In a multilayer application (ASP MVC: UI project, DAL project) i registered in web.config the components.
Now i have this problem: Unit of Work pattern has do be implemented and i need to get the current instance of a particular service. The registration of the services happened in the UI project, but i need to get the current instance of this service in the DAL project. How do i get this reference?
In the UI project i already needed a way to get something resolved:
container = new WindsorContainer(
new XmlInterpreter(new ConfigResource("castle"))
);
personRepository= container.Resolve<IPersonRepository>();
Would it be OK to use the same technique in the DAL project? If yes, should i write the configuration in a separate file, so that it can be accessed by all the layers(projects)?
Sorry for this (i think) naive question but it's my first project using Castle and i think i don't understand the big picture of it!
Code snippet would help a lot.
Thanks in advance!
In a nutshell: one container instance per application, one container configuration that has all the components you need for the application. If you need a service in your DAL, inject the appropriate service interface in your DAL class via constructor (if the dependency is required) or setter (if the dependency is optional).
Try really hard to avoid using a static IoC gateway, it hides the true dependencies of a component and it hampers testability.
See these related questions:
Usage of IoC Containers; specifically Windsor
Is it correct to have many Castle Windsor containers per application if those containers belong to different tiers?
Have a look at this article. It shows you how to write a static class that performs dependency resolution using Castle Windsor. You should consider putting this class in a separate project that can be referenced from both your UI and DAL projects to allow code reuse. As the article explains, your class should provide a bootstrapper facility that initializes your IoC container. In your case, this would look like:
public static class IoC
{
private WindsorContainer _container;
public static void Initialize()
{
_container = new WindsorContainer(
new XmlInterpreter(new ConfigResource("castle"))
);
}
}
The bootstrapper would be invoked from the application startup event in your UI projects Global.asax file.
The other methods for obtaining instances of objects from the container would be as per the article.
Related
I've been running into endless problems attempting to use Windsor with Web API and injecting HttpRequestMessage into downstream dependencies of a controller. Since I've tried all the matching answers on Stackoverflow, I'd like to ask the question in a different way:
In Castle Windsor, how can I resolve a component instance while supplying a value for a downstream dependency? That is, the supplied value is required by a component that is required by the component being resolved.
For context, I'm trying to inject HttpRequestMessage so that I can use it to resolve the request context (primarily to resolve an absolute URL).
Edit I'd also like to point out that I don't currently have a dependency on Web Host / System.Web and I'd rather not change that.
A proper approach is to
Create IMyDesiredRouteParameterProvider
Implement it. Get the current request inside it and get the url
Register it and inject it in the desired dependent class via constructor.
I made myself such an implementation and I can say that this way it works fine. You can make Web.Infrastructure assembly and put the implementation there. Or put both the interface and the implementation there if you are going to reference it from another web module.
using System;
using System.Web;
namespace RouteParameterProvider
{
interface IMyRouteParameterProvider
{
string GetRouteParameter();
}
public class ControllerActionMethodRouteParameterProvider : IMyRouteParameterProvider
{
public string GetRouteParameter()
{
string Parameter = HttpContext.Current.Request.RequestContext.RouteData.Values["controller"] as string;
if (string.IsNullOrEmpty(Parameter))
{
throw new InvalidOperationException();
}
return Parameter;
}
}
}
You can get every possible thing that the Request Context contains from :
HttpContext.Current.Request.RequestContext
And it will be better if you rethink your design decision :
I need HttpRequestMessage to be regstered prior to creating each
instance of SomethingController so that it will be available down at
the LinkGenerator layer.
Containers are to be initialized at runtime and then used to resolve.
I need HttpRequestMessage to be regstered prior to creating each
instance of SomethingController so that it will be available down at
the LinkGenerator layer.
It sounds like you want to register an item with the container at runtime, post-startup. In general, this is not a good practice--registration should be a discrete event that happens when the app is fired up, and the container's state should not be changed during runtime.
Dependency Injection is about resolving service components, not runtime state--state is generally passed via methods (method injection). In this case it sounds like your LinkGenerator component needs access to the ambient state of the request.
I'm not that familiar with HttpRequestMessage, but this answer seems to show that it is possible to retreive it from HttpContext.Current. You could make this a method on your LinkGenerator class, or wrap this call in a separate component that gets injected into LinkGenerator (HttpRequestMessageProvider?). The latter would be my preferred method, as it allows LinkGenerator to be more testable.
Given the lack of a clean way of doing this and Web API not providing information as to the hosted endpoint beyond per-request context objects, I ended up injecting the base url from configuration.
Is this library by Mark Seemann the answer? In the description he writes explicitly :
This approach enables the use of Dependency Injection (DI) because the
request can be injected into the services which require it.
Then gives an example :
// Inside an ApiController
var uri = this.Url.GetLink(a=> a.GetById(1337));
By which you can then pass the URL down the road in the service that you have injected in the controller.
UPDATE :
Mark Seemann wrote about the same exact problem here:
"Because HttpRequestMessage provides the context you may need to
compose dependency graphs, the best extensibility point is the
extensibility point which provides an HttpRequestMessage every time a
graph should be composed. This extensibility point is the
IHttpControllerActivator interface:..."
This way you can pass request context information to a component deep in the object graph by getting from the HttpRequestMessage and passing it to the DI container.
Just take a look at the interface of IHttpControllerActivator.
The WEB API framework gets the IHttpControllerActivator through DependencyResolver. You probably already replaced it by your CastleWindsorDependencyResolver. Now you have to implement and register your HttpControllerActivator and register it.
When the WEB API framework gets IHttpControllerActivator from DependencyResolver (your Castle Windsor DR) and calls IHttpControllerActivator.Create() it will pass you the HttpRequestMessage. You can get your info from there and pass it to the your CastleDR before you call Resolve(typeof(MyController)) which will resolve the whole object graph - that means you will have MyHttpContextInfo to inject in your XYZComponent deep in the resolution stack.
This way tou are passing the arguments in the last possible moment but it is still possible. In Castle Windsor I make such passing of arguments though CreationContext.AdditionalArguments["myArgument"];.
I'm using NServiceBus (3.2.2), RavenDB (1.2.2017-Unstable) and Windsor (3.0.0.4001) in an MVC 4 project.
I have a IHandleMessages class that handles 3 different messages, and that needs an IDocumentSession, and therefore defines a property such as:
public IDocumentSession DocumentSession { get; set; }
I've copied the RavenDbUnitOfWork implementation from NServiceBus' website
I've registered IDocumentStore, IDocumentSession and IManageUnitsOfWork in my Windsor container as follow:
container.Register(
Component
.For<IManageUnitsOfWork>()
.ImplementedBy<RavenUnitOfWork>()
.LifestyleTransient()
);
container.Register(
Component
.For<IDocumentStore>()
.UsingFactoryMethod(k => DocumentStoreHolder.DocumentStore)
.LifestyleSingleton(),
Component
.For<IDocumentSession>()
.UsingFactoryMethod(k => k.Resolve<IDocumentStore>().OpenSession())
.LifestyleTransient()
);
NServiceBus is configured to use my container:
Configure.With()
.CastleWindsorBuilder(container);
I'm encountering the problem that the UnitOfWork and the message handler receive different instances of the DocumentSession. This means that objects stored in the session in the message handler are not saved, since SaveChanges() is called on a different DocumentSession.
Removing the Transient lifestyle causes different kind of problems, that result in concurrency/conflicts when updating objects from RavenDb, since (probably) the message handler keeps getting the same instance of the DocumentSession, which holds a cached version of the updated object.
Update:
As suggested, I've tried changing the registration of the IDocumentSession in Windsor, to the Scope lifestyle, like this:
Component
.For<IDocumentSession>()
.UsingFactoryMethod(k => k.Resolve<IDocumentStore>().OpenSession())
.LifestyleScope()
This causes exceptions when the container tries to resolve the MVC Controller, saying that the scope was not found, and asking if I forgot to call BeginScope().
You need to have a scope of Per Message, not transient or singleton.
I am assuming that your mvc controller has a direct dependency on the IDocumentStore. You need to call container.BeginScope() before each request from the web. You can either do this as an action filter attribute http://msdn.microsoft.com/en-us/library/system.web.mvc.actionfilterattribute.aspx or as an AOP aspect on the controller itself http://cangencer.wordpress.com/2011/06/02/asp-net-mvc-3-aspect-oriented-programming-with-castle-interceptors/.
The issue is you need different lifestyles when using nservicebus in an asp.net mvc website when sharing the IDocumentSession in the same container.
For ASP.NET MVC you need a PerWebRequest lifestyle and for NServiceBus you need the Scoped lifestyle.
To do that i've used the hybrid lifestyle code in the castle contrib project:
https://github.com/castleprojectcontrib/Castle.Windsor.Lifestyles/tree/master/Castle.Windsor.Lifestyles
When calling from an ASP.NET context, it uses the WebRequestScopeAccessor. For NServicebus you need the LifetimeScopeAccessor. This is not in the contrib project, but is easy to add:
public class HybridPerWebRequestLifetimeScopeScopeAccessor : HybridPerWebRequestScopeAccessor
{
public HybridPerWebRequestLifetimeScopeScopeAccessor()
: base(new LifetimeScopeAccessor())
{
}
}
And in your registration code you need something like:
container.Register(Component.For<IDocumentSession>().LifestyleScoped<HybridPerWebRequestLifetimeScopeScopeAccessor>().UsingFactoryMethod(() => RavenDbManager.DocumentStore.OpenSession()));
And here's an implementation for Rhino Service Bus i used before switching to nservicebus:
https://gist.github.com/4655544
I am building a site using entity framework 4.1 and mvc3. I am using the Generic Repository pattern:
http://www.tugberkugurlu.com/archive/generic-repository-pattern-entity-framework-asp-net-mvc-and-unit-testing-triangle. I use ninject to inject my concretes repositories to the controllers.
My problem is that each of my dbcontext different and I cannot run complex queries without the code shouting something like "different contexts cannot be used in the same query". I tried using the "singleton" approach but then code shouted something like "tried to enter a disposed object (null reference exception)".
Does anyone have an idea of what I'm doing wrong?
The Singleton pattern is an anti-pattern that should be avoided. It leads to hard to test code with all kinds of side effects (for example, a disposed DbContext).
The UnitOfWork manages operations on different repositories. It will keep track of all the changes that are made and then it will write those changes in the right order to your database. The DbContext already implements the UnitOfWork pattern (Altough it's nicer to hide the DbContext behind a custom UnitOfWork interface).
If you are already using dependency injection trough NInject you are almost their! You should change the constructors of your Repository to take a DbContext:
public class MyRepository
{
private _unitOfWork;
public MyRepository(DbContext unitOfWork)
{
_unitOfWork = unitOfWork;
}
....
}
If you then wire the DbContext to NInject with a InRequestScope mode everything should work. Your DbContext will then be shared by all Repositories and Ninject will dispose of it at the end of your request.
Not sure if I'm getting your question or not, but your repositories should be able to work within a "Unit of Work" which would have a single dbcontext.
I find the best place to start this unit of work is on the begin request, which you can setup in your global.asax ( and the end request for tear down )
The app I inherited uses the fluent interface for configuring our Windsor container, and it's this big glob o' configuration that's pretty disgusting.
In the past I created an extension method container.AddModule and then created modules that were passed in the container and registered services a la StructureMap for the different "modules" of my system that need configuration.
container.AddModule(new FooModule());
...
public class FooModule : IWindsorModule
{
public Register(IWindsorContainer container)
{
container.Register(/*Windsor's Ridiculous Fluent Syntax*/);
}
}
Is that what facilities are in Windsor? Are the analogous to StructureMap modules or are they extension points for adding super-magic to Windsor?
What is the best-practice for making your container config more modular and less insane?
Check out IWindsorInstaller:
http://stw.castleproject.org/Windsor.Installers.ashx
http://www.castlecasts.com/Episodes/9/Show/using-windsor
Also if you're coming from StructureMap this article might be useful.
There's a thin line with Facilities but in general, facilities are intended to be used for more complex stuff that requires custom configuration / several internal components, etc.
I've got a bit of a problem. I'm working in the Castle Windsor IOC Container. Now what i wanted to do is just mess about with some AOP principles and what i specifically want to do is based on a method name perform some logging. I have been looking at Interceptors and at the moment i am using the IInterceptor interface implemented as a class to perform this logging using aspects. The issue is if i want to perform the logging on a specific method then it gets messy as i need to put in some logic into my implemented aspect to check the method name etc...
I have read that you can do all of this using Dynamic Proxies and the IInterceptorSelector interface and the IProxyGenerationHook interface. I have seen a few examples of this done on the net but i am quite confused how this all fits into the Windsor container. I mean i am using the windsor container which in my code is actually a ref to the IWindsorContainer interface to create all my objects. All my configuration is done in code rather than XML.
Firstly does anyone know of a way to perform method specific AOP in the windsor container besides the way i am currently doing it.
Secondly how do i use the Dynamic Proxy in the windsor container ?
Below i have added the code where i am creating my proxy and registering my class with
the interceptors
ProxyGenerator _generator = new ProxyGenerator(new PersistentProxyBuilder());
IInterceptorSelector _selector = new CheckLoggingSelector();
var loggingAspect = new LoggingAspect();
var options = new ProxyGenerationOptions(new LoggingProxyGenerationHook())
{ Selector = _selector };
var proxy = _generator.CreateClassProxy(typeof(TestClass), options, loggingAspect);
TestClass testProxy = proxy as TestClass;
windsorContainer.Register(
Component.For<LoggingAspect>(),
Component.For<CheckLoggingAspect>(),
Component.For<ExceptionCatchAspect>(),
Component.For<ITestClass>()
.ImplementedBy<TestClass>()
.Named("ATestClass")
.Parameters(Parameter.ForKey("Name").Eq("Testing"))
.Proxy.MixIns(testProxy));
The Test Class is below:
public class TestClass : ITestClass
{
public TestClass()
{
}
public string Name
{
get;
set;
}
public void Checkin()
{
Name = "Checked In";
}
}
as for the interceptors they are very simple and just enter a method if the name starts with Check.
Now when i resolve my TestClass from the container i get an error.
{"This is a DynamicProxy2 error: Mixin type TestClassProxy implements IProxyTargetAccessor which is a DynamicProxy infrastructure interface and you should never implement it yourself. Are you trying to mix in an existing proxy?"}
I know i'm using the proxy in the wrong way but as i haven't seen any concrete example in how to use a proxy with the windsor container it's kind of confusing.
I mean if i want to use the LoggingProxyGenerationHook which just tell the interceptors to first for methods that start with the word "check" then is this the correct way to do it or am i completely on the wrong path. I just went down the proxy way as it seems very powerfull and i would like to understand how to use these proxies for future programming efforts.
By using .Interceptors() you already are using Dynamic Proxy. When component has specified interceptors Windsor will create proxy for it, and use these interceptors for it. You can also use method .SelectedWith and .Proxy property to set other options you already know from DynamicProxy.
I just added a website about Windsor AOP to documentation wiki. There's not much there yet, but I (and Mauricio ;) ) will put there all the information you need. Take a look, and let us know if everything is clear, and if something is missing.