I'm quite new at design patterns, and I want to understand, if there is a 'tree of responsibility' design pattern, as a variation of 'chain of responsibility'?
Yes. In addition to a simple Handler implementation https://www.dofactory.com/net/chain-of-responsibility-design-pattern
/// <summary>
/// The 'Handler' abstract class
/// </summary>
abstract class Handler
{
protected Handler successor;
public void SetSuccessor(Handler successor)
{
this.successor = successor;
}
public abstract void HandleRequest(int request);
}
You'd do something like this https://www.codeproject.com/Articles/20108/Extending-Chain-of-Responsibility-Design-Pattern:
public class IfHandler : Handler<string>
{
private Case1Handler case1Handler;
private Case2Handler case2Handler;
public IfHandler(Case1Handler case1, Case2Handler case2)
{
case1Handler = case1;
case2Handler = case2;
}
public override bool MustExecuteHandleActions(string request)
{
return false;
}
public override void PassRequestToNextHandlers(string request)
{
if (request != null)
case1Handler.Handle(request);
else
case2Handler.Handle(request);
}
}
Related
I´m developing an ASP.NET MVC Application, in which I use NHibernate and Ninject.
The Problem is caused by the following Controller:
public class ShoppingCartController : Controller
{
private readonly Data.Infrastructure.IShoppingCartRepository _shoppingCartRepository;
private readonly Data.Infrastructure.IShopItemRepository _shopItemRepository;
public ShoppingCartController(Data.Infrastructure.IShoppingCartRepository shoppingCartController,
Data.Infrastructure.IShopItemRepository shopItemRepository)
{
_shoppingCartRepository = shoppingCartController;
_shopItemRepository = shopItemRepository;
}
public ActionResult AddToShoppingCart(FormCollection formCollection)
{
var cartItem = new Data.Models.ShoppingCartItem();
cartItem.ChangeDate = DateTime.Now;
cartItem.ShopItem = _shopItemRepository.GetShopItem(SessionData.Data.Info, Convert.ToInt32(formCollection["shopItemId"]));
//IF I DONT´T CALL THE METHOD ABOVE, AddToCart works
_shoppingCartRepository.AddToCart(SessionData.Data.Info, cartItem);
//BUT IF I CALL THE GetShopItem METHOD I GET THE EXCEPTION HERE!
return RedirectToAction("Index", "Shop");
}
}
I know most of the Time this Exception is caused by wrong Mapping, but I´m pretty sure that my Mapping is right because the AddToCart-Method works if I don´t call GetShopItem...
So here is the Code of the ShopItemRepository:
public class ShopItemRepository : ReadOnlyRepository<ShopItem>, IShopItemRepository
{
public ShopItemRepository(IUnitOfWork uow) : base(uow)
{
}
public ShopItem GetShopItem(SessionParams param, int id)
{
return CurrentSession.QueryOver<ShopItem>()
.Where(x => x.ProcessId == param.ProcessId &&
x.CatalogueId == param.CatalogueId &&
x.Id == id)
.SingleOrDefault();
}
public IList<ShopItem> GetShopItems(SessionParams param)
{
return CurrentSession.GetNamedQuery("GetShopItems")
.SetParameter("requestor_id", param.RequestorId)
.SetParameter("recipient_id", param.RecipientId)
.SetParameter("process_id", param.ProcessId)
.SetParameter("catalogue_id", param.CatalogueId)
.List<ShopItem>();
}
}
And finally the Code of my UnitOfWork (basically it is just a Wrapper for the Session because I don´t want to reference NHibernate in my MVC Project)
public class UnitOfWork : IUnitOfWork, IDisposable
{
private NHibernate.ISession _currentSession;
public NHibernate.ISession CurrentSession
{
get
{
if(_currentSession == null)
{
_currentSession = SessionFactoryWrapper.SessionFactory.OpenSession();
}
return _currentSession;
}
}
public void Dispose()
{
if(_currentSession != null)
{
_currentSession.Close();
_currentSession.Dispose();
_currentSession = null;
}
GC.SuppressFinalize(this);
}
}
Addendum:
My NinjectWebCommon Class
public static class NinjectWebCommon
{
private static readonly Bootstrapper bootstrapper = new Bootstrapper();
/// <summary>
/// Starts the application
/// </summary>
public static void Start()
{
DynamicModuleUtility.RegisterModule(typeof(OnePerRequestHttpModule));
DynamicModuleUtility.RegisterModule(typeof(NinjectHttpModule));
bootstrapper.Initialize(CreateKernel);
}
/// <summary>
/// Stops the application.
/// </summary>
public static void Stop()
{
bootstrapper.ShutDown();
}
/// <summary>
/// Creates the kernel that will manage your application.
/// </summary>
/// <returns>The created kernel.</returns>
private static IKernel CreateKernel()
{
var kernel = new StandardKernel();
kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
RegisterServices(kernel);
return kernel;
}
/// <summary>
/// Load your modules or register your services here!
/// </summary>
/// <param name="kernel">The kernel.</param>
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<IUnitOfWork>().To<UnitOfWork>().InRequestScope();
kernel.Bind<Data.Infrastructure.ICatalogueRepository>().To<Data.Repositories.CatalogueRepository>();
kernel.Bind<Data.Infrastructure.ICategoryRepository>().To<Data.Repositories.CategoryRepository>();
kernel.Bind<Data.Infrastructure.IContactRepository>().To<Data.Repositories.ContactRepository>();
kernel.Bind<Data.Infrastructure.IProcessRepository>().To<Data.Repositories.ProcessRepository>();
kernel.Bind<Data.Infrastructure.IShopItemRepository>().To<Data.Repositories.ShopItemRepository>();
kernel.Bind<Data.Infrastructure.IShoppingCartRepository>().To<Data.Repositories.ShoppingCartRepository>();
}
}
IUnitOfWork is set to RequestScope so in the Case of ShoppingCartController, the two Repositories share the same UOW right?
Maybe this could cause the Problem?
Are you sure that this isn´t caused by wrong mapping? I had the same Issue and could resolve it by checking my mappings again!
I am running into the below error the first time my ViewModel is being instantiated by the SimpleIoC. I believe I have setup the container as it should be, but for some reason, I am still getting the below error. Any ideas or assistance would be very much appreciated.
Microsoft.Practices.ServiceLocation.ActivationException was unhandled by user code
HResult=-2146233088
Message=Type not found in cache: Windows.UI.Xaml.Controls.Frame.
Source=GalaSoft.MvvmLight.Extras
StackTrace:
at GalaSoft.MvvmLight.Ioc.SimpleIoc.DoGetService(Type serviceType, String key) in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 532
at GalaSoft.MvvmLight.Ioc.SimpleIoc.GetService(Type serviceType) in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 768
at GalaSoft.MvvmLight.Ioc.SimpleIoc.MakeInstance[TClass]() in c:\Users\Public\Downloads\CodePlex\MVVMLight\GalaSoft.MvvmLight\GalaSoft.MvvmLight.Extras (NET35)\Ioc\SimpleIoc.cs:line 708
InnerException:
Here are pieces of my code related to this:
ViewModelLocator.cs (Located in my Win8 project)
public class ViewModelLocator
{
/// <summary>
/// Initializes a new instance of the ViewModelLocator class.
/// </summary>
public ViewModelLocator()
{
ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);
if (ViewModelBase.IsInDesignModeStatic)
{
// Create design time view services and models
//SimpleIoc.Default.Register<IDataService, DesignDataService>();
}
else
{
// Create run time view services and models
//SimpleIoc.Default.Register<IDataService, DataService>();
SimpleIoc.Default.Register<INavigationService, NavigationService>();
SimpleIoc.Default.Register<IParseService, ParseService>();
SimpleIoc.Default.Register<IServiceHandler, ServiceHandler>();
}
SimpleIoc.Default.Register<MainViewModel>();
SimpleIoc.Default.Register<ActionViewModel>();
}
public MainViewModel MainVM
{
get
{
return ServiceLocator.Current.GetInstance<MainViewModel>();
}
}
public ActionViewModel ActionVM
{
get
{
return ServiceLocator.Current.GetInstance<ActionViewModel>();
}
}
public static void Cleanup()
{
// TODO Clear the ViewModels
}
}
MainViewModel.cs Constructor
public class MainViewModel : ViewModelBase
{
#region Variables
private readonly INavigationService _navigationService;
private readonly IParseService _parseService;
#endregion
/// <summary>
/// Initializes a new instance of the MainViewModel class.
/// </summary>
public MainViewModel(INavigationService navigationService, IParseService parseService)
{
if (IsInDesignMode)
{
// Code runs in Blend --> create design time data.
}
else
{
_navigationService = navigationService;
_parseService = parseService;
BuildCommonData();
}
}
I know this is long overdue, but here is the offending code in the implementation of my NavigationService class.
NavigationService class (Before)
public class NavigationService : INavigationService
{
/// <summary>
/// Gets the root frame.
/// </summary>
private Frame RootFrame;
public NavigationService(Frame rootFrame)
{
RootFrame = rootFrame;
}
public event NavigatingCancelEventHandler Navigating;
public void Navigate<T>(object parameter = null)
{
var type = typeof(T);
RootFrame.Navigate(type, parameter);
}
public void Navigate(string type, object parameter = null)
{
RootFrame.Navigate(Type.GetType(type), parameter);
}
public void GoBack()
{
if (RootFrame.CanGoBack)
{
RootFrame.GoBack();
}
}
public void GoForward()
{
if (RootFrame.CanGoForward)
{
RootFrame.GoForward();
}
}
}
I simply took out the constructor, and made the RootFrame private variable a property. Like so:
public class NavigationService : INavigationService
{
/// <summary>
/// Gets the root frame.
/// </summary>
private static Frame RootFrame
{
get { return Window.Current.Content as Frame; }
}
public event NavigatingCancelEventHandler Navigating;
public void Navigate<T>(object parameter = null)
{
var type = typeof(T);
RootFrame.Navigate(type, parameter);
}
public void Navigate(string type, object parameter = null)
{
RootFrame.Navigate(Type.GetType(type), parameter);
}
public void GoBack()
{
if (RootFrame.CanGoBack)
{
RootFrame.GoBack();
}
}
public void GoForward()
{
if (RootFrame.CanGoForward)
{
RootFrame.GoForward();
}
}
}
Simple, I know, but hope it's of some use.
I was getting the same error today in my Xamarin project. The actual error given was "System.Reflection.TargetInvocationException: 'Exception has been thrown by the target of an invocation.'" and then when I look up the InnerException I could see the actual error, which is Type not found in cache.
It was a silly mistake that I was using DataService instead of IDataService for the Constructor Dependency Injection.
public SearchViewModel(DataService dataService, IErrorLoggingService errorLoggingService, IDialogService dialogService, IResourceService resourceService, INavigationService navigationService) {
SearchCommand = new AsyncRelayCommand <SearchFilter>(SearchAsync);
DataService = dataService;
ErrorLoggingService = errorLoggingService;
DialogService = dialogService;
ResourceService = resourceService;
NavigationService = navigationService;
CancelCommand = new RelayCommand(Cancel);
}
And just for your information, this is how I registered my service.
SimpleIoc.Default.Register<IDataService, DataService>();
So the issue was fixed after changing to IDataService. Hope it helps.
I am developing a (hopefully) RESTful API using ServiceStack.
I noticed that most of my services look the same, for example, a GET method will look something like this:
try
{
Validate();
GetData();
return Response();
}
catch (Exception)
{
//TODO: Log the exception
throw; //rethrow
}
lets say I got 20 resources, 20 request DTOs, so I got about 20 services of the same template more or less...
I tried to make a generic or abstract Service so I can create inheriting services which just implement the relevant behavior but I got stuck because the request DTOs weren't as needed for serialization.
Is there any way to do it?
EDIT:
an Example for what I'm trying to do:
public abstract class MyService<TResponse,TRequest> : Service
{
protected abstract TResponse InnerGet();
protected abstract void InnerDelete();
public TResponse Get(TRequest request)
{
//General Code Here.
TResponse response = InnerGet();
//General Code Here.
return response;
}
public void Delete(TRequest request)
{
//General Code Here.
InnerDelete();
//General Code Here.
}
}
public class AccountService : MyService<Accounts, Account>
{
protected override Accounts InnerGet()
{
throw new NotImplementedException();//Get the data from BL
}
protected override void InnerDelete()
{
throw new NotImplementedException();
}
}
To do this in the New API we've introduced the concept of a IServiceRunner that decouples the execution of your service from the implementation of it.
To add your own Service Hooks you just need to override the default Service Runner in your AppHost from its default implementation:
public virtual IServiceRunner<TRequest> CreateServiceRunner<TRequest>(ActionContext actionContext)
{
return new ServiceRunner<TRequest>(this, actionContext); //Cached per Service Action
}
With your own:
public override IServiceRunner<TRequest> CreateServiceRunner<TRequest>(ActionContext actionContext)
{
return new MyServiceRunner<TRequest>(this, actionContext); //Cached per Service Action
}
Where MyServiceRunner is just a custom class implementing the custom hooks you're interested in, e.g:
public class MyServiceRunner<T> : ServiceRunner<T> {
public override void OnBeforeExecute(IRequestContext requestContext, TRequest request) {
// Called just before any Action is executed
}
public override object OnAfterExecute(IRequestContext requestContext, object response) {
// Called just after any Action is executed, you can modify the response returned here as well
}
public override object HandleException(IRequestContext requestContext, TRequest request, Exception ex) {
// Called whenever an exception is thrown in your Services Action
}
}
Also for more fine-grained Error Handling options check out the Error Handling wiki page.
My solution was to add an additional layer where I can handle Logic per entity:
Base Logic Sample:
public interface IEntity
{
long Id { get; set; }
}
public interface IReadOnlyLogic<Entity> where Entity : class, IEntity
{
List<Entity> GetAll();
Entity GetById(long Id);
}
public abstract class ReadOnlyLogic<Entity> : IReadOnlyLogic<Entity> where Entity : class, IEntity, new()
{
public IDbConnection Db { get; set; }
#region HOOKS
protected SqlExpression<Entity> OnGetList(SqlExpression<Entity> query) { return query; }
protected SqlExpression<Entity> OnGetSingle(SqlExpression<Entity> query) { return OnGetList(query); }
#endregion
public List<Entity> GetAll()
{
var query = OnGetList(Db.From<Entity>());
return Db.Select(query);
}
public Entity GetById(long id)
{
var query = OnGetSingle(Db.From<Entity>())
.Where(e => e.Id == id);
var entity = Db.Single(query);
return entity;
}
}
Then we can use hooks like:
public interface IHello : IReadOnlyLogic<Hello> { }
public class HelloLogic : ReadOnlyLogic<Hello>, IHello
{
protected override SqlExpression<Hello> OnGetList(SqlExpression<Hello> query)
{
return query.Where(h => h.Name == "Something");
}
}
Finally our service only calls our logic:
public class MyServices : Service
{
IHello helloLogic;
public object Get()
{
return helloLogic.GetAll();
}
}
I want to have my own AppContext in my ApiController (MVC4).
Should be something like
public class TestController : BaseApiController
{
[HttpGet]
public IEnumerable<TestVM> GetAll()
{
// the test service is injected with SimpleInjector
return _testService.GetAll(**base.AppContext**);
}
}
but the ApiController haven't access to the Session.
Are there any solutions to "activate" the Session for specific keys (because I don't want the whole Session)?
Or do you have any other idea (cache or cookie)?
This is the BaseApiController
public abstract class BaseApiController: ApiController
{
public IAppContext AppContext
{
get { return SessionState.AppContext; }
}
}
and this is my IAppContext (it will have more properties in the future)
public interface IAppContext
{
IIdentity User { get; }
/// <summary> Gets the user id. </summary>
/// <value>The user id.</value>
int IdUser { get; }
}
here the application module which is registered in the web.config
public class ApplicationModule : IHttpModule
{
// ...
SessionState.AppContext = _appContext.InitializeNew(
HttpRuntime.AppDomainAppPath, languages);
// ...
}
SessionState class to get the AppContext
public class SessionState : BaseSessionVariables
{
public static IAppContext AppContext
{
get { return SessionState.Get<IAppContext>("AppContext"); }
set { SessionState.Set("AppContext", value); }
}
}
here the BaseSessionVariables class
public static HttpSessionState GetSession()
{
return HttpContext.Current.Session;
}
protected static T Get<T>(string key) where T : class
{
var session = BaseSessionVariables.GetSession();
if (session == null)
{
throw new Exception("No session");
}
return (session[key] as T);
}
Thanks for your help!
Take a look at the implementation below. It should get you headed in the right direction.
Updated IAppContext - Added Setters
public interface IAppContext
{
IIdentity User { get; set; }
/// <summary> Gets the user id. </summary>
/// <value>The user id.</value>
int IdUser { get; set; }
}
Updated Base Controller - Instantiates a new AppContextImplemenation in the OnActionExecuting method
public abstract class BaseApiController: ApiController
{
public IAppContext AppContext {get; set;}
protected override void OnActionExecuting(
ActionExecutingContext filterContext)
{
AppContext = new AppContextImplementation();
}
}
New Class - implements IAppContext and wraps the HttpContext Session. For testing you can then create an TestAppContextImplementation that doesn't rely on Session but some other in memory storage mechanism.
public class AppContextImplementation : IAppContext
{
public IIdentity User
{
get { return HttpContext.Current.Session["User"] as IIdentity; }
set { HttpContext.Current.Session["User"] = value; }
}
int IdUser
{
get { return Convert.ToInt32(Session["IdUser"]); }
set { Session["IdUser"] = value; }
}
}
For ApiControllers, build yourself a DelegatingHandler and push all of your goodies onto request.Properties. You can then retrieve them from your request whether you are testing or running live. The benefit is that you then have zero dependency on Session in your Controller.
MessageHandler
public class ContextHandler : DelegatingHandler
{
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
// get the goodies to add onto the request
var goodies = /* call to goodieGoodieYumYum */
// add our goodies onto the request
request.Properties.Add(Constants.RequestKey_Goodies, goodies);
// pass along to the next handler
return base.SendAsync(request, cancellationToken);
}
}
Controller Action
var goodies = (List<Goodie>)Request.Properties[Constants.RequestKey_Goodies];
Does anyone have an implementation lying around of an auto-mock container using Rhino Mocks and NInject?
OK I built one myself using the Moq integration as a starting point. It is very simple. You need these 3 classes:
public class AutoMockingKernel : StandardKernel
{
private readonly IMockProvider _mockProvider;
public void Reset()
{
Components.Get<ICache>().Clear();
}
protected override bool HandleMissingBinding(Type service)
{
var isSelfBindable = TypeIsSelfBindable(service);
var binding = new Binding(service)
{
ProviderCallback = isSelfBindable
? StandardProvider.GetCreationCallback(service)
: _mockProvider.GetCreationCallback(),
IsImplicit = true
};
if (!isSelfBindable)
binding.ScopeCallback = ctx => null;
AddBinding(binding);
return true;
}
public AutoMockingKernel(IMockProvider mockProvider, INinjectSettings settings, params INinjectModule[] modules)
: base(settings, modules)
{
_mockProvider = mockProvider;
}
public AutoMockingKernel(IMockProvider mockProvider, params INinjectModule[] modules)
: base(modules)
{
_mockProvider = mockProvider;
}
}
internal class RhinoMockProvider : IProvider
{
public Type Type { get; private set; }
/// <summary>
/// Initializes a new instance of the <see cref="RhinoMockProvider"/> class.
/// </summary>
public RhinoMockProvider(Type type)
{
Type = type;
}
public object Create(IContext context)
{
return MockRepository.GenerateMock(Type, Type.EmptyTypes);
}
}
public class RhinoAutoMockProvider : IMockProvider
{
public Func<IContext, IProvider> GetCreationCallback()
{
return ctx => new RhinoMockProvider(ctx.Request.Service);
}
}
You can then create an auto-mocking kernel in your unit test like this:
[Test]
public void Test()
{
var kernel = new AutoMockingKernel(new RhinoAutoMockProvider());
... etc
}
There is a RhinoMocks integration extension available.