When my WebAPI controller is called from a client, I run into the following errors:
ServiceLocatorImplBase.cs not found error
An exception of type 'Microsoft.Practices.ServiceLocation.ActivationException' occurred in Microsoft.Practices.ServiceLocation.dll but was not handled in user code
The WebAPI controllers use constructor injection to inject a repository dependency which should be resolved by StructureMap IoC. Interestingly, the same code runs fine on my another development machine. Here is my stack trace. Thanks for your help.
System.ArgumentNullException was unhandled by user code
HResult=-2147467261
Message=Value cannot be null.
Parameter name: httpContext
Source=System.Web
ParamName=httpContext
StackTrace:
at System.Web.HttpContextWrapper..ctor(HttpContext httpContext)
at WebApi2.DependencyResolution.StructureMapDependencyScope.get_HttpContext() in c:.........\WebApi2\DependencyResolution\StructureMapDependencyScope.cs:line 69
at WebApi2.DependencyResolution.StructureMapDependencyScope.get_CurrentNestedContainer() in c:.........\WebApi2\DependencyResolution\StructureMapDependencyScope.cs:line 55
at WebApi2.DependencyResolution.StructureMapDependencyScope.DisposeNestedContainer() in c:.........\WebApi2\DependencyResolution\StructureMapDependencyScope.cs:line 90
at WebApi2.DependencyResolution.StructureMapDependencyScope.Dispose() in c:.........\WebApi2\DependencyResolution\StructureMapDependencyScope.cs:line 85
at WebApi2.App_Start.StructuremapMvc.End() in c:.........\WebApi2\App_Start\StructuremapMvc.cs:line 44
Thanks for your reply. Both machines are running integrated mode. The error is really misleading and threw me off to a wrong track. I spent hours trying to find where this ServiceLocatorImplBase.cs resides. I happened to look into the deeply nested inner exceptions, and found that the inner most exception (5th level) complains some entities generated by POCO generator have no identity key. This is because I manually added the foreign key relationship among some entities with
public virtual RelatedEntity1 {get;set;}
public virtual RelatedEntity2 {get;set;}
without setting [key] attributes in the related entities. I am not sure if this can be fixed but the exception message should not lead people to the wrong track.
The problem you are running into is because you are attempting to resolve HttpContext at the point in time that the application is composed (typically done in the Application_Start event of Global.asax). HttpContext is part of the application's runtime state. It is null at the point in time when the application is being composed.
The reason why it seems to work in your development environment is likely because your development environment's application pool is running in classic mode. Most likely the other environments are (correctly) running in integrated mode. So, this is a design issue, not a problem with deployment as you might expect.
The solution is to use an Abstract Factory so you can defer instantiating of the HttpContextWrapper until runtime. Then you can inject the abstract factory rather than HttpContextWrapper into your services.
public interface IHttpContextFactory
{
HttpContextBase Create();
}
public class HttpContextFactory
: IHttpContextFactory
{
public HttpContextBase Create()
{
return new HttpContextWrapper(HttpContext.Current);
}
}
See this answer and this answer for a complete examples including usage.
Related
all. I am getting started with NServiceBus and have a pretty good handle on the basics thanks to Pluralsight and the internet. I have an stock MVC 4 project and I have setup dependency injection for my controllers (thanks to this blog post).
Here is how I have my bus setup in Global.asax:
_bus = Configure.With()
.DefaultBuilder()
.ForMVC()
.Log4Net()
.XmlSerializer()
.MsmqTransport()
.UnicastBus()
.SendOnly();
I am assigning it to a local private variable because I need access to the bus in Global so I can do some stuff on Session_End. However, when I run, I get the following error:
The requested service 'System.Web.Mvc.IControllerFactory' has not been
registered. To avoid this exception, either register a component to
provide the service, check for service registration using
IsRegistered(), or use the ResolveOptional() method to resolve an
optional dependency.
According to my stack trace, the failure point is when Autofac tries to resolve the type. For the sake of sanity, I removed the private variable and used just the Configure statement, same thing. I also have Ninject wired up in this app because that is my IoC of choice. Thinking that it was interfering with Autofac in some way, I removed Ninject from the equation, still not working.
So my question is, what am I doing wrong? Am I missing something? This is my first time with NServiceBus, but from everything I've seen, this should just work. Any info would be super helpful. Thanks.
Have a look at our MVC4 sample (this is running against v4, the next major release):
https://github.com/NServiceBus/NServiceBus/tree/develop/Samples/Messaging.Msmq/MyWebClient
I found the solution from your code, John! Here was my issue. This is what I had in my Dependency Resolver Adapter:
public object GetService(Type serviceType)
{
_builder.Build(serviceType);
}
What I needed to do was what you did in your MVC4 example:
public object GetService(Type serviceType)
{
return (Configure.Instance.Configurer.HasComponent(serviceType)) ? _builder.Build(serviceType) : null;
}
Once I did that, it all sorted itself out. Thanks again for the help!
I am writing a service layer which uses Entity framework to get/set data from the database, and then pass it to an MVC web application. I am not able to decide what is the bext way to return database errors to the web application.
Should I throw an exception and the web application can handle it accordingly, or should I return a string/bool to convey that the database action has worked or not?
Any suggestion on what is the best practice?
Thanks
You can either not handle them in your service layer, or you can normalize them using an exception class that you will create. For example:
public class DatabaseException: Exception
{
public string TableName { get; private set; }
public DatabaseException(string tableName, Exception innerException)
:base("There a database error occured.", innerException)
{
TableName = tableName;
}
}
Simply add whatever information you require to the exception class as properties and initialize them in the constructor.
It's really not the best practice to inform the higher levels about exceptions with return values, since most of the methods are already returning some data.
You should not handle exception thrown out from web application, let exception thrown naturally, even from data access layer. With this way, it is easy for you for troubleshooting, esp in production stage. So, how to handle:
Use custom error page for exceptions thrown out.
Use HttpModule to log exception for troubleshooting. ELMAH, loggin module, works perfectly with ASP.NET MVC and alows you to view logs on web.
I'm trying to get myself familiar with MVC3 and autofac but I've encountered small problem that I'm having trouble resolving.
I am using autofac integrated with MVC3 and all works well, pages are loading correctly, dependencies are being injected and that's cool. What's bugging me is how to use autofac's Container or MVC's DependencyResover in class library project.
I'm trying to create static class that will help me handle domain events. I simply want to be able to call the method with event parameter and everything should be handeled by this class. Here is code:
public static IContainer Container { get; set; }
public static void Raise<T>(T e) where T : IDomainEvent
{
foreach (var eventHandler in DomainEventManager.Container.Resolve<IEnumerable<EventHandlers.Handles<T>>>())
{
eventHandler.Handle(e);
}
}
As you can see it's pretty straightforward and everything would work great if it wasn't MVC approach. Some of my dependencies are registeres as InstancePerHttpRequest (NHibernate' session), while other are registered as InstancePerDependency or SingleInstance. Thus when I try to use container created in my UI project, I get exception that there is no httpRequest tag available.
How can i reuse the Container created in web project to get access to all of it's features, including InstancePerHttpRequest and httpRequest tag?
Or maybe there is other solution to my problem? I was thinking about using delegate function to obtain event handlers, but I cannot (can I?) create generic delegate that I would not need to initialize with concrete type at time of assignment.
Why I want to do this using static class is basically every entity and aggregate or service needs to be able to raise domain event. Injecting EventManager into every one of these would be troublesome and static class is exactly what would resolve all my problems.
If anyone could help me get my head around it I would be grateful.
Cheers, Pako
You shouldn't be referencing your container directly from your app code. This looks like the Service Locator anti-pattern. The correct action is to pass your objects the services they need to do their jobs, usually done through constructor parameters. BUT... if you are going to insist on depending on a global static, then at least model EventManager as a singleton, such that usage would look like:
EventManager.Current.Raise<SomeEvent>(someObject);
and then you can set EventManager.Current equal to a properly constructed instance when your app is initialized.
this question Ninject Dependency Injection in MVC3 - Outside of a Controller is close to what I'm experiencing, but not quite.
I have an ASP.NET MVC3 site using Ninject 3 and it works wonderfully with constructor injection. All my dependencies are resolved, including those that pass in HttpContext.Current.
My issue is that in global.asax, I kick off a TaskManager class that periodically performs some tasks on a timer. Inside the TaskManager class, I don't have controllers, so if I need access to one of my dependencies (like my error logging service), I use a static wrapper class that has access to the kernel object:
var logger = MyContainer.Get<ILoggingService>();
logger.Error("error doing something...", ex);
The .Get method simply performs a kernel.Get call resolve my dependency. Works great every time I use this method on my other dependencies. However, ILoggingService has a dependency called MyWebHelper that is injected via it's constructor and includes HttpContext in it's constructor.
public class DefaultLogger : ILoggingService
{
public DefaultLogger(IRepository<Log> logRepository, IWebHelper webHelper)
{
_logRepository = logRepository;
_webHelper = webHelper;
}
}
public class MyWebHelper : IWebHelper
{
public MyWebHelper(HttpContext httpContext)
{
_httpContext = httpContext;
}
}
In the rest of my web site, this all works just fine because all the dependencies are injected into my MVC controllers. But what doesn't work is if I manually call my static wrapper class to get my dependencies that way. I get the error:
Error activating HttpContext using binding from HttpContext to method
Provider returned null.
So, it's not giving me an HttpContext like it does throughout the rest of my MVC application. I hope this makes sense, I'm not a ninject expert yet, but I'm trying...
My issue is that in global.asax, I kick off a TaskManager class that
periodically performs some tasks on a timer.
That's a bad idea as Phil Haack explains in details. Don't do this in your web application. Those recurring tasks should be done in a separate application (Windows Service or some console application which is scheduled to run at regular intervals).
Now the thing is that you are running background threads. Those background threads run outside of any user HTTP request and as a consequence HttpContext.Current is obviously null inside them. So even if you don't follow Phil Haack's advice and continue running background tasks in your ASP.NET application you will have to rearchitecture your method so that it no longer depends on any HttpContext because there's no such thing in those background threads.
I'm using StructureMap for IoC and it works fine for regular controllers but I can't make it work with Areas. I have the following AccountController in Administration Area:
public class AccountController : Controller
{
private readonly IFormsAuthenticationService formsService;
private readonly IMembershipService membershipService;
public AccountController(IFormsAuthenticationService formsService, IMembershipService membershipService)
{
this.formsService = formsService;
this.membershipService = membershipService;
}
...
}
And here's the error:
System.InvalidOperationException: An error occurred when trying to create a controller of type 'Foo.Areas.Administration.Controllers.AccountController'. Make sure that the controller has a parameterless public constructor. ---> System.MissingMethodException: No parameterless constructor defined for this object.
Any help would be greatly appreciated!
EDIT
StructureMap couldn't resolve MembershipProvider.
Here's the solution:
For<MembershipProvider>().Use(Membership.Providers["AspNetSqlMembershipProvider"]);
I doubt that this is a problem with areas because I am using them happily. It is more likely a pure IOC issue. You get this error when one of the injected services cannot be resolved by your container, which has the consequence that the container cannot match a signature for the constructor and tries to fall back to the empty constructor, which doesn't exist, rightly.
So, my first instinct would be to make sure that the two injected services are available. It is possible that one of them did not get created properly; a common cause is that the Membership provider cannot connect to its database, or similar.
For diagnosing, in your global.asax, after the container has been created, see if you can manually resolve those two services. I don't know SM, but something like:
var s = container.Resolve<IMembershipService>();
Satisfy yourself that both those services can be resolved.