisterType<MyAuthorizeAttribute>().PropertiesAutowired();
Reference: http://itprojectpool.blogspot.com.au/2014/03/autofac-di-on-action-filters.html
In addition to configuring property injection, as outlined in other answers, you can also explicitly resolve dependencies in the OnActivating callback.
public class MyAuthorizeAttribute : AuthorizeAttribute
{
private IAuthenticationSvc _authenticationSvc;
public void SetAuthenticationSvc(IAuthenticationSvc svc)
{
this._authenticationSvc = svc;
}
}
And then register the type:
builder.RegisterType<MyAuthorizeAttribute>()
.OnActivating(_ => _.Instance.SetAuthenticationSvc(_.Context.Resolve<IAuthenticationSvc>()));
Note: You can do the same with a property instead of a method. I chose to use a method here only to illustrate that this solution was not dependent on PropertiesAutowired.
I would like to have my own injection attribute so that I am not coupling my code to a particular IOC framework. I have a custom injection attribute that my code uses to denote that a property should be injected.
public class CustomInjectAttribute : Attribute {}
Fictitious example below...
public class Robot : IRobot
{
[CustomInject]
public ILaser Zap { get; set; }
...
}
In Ninject, you can setup an injection Heuristic to find that attribute, and inject like;
public class NinjectInjectionHeuristic : NinjectComponent, IInjectionHeuristic, INinjectComponent, IDisposable
{
public new bool ShouldInject(MemberInfo member)
{
return member.IsDefined(typeof(CustomInjectAttribute), true);
}
}
and then register the heuristic with the kernel.
Kernel.Components.Get<ISelector>().InjectionHeuristics.Add(new NinjectInjectionHeuristic());
How would I go about achieving this with StructureMap. I know StructureMap has its own SetterProperties and attributes, but I'm looking for a way to decouple from that as you can with Ninject in the above example.
Use the SetAllProperties() method in your ObjectFactory or Container configuration. For example:
new Container(x =>
{
x.SetAllProperties(by =>
{
by.Matching(prop => prop.HasAttribute<CustomInjectAttribute>());
});
});
This makes use of a handy extension method (that should be in the BCL):
public static bool HasAttribute<T>(this ICustomAttributeProvider provider) where T : Attribute
{
return provider.GetCustomAttributes(typeof (T), true).Any();
}
I'm a newbie when it comes to DI and ninject and I'm struggling a bit
about when the actual injection should happen and how to start the
binding.
I'm using it already in my web application and it working fine there,
but now I want to use injection in a class library.
Say I have a class like this:
public class TestClass
{
[Inject]
public IRoleRepository RoleRepository { get; set; }
[Inject]
public ISiteRepository SiteRepository { get; set; }
[Inject]
public IUserRepository UserRepository { get; set; }
private readonly string _fileName;
public TestClass(string fileName)
{
_fileName = fileName;
}
public void ImportData()
{
var user = UserRepository.GetByUserName("myname");
var role = RoleRepository.GetByRoleName("myname");
var site = SiteRepository.GetByID(15);
// Use file etc
}
}
I want to use property injection here because I need to pass in a
filename in my constructor. Am I correct in saying that if I need to
pass in a constructor parameter, I cannot use constructor injection?
If I can use constructor injection with additional parameters, how do
I pass those parameters in?
I have a console app that consumes by Test class that looks as
follows:
class Program
{
static void Main(string[] args)
{
// NinjectRepositoryModule Binds my IRoleRepository etc to concrete
// types and works fine as I'm using it in my web app without any
// problems
IKernel kernel = new StandardKernel(new NinjectRepositoryModule());
var test = new TestClass("filename");
test.ImportData();
}
}
My problem is that when I call test.ImportData() my repositories are null - nothing has been injected into them. I have tried creating another module and calling
Bind<TestClass>().ToSelf();
as I thought this might resolve all injection properties in TestClass but I'm getting nowhere.
I'm sure this is a trivial problem, but I just can't seem to find out
how to go about this.
You are directly newing TestClass, which Ninject has no way of intercepting - remember there's no magic like code transformation intercepting your news etc.
You should be doing kernel.Get<TestClass> instead.
Failing that, you can inject it after you new it with a kernel.Inject( test);
I think there's an article in the wiki that talks about Inject vs Get etc.
Note that in general, direct Get or Inject calls are a Doing It Wrong smell of Service Location, which is an antipattern. In the case of your web app, the NinjectHttpModule and PageBase are the hook that intercepts object creation - there are similar interceptors / logical places to intercept in other styles of app.
Re your Bind<TestClass>().ToSelf(), generally a StandardKernel has ImplicitSelfBinding = true which would make that unnecessary (unless you want to influence its Scope to be something other than .InTransientScope()).
A final style point:- you're using property injection. There are rarely good reasons for this, so you should be using constructor injection instead.
And do go buy Dependency Injection in .NET by #Mark Seemann, who has stacks of excellent posts around here which cover lots of important but subtle considerations in and around the Dependency Injection area.
OK,
I've found out how to do what I need, thanks in part to your comments Ruben. I've created a new module that basically holds the configuration that I use in the class library. Within this module I can either Bind using a placeholder Interface or I can add a constructor parameter to the CustomerLoader.
Below is the code from a dummy console app to demonstrating both ways.
This might help someone else getting started with Ninject!
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Ninject.Core;
using Ninject.Core.Behavior;
namespace NinjectTest
{
public class Program
{
public static void Main(string[] args)
{
var kernel = new StandardKernel(new RepositoryModule(), new ProgramModule());
var loader = kernel.Get<CustomerLoader>();
loader.LoadCustomer();
Console.ReadKey();
}
}
public class ProgramModule : StandardModule
{
public override void Load()
{
// To get ninject to add the constructor parameter uncomment the line below
//Bind<CustomerLoader>().ToSelf().WithArgument("fileName", "string argument file name");
Bind<LiveFileName>().To<LiveFileName>();
}
}
public class RepositoryModule : StandardModule
{
public override void Load()
{
Bind<ICustomerRepository>().To<CustomerRepository>().Using<SingletonBehavior>();
}
}
public interface IFileNameContainer
{
string FileName { get; }
}
public class LiveFileName : IFileNameContainer
{
public string FileName
{
get { return "live file name"; }
}
}
public class CustomerLoader
{
[Inject]
public ICustomerRepository CustomerRepository { get; set; }
private string _fileName;
// To get ninject to add the constructor parameter uncomment the line below
//public CustomerLoader(string fileName)
//{
// _fileName = fileName;
//}
public CustomerLoader(IFileNameContainer fileNameContainer)
{
_fileName = fileNameContainer.FileName;
}
public void LoadCustomer()
{
Customer c = CustomerRepository.GetCustomer();
Console.WriteLine(string.Format("Name:{0}\nAge:{1}\nFile name is:{2}", c.Name, c.Age, _fileName));
}
}
public interface ICustomerRepository
{
Customer GetCustomer();
}
public class CustomerRepository : ICustomerRepository
{
public Customer GetCustomer()
{
return new Customer() { Name = "Ciaran", Age = 29 };
}
}
public class Customer
{
public string Name { get; set; }
public int Age { get; set; }
}
}