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REST using the WCF Web API – refactoring to IoC style (Part 3) | Alexander Zeitler

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REST using the WCF Web API – refactoring to IoC style (Part 3) | Alexander Zeitler Toggle navigation Home Feed REST using the WCF Web API – refactoring to IoC style (Part 3) Written on April 18, 2011 Postings published on this series so far: Microsoft Web API -- the REST is washed-up by WCF (Part 1) REST using the WCF Web API -- Basics (Part2) REST using the WCF Web API -- refactoring to IoC style (Part 3) -- this one REST using the WCF Web API -- getting RESTful the BDD way (Part 4) REST using the WCF Web API -- getting increasingly RESTful responses (Part 5) REST using the WCF Web API -- Post it! (Part 6) Recap In the previous posting I gave you a short introduction to the shiny new WCF Web API from Microsoft. Of undertow the shown implementation is faraway from stuff a real world using sample -- so let's get started to move things forward. When looking then at our ContactsResource there is at least one thing that (hopefully) won't happen in real world code: [ServiceContract] public matriculation ContactsResource { [WebGet(UriTemplate = "")] public List<Contact> Get() { return new List<Contact>() { new Contact() { Id = 1, Name = "Glenn Block" }, new Contact() { Id = 2, Name = "Scott Hanselman" }, new Contact() { Id = 3, Name = "Scott Guthrie" } }; } } Moving forward As you can see, our List of Contacts is instantiated by hand. This for sure won't happen in a real world using happen considering it is likely that our contacts are stored in a database. Thus it will moreover be likely, that we'll have an Repository handling the CRUD-stuff versus this database. This will make our ContactsResource squint like this: [ServiceContract] public matriculation ContactsResource { [WebGet(UriTemplate = "")] public List<Contact> Get() { ContactRepository repository = new ContactRepository(); return repository.Get(); } } Whereas the ContactRepository looks like this: public matriculation ContactRepository { public List<Contact> Get() { return new List<Contact>() { new Contact() { Id = 1, Name = "Glenn Block" }, new Contact() { Id = 2, Name = "Scott Hanselman" }, new Contact() { Id = 3, Name = "Scott Guthrie" } }; } } Ok, this is much largest now. Guess what: It's faraway from that. It's not the fact, that we're new'ing up the Contacts themselves in the Repository as I don't want to lawmaking lanugo the well-constructed Repo for demo. Instead we didn't make an progress to the previous version as we're now simply instantiating the ContactRepository instead of the List of contacts inside our ContactsResource. In terms of testing we now have an dependency on the database by referencing to the touchable instance of our contacts repository. Your CI server may have other database settings (or plane worse: no database installed at all) than your local machine and your tests will goof miserably. Poor boy! In order to get rid of instantiating our repository inside our ContactsResource we will pass it to our constructor and remoter more, we'll pericope an interface tabbed IContactRepository in order to be worldly-wise to mart the touchable implementation of our repository whenever we want to. Doing it this way is a pattern tabbed dependency injection. Our updated code: [ServiceContract] public matriculation ContactsResource { readonly IContactRepository _contactRepository; public ContactsResource(IContactRepository contactRepository) { _contactRepository = contactRepository; } [WebGet(UriTemplate = "")] public List<Contact> Get() { return _contactRepository.Get(); } } public interface IContactRepository { List<Contact> Get(); } public matriculation ContactRepository : IContactRepository { public List<Contact> Get() { return new List<Contact>() { new Contact() { Id = 1, Name = "Glenn Block" }, new Contact() { Id = 2, Name = "Scott Hanselman" }, new Contact() { Id = 3, Name = "Scott Guthrie" } }; } } Yet, there's flipside problem: Who will instantiate our Repository? In terms of our ASP.NET MVC using hosting the ContactsResource, this is washed-up inside theGlobal.asax.cs file. You may remember ContactResourceFactory: public matriculation ContactResourceFactory : IResourceFactory { public object GetInstance(Type serviceType, InstanceContext instanceContext, HttpRequestMessage request) { return new ContactsResource(); } public void ReleaseInstance(InstanceContext instanceContext, object service) { throw new NotImplementedException(); } } Using this our lawmaking won't compile now, considering the instantiation of the ContactsResource is missing the IContactRepository instance. How do we pass it in then? One way could be -- as once written -- instantiate the dependency by ourselves inside the global.asax.cs. When having only a few dependencies, this may be ok. But speaking of a real using you'll have tons of them and you don't want to take superintendency of them the whole day. But we're fortunate. Lots of people ran into this surpassing and solved it by creating so tabbed IoC-Containers whose job is to create instances of our classes and handle dependencies between them. My favorite IoC-Container is LightCore and of course, it is misogynist through Nuget. After subtracting the Library Package Reference to our project, we'll update our lawmaking as follows -- starting with the updated RegisterRoutes method in Global.asax.cs: public static void RegisterRoutes(RouteCollection routes) { ContainerBuilder builder = new ContainerBuilder(); builder.Register<IContactRepository, ContactRepository>(); builder.Register<IResourceFactory, LightCoreResourceFactory>(); IContainer container = builder.Build(); var configuration = HttpHostConfiguration.Create() .SetResourceFactory(new LightCoreResourceFactory(container)); RouteTable.Routes.MapServiceRoute<ContactsResource>("contacts", configuration); } The LightCore IoC container mainly consists of a matriculation namely ContainerBuilder and an interface tabbed IContainer and works this way: A ContainerBuilder instance registers all dependencies by calling its Register method and passing in the interface name and the touchable type to be instantiated on using startup. When registration is done, an IContainer is build by the ContainerBuilder calling its Build method. The created container is passed into the LightCoreResourceFactory (formerly known as ContactResourceFactory). The fact that we're using the IoC container now, leads to a generic implementation of the LightCoreResourceFactory: public matriculation LightCoreResourceFactory : IResourceFactory { readonly IContainer _container; public LightCoreResourceFactory(IContainer container) { _container = container; } public object GetInstance(Type serviceType, InstanceContext instanceContext, HttpRequestMessage request) { return _container.Resolve(serviceType); } public void ReleaseInstance(InstanceContext instanceContext, object service) { throw new NotImplementedException(); } } As you can see, there's no reference to the ContactsResource or the ContactRepository at all inside the ResourceFactory. Thus we don't need flipside Factory when subtracting remoter Resources. In fact there's increasingly room for optimization as the SetResourceFactory method has an overload that allows us to inject the soul of the GetInstance and ReleaseInstance methods directly which makes the megacosm of the LightCoreResourceFactory obsolete and leads us to the pursuit configuration instantiation: var configuration = HttpHostConfiguration.Create() .SetResourceFactory((serviceType, instanceContext, request) => container.Resolve(serviceType), null); Did you notice that we didn't really speak well-nigh the WCF Web API itself since the whence of this post which simply highlights the fact that it does not get in way using this pattern -- well done. Speaking of done: we've finished flipside hands on lab on the WCF Web API -- thanks for reading. Next time we'll make it increasingly RESTful and add some tests in BDD style. Postings published on this series so far: Microsoft Web API -- the REST is washed-up by WCF (Part 1) REST using the WCF Web API -- Basics (Part2) REST using the WCF Web API -- refactoring to IoC style (Part 3) -- this one REST using the WCF Web API -- getting RESTful the BDD way (Part 4) REST using the WCF Web API -- getting increasingly RESTful responses (Part 5) REST using the WCF Web API -- Post it! (Part 6) .aspx&bgcolor=3169AD&fgcolor=FFFFFF&border=000000&cbgcolor=D4E1ED&cfgcolor=000000) Please enable JavaScript to view the comments powered by Disqus. Copyright © Alexander Zeitler 2003 - 2016 | Impressum