I have to validate incoming message before passing it to my consumer.
To do it, I need to request some data from the database.
Following the tutorials, I created extension method to apply my specification + filter to the consumer pipe. Something like this:
public static void UseArticlesImportValidation(this IConsumePipeConfigurator configurator){}
public class ArticlesImportValidationSpecification : IPipeSpecification<ConsumeContext<ArticlesImportNotification>>
and the Filter
public class ArticlesImportValidationFilter : IFilter<ConsumeContext<ArticlesImportNotification>>
Everything looks good, but I want to injection some business services in my Filter to reuse some functionality + DAL services. This works completely fine for my Consumer using Autofac extension method builder.RegisterConsumers(Assembly.GetExecutingAssembly());.
Should I use middleware for this at all? Any suggestions?
You need to have the built container in your specification (it is easy to pass as a parameter when you call AddPipeSpecification and then in the specification:
public void Apply(IPipeBuilder<T> builder)
{
builder.AddFilter(new ArticlesImportValidationFilter(container.Resolve<IDataAccessSomethingUseful>()));
}
But I would validate in the consumer or, if you want to keep them separate, have one consumer to validate and send the next message to do the actual job.
You should use Scoped Filters in this situation
Let's say you have a filter with dependency
public class MyConsumeFilter<T> :
IFilter<ConsumeContext<T>>
where T : class
{
public MyConsumeFilter(IMyDependency dependency) { }
public async Task Send(ConsumeContext<T> context, IPipe<ConsumeContext<T>> next) { }
public void Probe(ProbeContext context) { }
}
you should register this dependency in your DI container
services.AddScoped<IMyDependency, MyDependency>(); //register dependency
And now you are ready to add this filter to the consumer pipe by calling UseConsumeFilter method:
services.AddConsumer<MyConsumer>();
services.AddMassTransit(x =>
{
x.UsingRabbitMq((context, cfg) =>
{
cfg.ReceiveEndpoint("input-queue", e =>
{
e.UseConsumeFilter(typeof(MyConsumeFilter<>), context); //generic filter
e.ConfigureConsumer<MyConsumer>();
});
});
});
Related
I'm trying to write an ASP.NET Core 2.2 integration test, where the test setup decorates a specific service that would normally be available to the API as a dependency. The decorator would give me some additional powers I'd need in my integration tests to intercept calls to the underlying service, but I can't seem to properly decorate a normal service in ConfigureTestServices, as my current setup will give me:
An exception of type 'System.InvalidOperationException' occurred in Microsoft.Extensions.DependencyInjection.Abstractions.dll but was not handled in user code
No service for type 'Foo.Web.BarService' has been registered.
To reproduce this, I've just used VS2019 to create a fresh ASP.NET Core 2.2 API Foo.Web project...
// In `Startup.cs`:
services.AddScoped<IBarService, BarService>();
public interface IBarService
{
string GetValue();
}
public class BarService : IBarService
{
public string GetValue() => "Service Value";
}
[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
private readonly IBarService barService;
public ValuesController(IBarService barService)
{
this.barService = barService;
}
[HttpGet]
public ActionResult<string> Get()
{
return barService.GetValue();
}
}
...and a companion xUnit Foo.Web.Tests project I utilize a WebApplicationfactory<TStartup>...
public class DecoratedBarService : IBarService
{
private readonly IBarService innerService;
public DecoratedBarService(IBarService innerService)
{
this.innerService = innerService;
}
public string GetValue() => $"{innerService.GetValue()} (decorated)";
}
public class IntegrationTestsFixture : WebApplicationFactory<Startup>
{
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
base.ConfigureWebHost(builder);
builder.ConfigureTestServices(servicesConfiguration =>
{
servicesConfiguration.AddScoped<IBarService>(di
=> new DecoratedBarService(di.GetRequiredService<BarService>()));
});
}
}
public class ValuesControllerTests : IClassFixture<IntegrationTestsFixture>
{
private readonly IntegrationTestsFixture fixture;
public ValuesControllerTests(IntegrationTestsFixture fixture)
{
this.fixture = fixture;
}
[Fact]
public async Task Integration_test_uses_decorator()
{
var client = fixture.CreateClient();
var result = await client.GetAsync("/api/values");
var data = await result.Content.ReadAsStringAsync();
result.EnsureSuccessStatusCode();
Assert.Equal("Service Value (decorated)", data);
}
}
The behavior kind of makes sense, or at least I think it does: I suppose that the little factory lambda function (di => new DecoratedBarService(...)) in ConfigureTestServices cannot retrieve the concrete BarService from the di container because it's in the main service collection, not in the test services.
How can I make the default ASP.NET Core DI container provide decorator instances that have the original concrete type as their inner service?
Attempted solution 2:
I've tried the following:
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
base.ConfigureWebHost(builder);
builder.ConfigureTestServices(servicesConfiguration =>
{
servicesConfiguration.AddScoped<IBarService>(di
=> new DecoratedBarService(Server.Host.Services.GetRequiredService<BarService>()));
});
}
But this surprisingly runs into the same problem.
Attempted solution 3:
Asking for IBarService instead, like this:
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
base.ConfigureWebHost(builder);
builder.ConfigureTestServices(servicesConfiguration =>
{
servicesConfiguration.AddScoped<IBarService>(di
=> new DecoratedBarService(Server.Host.Services.GetRequiredService<IBarService>()));
});
}
Gives me a different error:
System.InvalidOperationException: 'Cannot resolve scoped service 'Foo.Web.IBarService' from root provider.'
Workaround A:
I can work around the issue in my small repro like this:
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
base.ConfigureWebHost(builder);
builder.ConfigureTestServices(servicesConfiguration =>
{
servicesConfiguration.AddScoped<IBarService>(di
=> new DecoratedBarService(new BarService()));
});
}
But this hurts a lot in my actual application, because BarService doesn't have a simple parameterless constructor: it has a moderately complex dependency graph, so I really would like to resolve instances from the Startup's DI container.
PS. I've tried to make this question fully self-contained, but there's also a clone-and-run rep(r)o for your convenience.
Contrary to popular belief, the decorator pattern is fairly easy to implement using the built-in container.
What we generally want is to overwrite the registration of the regular implementation by the decorated one, making use of the original one as a parameter to the decorator. As a result, asking for an IDependency should lead to a DecoratorImplementation wrapping the OriginalImplementation.
(If we merely want to register the decorator as a different TService than the original, things are even easier.)
public void ConfigureServices(IServiceCollection services)
{
// First add the regular implementation
services.AddSingleton<IDependency, OriginalImplementation>();
// Wouldn't it be nice if we could do this...
services.AddDecorator<IDependency>(
(serviceProvider, decorated) => new DecoratorImplementation(decorated));
// ...or even this?
services.AddDecorator<IDependency, DecoratorImplementation>();
}
The above code works once we add the following extension methods:
public static class DecoratorRegistrationExtensions
{
/// <summary>
/// Registers a <typeparamref name="TService"/> decorator on top of the previous registration of that type.
/// </summary>
/// <param name="decoratorFactory">Constructs a new instance based on the the instance to decorate and the <see cref="IServiceProvider"/>.</param>
/// <param name="lifetime">If no lifetime is provided, the lifetime of the previous registration is used.</param>
public static IServiceCollection AddDecorator<TService>(
this IServiceCollection services,
Func<IServiceProvider, TService, TService> decoratorFactory,
ServiceLifetime? lifetime = null)
where TService : class
{
// By convention, the last registration wins
var previousRegistration = services.LastOrDefault(
descriptor => descriptor.ServiceType == typeof(TService));
if (previousRegistration is null)
throw new InvalidOperationException($"Tried to register a decorator for type {typeof(TService).Name} when no such type was registered.");
// Get a factory to produce the original implementation
var decoratedServiceFactory = previousRegistration.ImplementationFactory;
if (decoratedServiceFactory is null && previousRegistration.ImplementationInstance != null)
decoratedServiceFactory = _ => previousRegistration.ImplementationInstance;
if (decoratedServiceFactory is null && previousRegistration.ImplementationType != null)
decoratedServiceFactory = serviceProvider => ActivatorUtilities.CreateInstance(
serviceProvider, previousRegistration.ImplementationType, Array.Empty<object>());
if (decoratedServiceFactory is null) // Should be impossible
throw new Exception($"Tried to register a decorator for type {typeof(TService).Name}, but the registration being wrapped specified no implementation at all.");
var registration = new ServiceDescriptor(
typeof(TService), CreateDecorator, lifetime ?? previousRegistration.Lifetime);
services.Add(registration);
return services;
// Local function that creates the decorator instance
TService CreateDecorator(IServiceProvider serviceProvider)
{
var decoratedInstance = (TService)decoratedServiceFactory(serviceProvider);
var decorator = decoratorFactory(serviceProvider, decoratedInstance);
return decorator;
}
}
/// <summary>
/// Registers a <typeparamref name="TService"/> decorator on top of the previous registration of that type.
/// </summary>
/// <param name="lifetime">If no lifetime is provided, the lifetime of the previous registration is used.</param>
public static IServiceCollection AddDecorator<TService, TImplementation>(
this IServiceCollection services,
ServiceLifetime? lifetime = null)
where TService : class
where TImplementation : TService
{
return AddDecorator<TService>(
services,
(serviceProvider, decoratedInstance) =>
ActivatorUtilities.CreateInstance<TImplementation>(serviceProvider, decoratedInstance),
lifetime);
}
}
This seems like a limitation of the servicesConfiguration.AddXxx method which will first remove the type from the IServiceProvider passed to the lambda.
You can verify this by changing servicesConfiguration.AddScoped<IBarService>(...) to servicesConfiguration.TryAddScoped<IBarService>(...) and you'll see that the original BarService.GetValue is getting called during the test.
Additionally, you can verify this because you can resolve any other service inside the lambda except the one you're about to create/override. This is probably to avoid weird recursive resolve loops which would lead to a stack-overflow.
There's actually a few things here. First, when you register a service with an interface, you can only inject that interface. You are in fact saying: "when you see IBarService inject an instance of BarService". The service collection doesn't know anything about BarService itself, so you cannot inject BarService directly.
Which leads to the second issue. When you add your new DecoratedBarService registration, you now have two registered implementations for IBarService. There's no way for it to know which to actually inject in place of IBarService, so again: failure. Some DI containers have specialized functionality for this type of scenario, allowing you to specify when to inject which, Microsoft.Extensions.DependencyInjection does not. If you truly need this functionality, you can use a more advanced DI container instead, but considering this is only for testing, that would like be a mistake.
Third, you have a bit of a circular dependency here, as DecoratedBarService itself takes a dependency on IBarService. Again, a more advanced DI container can handle this sort of thing; Microsoft.Extensions.DependencyInjection cannot.
Your best bet here is to use an inherited TestStartup class and factor out this dependency registration into a protected virtual method you can override. In your Startup class:
protected virtual void AddBarService(IServiceCollection services)
{
services.AddScoped<IBarService, BarService>();
}
Then, where you were doing the registration, call this method instead:
AddBarService(services);
Next, in your test project create a TestStartup and inherit from your SUT project's Startup. Override this method there:
public class TestStartup : Startup
{
protected override void AddBarService(IServiceCollection services)
{
services.AddScoped(_ => new DecoratedBarService(new BarService()));
}
}
If you need to get dependencies in order to new up any of these classes, then you can use the passed in IServiceProvider instance:
services.AddScoped(p =>
{
var dep = p.GetRequiredService<Dependency>();
return new DecoratedBarService(new BarService(dep));
}
Finally, tell your WebApplicationFactory to use this TestStartup class. This will need to be done via the UseStartup method of the builder, not the generic type param of WebApplicationFactory. That generic type param corresponds to the entry point of the application (i.e. your SUT), not which startup class is actually used.
builder.UseStartup<TestStartup>();
All the other answers were very helpful:
#ChrisPratt clearly explains the underlying problem, and offers a solution where Startup makes the service registration virtual and then overrides that in a TestStartup that is forced upon the IWebHostBuilder
#huysentruitw answers as well that this is a limitation of the underlying default DI container
#KirkLarkin offers a pragmatic solution where you register BarService itself in Startup and then use that to overwrite the IBarService registration completely
And still, I'd like to offer yet another answer.
The other answers helped me find the right terms to Google for. Turns out, there is the "Scrutor" NuGet package which adds the needed decorator support to the default DI container. You can test this solution yourself as it simply requires:
builder.ConfigureTestServices(servicesConfiguration =>
{
// Requires "Scrutor" from NuGet:
servicesConfiguration.Decorate<IBarService, DecoratedBarService>();
});
Mentioned package is open source (MIT), and you can also just adapt only the needed features yourself, thus answering the original question as it stood, without external dependencies or changes to anything except the test project:
public class IntegrationTestsFixture : WebApplicationFactory<Startup>
{
protected override void ConfigureWebHost(IWebHostBuilder builder)
{
base.ConfigureWebHost(builder);
builder.ConfigureTestServices(servicesConfiguration =>
{
// The chosen solution here is adapted from the "Scrutor" NuGet package, which
// is MIT licensed, and can be found at: https://github.com/khellang/Scrutor
// This solution might need further adaptation for things like open generics...
var descriptor = servicesConfiguration.Single(s => s.ServiceType == typeof(IBarService));
servicesConfiguration.AddScoped<IBarService>(di
=> new DecoratedBarService(GetInstance<IBarService>(di, descriptor)));
});
}
// Method loosely based on Scrutor, MIT licensed: https://github.com/khellang/Scrutor/blob/68787e28376c640589100f974a5b759444d955b3/src/Scrutor/ServiceCollectionExtensions.Decoration.cs#L319
private static T GetInstance<T>(IServiceProvider provider, ServiceDescriptor descriptor)
{
if (descriptor.ImplementationInstance != null)
{
return (T)descriptor.ImplementationInstance;
}
if (descriptor.ImplementationType != null)
{
return (T)ActivatorUtilities.CreateInstance(provider, descriptor.ImplementationType);
}
if (descriptor.ImplementationFactory != null)
{
return (T)descriptor.ImplementationFactory(provider);
}
throw new InvalidOperationException($"Could not create instance for {descriptor.ServiceType}");
}
}
There's a simple alternative to this that just requires registering BarService with the DI container and then resolving that when performing the decoration. All it takes is updating ConfigureTestServices to first register BarService and then use the instance of IServiceProvider that's passed into ConfigureTestServices to resolve it. Here's the complete example:
builder.ConfigureTestServices(servicesConfiguration =>
{
servicesConfiguration.AddScoped<BarService>();
servicesConfiguration.AddScoped<IBarService>(di =>
new DecoratedBarService(di.GetRequiredService<BarService>()));
});
Note that this doesn't require any changes to the SUT project. The call to AddScoped<IBarService> here effectively overrides the one provided in the Startup class.
I am going to implement repository pattern in my asp.net core mvc application , for that i am trying my hands on a simple demo application which include repository and Unit of Work concept.
My First Repository
public interface ICustomerRepository
{
bool Add();
bool Update();
bool Delete();
}
and
public class CustomerRepository:ICustomerRepository
{
public bool Add()
{
return true;
}
public bool Update()
{
return true;
}
public bool Delete()
{
return true;
}
}
Second Repository
public interface IOrderRepository
{
bool Add();
bool Update();
bool Delete();
}
and
public class OrderRepository:IOrderRepository
{
public bool Add()
{
return true;
}
public bool Update()
{
return true;
}
public bool Delete()
{
return true;
}
}
IUnit Of Work
public interface IUnitOfWork
{
IOrderRepository Order {get;}
ICustomerRepository Customer { get; }
void Save();
void Cancel();
}
and
public class UnitOfWork:IUnitOfWork
{
public UnitOfWork(IOrderRepository order, ICustomerRepository customer)
{
Order = order;
Customer = customer;
}
public IOrderRepository Order { get; }
public ICustomerRepository Customer { get; }
public void Save() { }
public void Cancel() { }
}
And in my controller ,
public class HomeController : Controller
{
IUnitOfWork UW { get; }
public HomeController(IUnitOfWork uw)
{
UW = uw;
}
public IActionResult Index()
{
UW.Customer.Add();
UW.Order.Update();
UW.Save();
return View();
}
}
I will add more code later for dapper , but at least it should work wiyhout any error , but it give me error
InvalidOperationException: Unable to resolve service for type 'CoreTS.Repository.UnitOfWork.IUnitOfWork' while attempting to activate 'CoreTS.Controllers.HomeController'.
Someone suggested me to add IUnitOfWork as service in startup.cs under ConfigureService Method, as
services.AddSingleton<IUnitOfWork, UnitOfWork>();
And After Adding this another error
InvalidOperationException: Unable to resolve service for type 'CoreTS.Repository.Order.IOrderRepository' while attempting to activate 'CoreTS.Repository.UnitOfWork.UnitOfWork'.
To make it work i had to add other two repository also in startup.cs also
services.AddSingleton<IOrderRepository, OrderRepository>();
services.AddSingleton<ICustomerRepository, CustomerRepository>();
If there going to be n number of repository than i have to add everyone of them in startup.cs (according to this code ), what is the solution for that.
So
1.] What does these errors means ?
2.] What will be the correct configuration here ?
3.] What is the way to not to add n number of repository as service here ?
Note: As a mentioned already , this is just to understand the flow of pattern , i will add code for Dapper or EF Core later in this
What does these errors means ?
These error means that you are using the services through constructor Dependency Injection but you have not registered those services to DI resolver.
What will be the correct configuration here ?
What you have done is the correct way to resolve services.
What is the way to not to add n number of repository as service here?
You can extend the IServiceCollection as follows in a separate file.
public static class ServiceCollectionExtensions
{
public static IServiceCollection AddCustomServices(this IServiceCollection services,
IConfiguration configuration)
{
services.AddSingleton<IUnitOfWork, UnitOfWork>();
services.AddSingleton<IOrderRepository, OrderRepository>();
services.AddSingleton<ICustomerRepository, CustomerRepository>();
return services;
}
}
Then in the startup class as follows:
services.AddCustomServices(Configuration);
The constructor for HomeController takes an IUnitOfWork, so ASP.NET Core needs to know what instance to give it, that's why you specify it in ConfigureServices. But, your UnitOfWork class' constructor takes an IOrderRepository and an ICustomerRepository, and ASP.NET Core needs to know what instances of those to supply, so you have to specify those in ConfigureServices as well.
I think the configuration you've ended up at is correct, as far as it goes, but it doesn't address your next question...
There's already a problem with your pattern without the ASP.NET Core dependency injection issues. Your constructor for UnitOfWork takes 2 distinct parameters, one for each repository. If you want to have N different repositories, that constructor no longer works. Instead, maybe you need to introduce a "repository manager" class and just inject that into the constructor (add it in ConfigureServices too). Then you need to devise a relationship between UnitOfWork and RepositoryManager that allows UnitOfWork to work with any specific repository.
Well, the error message is quite meaningful. The DI container has to resolve the instance of IUnitOfWork which has two dependencies that are injected into its ctor. So DI container has to resolve these two as well.
There is no built-in functionality in asp.net-core that allows you to register all your repositories using pattern matching or something like that. You could register all dependencies one by one or use 3rd party libraries.
With Scrutor you can do something like this:
services.Scan(scan => scan
.FromAssemblyOf<OrderRepository>()
.AddClasses(classes => classes.AssignableTo<IRepository>())
.AsImplementedInterfaces()
.WithSingletonLifetime());
Note that for it to work all repositories must implement IRepository interface (which can be empty)
Conclusion:
If it's only a few dependencies I'd probably register them one by one however if you plan to add N repositories later - use 3rd party libs.
There is no service registered in the IoC container for IUnitOfWork/IOrderRepository. You solved this by registering these services using AddSingleton method.
Not sure what you mean by correct configuration, but using AddSingleton/AddTransient/AddScoped you are registering some classes as services in the IoC container. So when you inject something (for example into your HomeController), then you are using the interface mapped to some concrete implementation.
You have to register the service somehow, that is what you are doing with methods mentioned before. If you won't register it, it won't be resolved and you will get exceptions when trying to activate some other dependent services. If you want to register some services without doing it explicitely, you will have to scan the assembly and look for types that you want to register.
I generate a singleton at runtime
public void ConfigureServices(IServiceCollection services)
{
var applications = Utils.generateApplications()
services.AddSingleton<ApplicationModel[]>(applications);
services.AddMvc();
}
How can I later update this dependency injected ApplicationModel[] with a completely new ApplicationModel[]. I have a feature in my application that the user can use to trigger a data refresh on the applications, but how can I update the underlying injected Singleton so all future injections will use the updated applications? I have a function Utils.generateApplications() that gets an up to date list of applications and returns a ApplicationModel[]. How do I overwrite the old injected Singleton with a new object to be injected into future calls if that makes sense?
I have some code :
public void UpdateData()
{
var applications = Utils.generateApplications()
//How do I set applications to replace the injected singleton for all future injections?
}
You should use an additional layer of indirection. I think the simplest way is to use an abstract factory. Define an interface something like this:
interface IApplicationModelFactory
{
public ApplicationModel[] GetModel();
}
Define a second interface with the method (or methods) needed to update the model:
interface IApplicationModelUpdate
{
void UpdateModel();
}
You can then change your ApplicationModel[] registration from single instance to scoped and delegate to the factory:
var modelFactory = new ApplicationModelFactory();
services.AddSingleton<IApplicationModelFactory>(modelFactory);
services.AddSingleton<IApplicationModelUpdate>(modelFactory);
services.AddScoped<ApplicationModel[]>(provider =>
provider.GetRequiredService<IApplicationModelFactory>().GetModel());
Inject IApplicationModelUpdate into the types that update the model and ApplicationModel[] into the types that use it. This has the advantage that all types resolved for the same request will get a consistent view of the model, even if it changes in the middle of processing that request.
You could also inject IApplicationModelFactory into the consumer code, but I think injecting the model directly is better. Using the factory can lead to different bits of code seeing different models during the same request. The mutability of the model is also an implementation detail that consumer code shouldn't have to worry about.
I wouldn't monkey with dependency injection that way. Instead, inject a factory, and write whatever logic you need to return the proper instance.
Simple factory:
interface IApplicationModelFactory
{
ApplicationModel[] Model { get; }
}
class ApplicationModelFactory : IApplicationModelFactory
{
public ApplicationModel[] Model { get; set; }
}
Registration:
services.AddSingleton<IApplicationModelFactory>
(
new ApplicationModelFactory[] { Model = util.generateApplications() }
)
class receiving the injection:
class Foo
{
protected readonly IApplicationModelFactory _factory;
public Foo(IApplicationModelFactory injected)
{
_factory = injected;
}
protected ApplicationModel[] => _factory.Model;
public void Bar()
{
DoSomethingWithModel(this.ApplicationModel);
}
}
I want to configure MassTransit at one point in my code (using WebActivator) and configure the message handlers in another (a Ninject module). Is there a way I can achieve this? The documentation here shows how to perform what I need in one step, but to do anyhting else, it looks like I need to get an instance of a ServiceBusConfigurator, which doesn't seem to be available from the preexisting IServiceBus
Configuration and Creation of the IServiceBus cannot be separated.
That means, the only option you have is to gather the configuration information some more time before creating the bus.
As the doc you linked states, the meta data information made available by ninject is not sufficient to create the subscriptions. This basically means that you've got to create your own metadata model. Let's make an example, which can be used with single registrations but also with convention based registrations:
Hint: You should treat the following code snippets as psuedo code as i've written them from memory. It's highly likely that it won't compile.
Metadata Model
public class SubscriptionMetadata
{
public SubscriptionMetadata(Type consumer)
{
if(!typeof(IConsumer).IsAssignableFrom(consumer))
{
string message = string.Format(
"{0} does not implement {1}",
typeof(IConsumer).Name,
consumer.Name);
throw new ArgumentOutOfRangeException("consumer", message);
}
this.ConsumerType = consumer;
}
public Type ConsumerType { get; private set; }
}
Registration of Metadata
Now this can be used like this in a Ninject module:
Bind<SubscriptionMetadata>()
.ToConstant(new SubscriptionMetadata(typeof(FooConsumer));
If you're going to use it a lot i'd recommend writing an extension method:
public static class SubscriptionBindingExtensions
{
public static void BindConsumer<T>(this IBindingRoot bindingRoot)
where T : IConsumer
{
Bind<SubscriptionMetadata>()
.ToConstant(new SubscriptionMetadata(typeof(T));
}
}
and usage (#Module):
BindConsumer<FooConsumer>();
IServiceBus creation
Now you would adapt the IServiceBus creation as follows:
var kernel = new StandardKernel();
// 2nd Step left out: load all IModule`s ..
var bus = ServiceBusFactory.New(sbc =>
{
//other configuration options
foreach(var metadata in kernel.GetAll<SubscriptionMetadata>())
{
sbc.Subscribe(subs =>
{
subs.Consumer(metadata.ConsumerType, kernel)
});
}
});
Convention based binding of Consumers
It can also be used in conjunction with conventions by leveraging the IBindingCreator interface. If you wish, i can post an example.
I have an azure application developed using MVC Web API, and it uses Ninject as the dependency injection framework, here there are number of queues used to communicate with the other worker roles responsible for the background processing.
To be able to unit test I decided to wrap the QueueClient with class called QueueClientWrapper and use an interface named IQueueClientWrapper
the class and interface looks like follows,
public interface IQueueClientWrapper
{
void Send<T>(T message);
}
public class QueueClientWrapper : IQueueClientWrapper
{
private QueueClient _queueClient;
public QueueClientWrapper(QueueClient queueClient)
{
_queueClient = queueClient;
}
public void Send<T>(T message)
{
_queueClient.Send(new BrokeredMessage(message));
}
}
However the limitation of this approach is I need to pass the QueueClient into the constructor, which is not possible with the Ninject.
So I was thinking changing the interface like,
public interface IQueueClientWrapper
{
void Send<T>(string connectionString,string queueName,T message);
}
so that I can use Ninject to inject the QueueClientWrapper without needing to pass constructor argument,
The issue I have now is, usually it's not recommended to create multiple queue client objects and we have to re-use same instance. So what's the best way to address this (I thought of using a static Hashtable and use to store queue name, queue client pairs, but I'm not very happy with that approach either)?
Dealing with Dependency Injection and Azure Queue
This question is from 2014, but here is a 2022 answer
You will need these 2 official azure extensions :
Azure.Storage.Queues (Contains the queue service)
Microsoft.Azure.Functions.Extensions (Contains helpers for the Startup.cs)
Add this line to your Startup.cs in the Configure method :
builder.Services.AddAzureClients(builder =>
{
builder.AddQueueServiceClient(configuration.GetValue<string>("AzureWebJobsStorage"));
});
And the constructor where you want the service :
public QueueHandlingService(QueueServiceClient queueClient)
{
_queueClient = queueClient;
//Or _queueClient = queueClient.GetQueueClient("myqueue-items");
}
Here are the docs for :
AddAzureClients
AddQueueServiceClient