I'm migrating from Unity to StructureMap. I've made some use of Unity's InterceptionBehavior.
I thought I could switch that to use StructureMap .InterceptWith and the DynamicProxyInterceptor but my interceptors have dependencies and I can't work out how to compose the interceptors using StructureMap.
var container = new Container(x =>
{
x.For<IMathService>().Use<MathService>()
.InterceptWith(new DynamicProxyInterceptor<IMathService>(new IInterceptionBehavior[]
{
// I WANT TO COMPOSE THESE INTERCEPTORS
new NegatingInterceptor(),
new CachingInterceptor()
}));
});
At the moment the only thing I can think that might be a solution is to expose my IContainer from the static IoC class and resolve my dependencies manually in my interceptor.
Eventually I'll probably get around to replacing my dynamic proxies with decorators but I'm not quite at that stage yet. I just want to get it up and running again as soon as possible so I can prove the other changes are all successful before I start to make additional changes.
Okay, I'm an idiot, you just pass an array of types instead of instances to the DynamicProxyInterceptor constructor
var container = new Container(x =>
{
x.For<IMathService>().Use<MathService>()
.InterceptWith(new DynamicProxyInterceptor<IMathService>(
new Type[]
{
// I WANT TO COMPOSE THESE INTERCEPTORS
typeof(NegatingInterceptor),
typeof(CachingInterceptor)
}));
});
Related
I've used Autofac for years and never seen this behavior: after building, the app runs fine. However, after the app pool is recycled (I tested this by touching the web.config), I get a DependencyResolutionException:
None of the constructors found with 'Autofac.Core.Activators.Reflection.DefaultConstructorFinder' on type 'Namespace.Controllers.HomeController' can be invoked with the available services and parameters
HomeController has one dependency, which has other dependencies, etc. But I know it can resolve them, because it does before it's recycled. Why on earth would this happen???
I autowire everything like so:
public static IContainer GetAutoFacContainer()
{
var builder = new ContainerBuilder();
var assembliesToRegister = AppDomain.CurrentDomain.GetAssemblies()
.Where(a => a.FullName.StartsWith("Prefix")).ToArray();
builder.RegisterAssemblyTypes(assembliesToRegister)
.AsImplementedInterfaces().AsSelf().PropertiesAutowired().InstancePerLifetimeScope();
return builder.Build();
}
Then I use the container for WebAPI and MVC Controllers.
var autoFacContainer = DependencyRegistrar.GetAutoFacContainer();
DependencyResolver.SetResolver(new AutofacDependencyResolver(autoFacContainer));
GlobalConfiguration.Configuration.DependencyResolver =
new AutofacWebApiDependencyResolver(autoFacContainer);
Thanks to Steven's comment above, I did find the answer on the other question as well as the Autofac site. Why these never turned up in my research I don't know.
http://docs.autofac.org/en/latest/faq/iis-restart.html
The Solution
Change AppDomain.CurrentDomain.GetAssemblies()
To BuildManager.GetReferencedAssemblies().Cast<Assembly>()
Done!
I'm attempting to implement Dependency Injection into my architecture (MVC, DDD - Domain Model, Repository). And my architecture includes ASP.NET Identity 2.0.
At this stage, I don't want DI controlling any of the Identity 2.0 objects (UserAdminController, RolesAdminController...). I'd prefer the security objects outside of DI. At this stage, integrating the Identity objects in DI looks very difficult. I had a good look to see if someone has already done this, so I could read and learn how to do this. I couldn't find anything. (Found one post which came close, but no resolution).
Anyway, I've followed the Simple Injector MVC implementation (see standard code below), and trying many things, I believe the problem lies in me calling RegisterMvcControllers.
Correct me if I'm wrong, but this statement will pickup all controllers with their name post-fixed with "controller".
Question: How can I select which controllers get registered with Simple Injector? (Is this called manually registering?)
Any help would be greatly appreciated, as I've spent most of today trying to get my head around all this, and proceed to the next step, i.e. have DI implemented, and instantiating my objects.
...
...
... called from Application_Start()
// Create a Simple Injector container
var container = new Container();
// Configure the container
InitializeContainer(container);
container.RegisterMvcControllers(Assembly.GetExecutingAssembly());
// Verify the container's configuration
container.Verify();
DependencyResolver.SetResolver(new SimpleInjectorDependencyResolver(container));
private static void InitializeContainer(Container container)
{
container.Register<MyService1>();
container.Register<IMyRepositoryA, MyRepositoryA>();
// Trying to include Identity into Simple Injector - please ignore
container.Register<IUserStore<ApplicationUser>>(() => new UserStore<ApplicationUser>(new ApplicationDbContext()));
}
The RegisterMvcControllers has the following constraints on the types it registers:
The type must be public
The type must implement System.Web.Mvc.IController
The type must not be abstract
The type must not be a generic type definition
Its name must end with "Controller"
You can see what happens here in the source code.
The RegisterMvcControllers extension method calls into the SimpleInjectorMvcExtensions.GetControllerTypesToRegister method to get the list of controllers to register. You can call that method yourself to see what is registered as follows:
var registeredControllerTypes =
SimpleInjectorMvcExtensions.GetControllerTypesToRegister(
container, Assembly.GetExecutingAssembly())
So instead of calling RegisterMvcControllers you can register the controllers yourself by calling the GetControllerTypesToRegister method:
var registeredControllerTypes =
SimpleInjectorMvcExtensions.GetControllerTypesToRegister(
container, Assembly.GetExecutingAssembly());
foreach (var controllerType in registeredControllerTypes)
{
container.Register(controllerType, controllerType, Lifestyle.Transient);
}
This way you can filter out any controller you want to register manually:
var registeredControllerTypes =
SimpleInjectorMvcExtensions.GetControllerTypesToRegister(
container, Assembly.GetExecutingAssembly())
.Where(type => type.Name != "UserStore`1");
foreach (var controllerType in registeredControllerTypes)
{
container.Register(controllerType, controllerType, Lifestyle.Transient);
}
Another option is to override the registration:
container.RegisterMvcControllers(Assembly.GetExecutingAssembly());
container.Options.AllowOverridingRegistrations = true;
container.Register<IUserStore<ApplicationUser>>(
() => new UserStore<ApplicationUser>(new ApplicationDbContext()))
// Always set the option back to false ASAP to prevent configuration errors.
container.Options.AllowOverridingRegistrations = false;
We're trying to use MEF 2 with ASP.NET MVC 4 to support an extensible application. There are really 2 parts to this question (hope that's okay SO gods):
How do we use Microsoft.Composition and the MVC container code (MEF/MVC demo source) to replace Ninject as our DI for ICoreService, ICoreRepository, IUnitOfWork, and IDbContext?
It looks like we can't use both Ninject and the MVC container at the same time (I'm sure many are saying "duh"), so we'd like to go with MEF, if possible. I tried removing Ninject and setting [Export] attributes on each of the relevant implementations, spanning two assemblies in addition to the web project, but Save() failed to persist with no errors. I interpreted that as a singleton issue, but could not figure out how to sort it out (incl. [Shared]).
How do we load multiple assemblies dynamically at runtime?
I understand how to use CompositionContainer.AddAssemblies() to load specific DLLs, but for our application to be properly extensible, we require something more akin to how I (vaguely) understand catalogs in "full" MEF, which have been stripped out from the Microsoft.Composition package (I think?); to allow us to load all IPluggable (or whatever) assemblies, which will include their own UI, service, and repository layers and tie in to the Core service/repo too.
EDIT 1
A little more reading solved the first problem which was, indeed, a singleton issue. Attaching [Shared(Boundaries.HttpRequest)] to the CoreDbContext solved the persistence problem. When I tried simply [Shared], it expanded the 'singletonization' to the Application level (cross-request) and threw an exception saying that the edited object was already in the EF cache.
EDIT 2
I used the iterative assembly loading "meat" from Nick Blumhardt's answer below to update my Global.asax.cs code. The standard MEF 2 container from his code did not work in mine, probably because I'm using the MEF 2(?) MVC container. Summary: the code listed below now works as desired.
CoreDbContext.cs (Data.csproj)
[Export(typeof(IDbContext))]
[Shared(Boundaries.HttpRequest)]
public class CoreDbContext : IDbContext { ... }
CoreRepository.cs (Data.csproj)
[Export(typeof(IUnitOfWork))]
[Export(typeof(ICoreRepository))]
public class CoreRepository : ICoreRepository, IUnitOfWork
{
[ImportingConstructor]
public CoreRepository(IInsightDbContext context)
{
_context = context;
}
...
}
CoreService.cs (Services.csproj)
[Export(typeof(ICoreService))]
public class CoreService : ICoreService
{
[ImportingConstructor]
public CoreService(ICoreRepository repository, IUnitOfWork unitOfWork)
{
_repository = repository;
_unitOfWork = unitOfWork;
}
...
}
UserController.cs (Web.csproj)
public class UsersController : Controller
{
[ImportingConstructor]
public UsersController(ICoreService service)
{
_service = service;
}
...
}
Global.asax.cs (Web.csproj)
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
CompositionProvider.AddAssemblies(
typeof(ICoreRepository).Assembly,
typeof(ICoreService).Assembly,
);
// EDIT 2 --
// updated code to answer my 2nd question based on Nick Blumhardt's answer
foreach (var file in System.IO.Directory.GetFiles(Server.MapPath("Plugins"), "*.dll"))
{
try
{
var name = System.Reflection.AssemblyName.GetAssemblyName(file);
var assembly = System.Reflection.Assembly.Load(name);
CompositionProvider.AddAssembly(assembly);
}
catch
{
// You'll need to craft exception handling to
// your specific scenario.
}
}
}
}
If I understand you correctly, you're looking for code that will load all assemblies from a directory and load them into the container; here's a skeleton for doing that:
var config = new ContainerConfiguration();
foreach (var file in Directory.GetFiles(#".\Plugins", "*.dll"))
{
try
{
var name = AssemblyName.GetAssemblyName(file);
var assembly = Assembly.Load(name);
config.WithAssembly(assembly);
}
catch
{
// You'll need to craft exception handling to
// your specific scenario.
}
}
var container = config.CreateContainer();
// ...
Hammett discusses this scenario and shows a more complete version in F# here: http://hammett.castleproject.org/index.php/2011/12/a-decent-directorycatalog-implementation/
Note, this won't detect assemblies added to the directory after the application launches - Microsoft.Composition isn't intended for that kind of use, so if the set of plug-ins changes your best bet is to detect that with a directory watcher and prompt the user to restart the app. HTH!
MEF is not intended to be used as DI framework. Which means that you should separate your "plugins" (whatever they are) composition from your infrastructure dependencies, and implement the former via MEF and the latter via whatever DI framework you prefer.
I think there are a little misunderstandings on what MEF can and can't do.
Originally MEF was conceived as purely an extensibility architecture, but as the framework evolved up to its first release, it can be fully supported as a DI container also. MEF will handle dependency injection for you, and does so through it's ExportProvider architecture. It is also entirely possible to use other DI frameworks with MEF. So in reality there are a number of ways things could be achieved:
Build a NinjectExportProvider that you can plug into MEF, so when MEF is searching for available exports, it will be able to interrogate your Ninject container.
Use an implementation of the Common Services Locator pattern to bridge between MEF and Ninject or vice versa.
Because you are using MEF for the extensibility, you'll probably want to use the former, as this exposes your Ninject components to MEF, which in turn exposes them to your plugins.
The other thing to consider, which is a bit disappointing, is in reality there isn't a lot of room for automagically plugging in of features ala Wordpress on ASP.NET. ASP.NET is a compiled and managed environment, and because of that you either resort to late-binding by loading assemblies manually at runtime, or you restart the application to pick up the new plugins, which sort of defeats the object of being able to plug new extensions in through the application.
My advice, is plan your architecture to pick up any extensibility points as startup and assume that any core changes will require a deployment and application restart.
In terms of the direct questions asked:
The CompositionProvider accepts in instance of ContainerConfiguration which is used internally to create the CompositionContainer used by the provider. So you could use this as the point by which you customise how you want your container to be instantiated. The ContainerConfiguration supports a WithProvider method:
var configuration = new ContainerConfiguration().WithProvider(new NinjectExportDescriptorProvider(kernel));
CompositionProvider.SetConfiguration(configuration);
Where NinjectExportDescriptorProvider might be:
public class NinjectExportDescriptorProvider: ExportDescriptorProvider
{
private readonly IKernel _kernel;
public NinjectExportDescriptorProvider(IKernel kernel)
{
if (kernel == null) throw new ArgumentNullException("kernel");
_kernel = kernel;
}
public override IEnumerable<ExportDescriptorPromise> GetExportDescriptors(
CompositionContract contract, DependencyAccessor dependencyAccessor)
{
var type = contract.ContractType;
if (!_kernel.GetBindings(type).Any())
return NoExportDescriptors;
return new[] {
new ExportDescriptorPromise(
contract,
"Ninject Kernel",
true, // Hmmm... need to consider this, setting it to true will create it as a shared part, false as new instance each time,
NoDependencies,
_ => ExportDescriptor.Create((c, o) => _kernel.Get(type), NoMetadata)) };
}
}
}
Note: I have not tested this, this is all theory, and is based on the example AppSettingsExportDescriptorProvider at: http://mef.codeplex.com/wikipage?title=ProgrammingModelExtensions
It's different from using the standard ExportProvider, because using the CompostionProvider is built around lightweight composition. But essentially you're wrapping up access to your Ninject kernel and making it available to your CompositionContainer.
As with adding a specific new provider (see above), you can use the ContainerConfiguration to read the available assemblies, probably something like:
var configuration = new ContainerConfiguration().WithAssemblies(AppDomain.GetAssemblies())
Again, I haven't tested all of this, but I hope it at least points you in the right direction.
An approach we've taken recently is to include a StructureMap registry in each of our assemblies that set's up the default dependencies.
We use a scanner to do this:
cfg.Scan(scanner =>
{
scanner.TheCallingAssembly();
scanner.Assembly("Assembly1");
scanner.Assembly("Assembly2");
scanner.Assembly("Assembly3");
scanner.LookForRegistries();
});
The idea is that we can then override the default dependencies from the main application.
The question is, where should we register these overrides? i.e. before we scan?, after we scan?
Furthermore, does the order of the assemblies specified in the scan expression, effect the order in which the dependencies are registered. So in the example above, would registries contained in the main application (TheCallingAssembly) get overrided by those in "Assembly3"?
Many thanks
Ben
Registries in TheCallingAssembly will be overridden by those you register in Assembly1, 2 etc.
So if you register ISomeInterface in everyone of those assemblies, the one in Assembly3 will be the default. The ones registered in the others assemblies you can get from structuremap by calling
container.GetAllInstances<ISomeInterface>();
This will return a IList of all the registered ISomeInterface in structuremap.
If you want to override the ones you get by scanning you have to configure the container again for some reason. If you don't do that, the last scanned type is the default.
In this example the ISomeInterface registered in Assembly1 is the default. When you look at the code, one would belive that SomeOtherClass is the default. But it is actually the one registered in Assembly1 that is the default.
var container = new Container(x => {
x.Scan(scanner =>
{
scanner.TheCallingAssembly();
scanner.Assembly("Assembly1");
scanner.LookForRegistries();
});
x.For<ISomeInterface>().Use<SomeOtherClass>();
});
So to override the mappings from the scanned assemblies. You have to configure the container again like this example. Here SomeOtherClass is the default for ISomeInterface.
var container = new Container(x => {
x.Scan(scanner =>
{
scanner.TheCallingAssembly();
scanner.Assembly("Assembly1");
scanner.LookForRegistries();
});
});
container.Configure(x => x.For<ISomeInterface>().Use<SomeOtherClass>());
Hi there Im using windsor as a DI container,
my code is below
public static class ContainerBuilder
{
public static IWindsorContainer Build()
{
var container = new WindsorContainer("Configuration\\Windsor.config");
// automatically register controllers
container.Register(AllTypes
.Of<Controller>()
.FromAssembly(Assembly.GetExecutingAssembly())
.Configure(c => c.LifeStyle.Transient.Named(c.Implementation.Name.ToLower())));
container.Register(
Component.For<IServiceLocator>().Instance(new WindsorServiceLocator(container)),
Component.For(typeof(IRepository<>)).ImplementedBy(typeof(NHibernateRepository<>)).LifeStyle.Transient
);
return container;
}
}
I need to call this from a test project , the problem is that when I do this the windsor.config is never found and the test seems to always fail, where is the best way to place this config file or is there a better approach to doing this?
Thanks
Just make the config path configurable, e.g.
public static IWindsorContainer Build(string configPath) {
var container = new WindsorContainer(configPath);
...
}
In your app the configPath is "Configuration\Windsor.config" while in your tests you'll have a path like "....\Configuration\Windsor.config".
Note that you shouldn't generally depend on the container in your tests, unless you're running some integration tests.
Also a static container builder doesn't seem like a good idea, take a look at Windsor Installers to register your components in a modular way.