WCF avoiding too many endpoints for experts - wcf

I have a lot of businesses services already implemented, and I´m exposing them as services by WCF.
I don´t like the idea to have one endpoint to each service..... it could be a problem to maintain in the future as my repository grows.......
I´d like to know wcf´s experts opinions if the code below would be a good approach an them I can move ahead with this solution.
Business Service A:
[ServiceContract]
public interface IServiceA
{
[OperationContract]
object AddA(object a);
[OperationContract]
object Update();
}
Business Service B:
[ServiceContract]
public interface IServiceB
{
[OperationContract]
object AddB(object b);
[OperationContract]
object Update();
}
Concrete implementation for Service A
public class ConcreteServiceA : IServiceA
{
public object AddA(object a)
{
Console.WriteLine("ConcreateServiceA::AddA");
return null;
}
public object Update()
{
Console.WriteLine("ConcreateServiceA::Update");
return null;
}
}
Concrete implementation for Service B
public class ConcreteServiceB : IServiceB
{
public object AddB(object b)
{
Console.WriteLine("ConcreateServiceB::AddB");
return null;
}
public object Update()
{
Console.WriteLine("ConcreateServiceB::Update");
return null;
}
}
My single service is partial to separate concerns to each service.
Note that it´s constructors depends on both business services above, will be injection using IoC
Partial for constructors
public partial class WCFService
{
IServiceA _a;
IServiceB _b;
public WCFService()
: this(new ConcreteServiceA(), new ConcreteServiceB())
{
}
public WCFService(IServiceA serviceA, IServiceB serviceB)
{
_a = serviceA;
_b = serviceB;
}
}
Partial class implementing only IServiveA
public partial class WCFService : IServiceA
{
object IServiceB.AddB(object b)
{
return _b.AddB(b);
}
object IServiceB.Update()
{
return _b.Update();
}
}
Partial class implementing only IServiceB
public partial class WCFService : IServiceB
{
object IServiceA.AddA(object a)
{
return _a.AddA(a);
}
object IServiceA.Update()
{
return _a.Update();
}
}
And in the client side, I using like that:
var endPoint = new EndpointAddress("http://localhost/teste");
ChannelFactory<IServiceA> _factoryA = new ChannelFactory<IServiceA>(new BasicHttpBinding(), endPoint);
IServiceA serviceA = _factoryA.CreateChannel();
serviceA.Update();
var netTcpEndPoint = new EndpointAddress("net.tcp://localhost:9000/teste");
ChannelFactory<IServiceB> _factoryB = new ChannelFactory<IServiceB>(new NetTcpBinding(), netTcpEndPoint);
IServiceB serviceB = _factoryB.CreateChannel();
serviceB.Update();
I really appreciate any opinion or other suggestions.

There's nothing wrong with multiple endpoints - it's part of the process. What is wrong, however, is duplicating functionality over multiple endpoints. How many "UpdateThis's" or "AddThat's" developers need? This can get out of control and makes for a maintenance headache. Just look at your constructor, it will grow and grow as you add new services and consolidate them into one service.
Think coarse-grained not fine-grained.
As an alternative, maybe you can try passing request objects as a parameter and returning response objects. This approach may streamline your code and help you avoid the maintenance issues you mention in your post and gives you a suggestion.
So, it looks something like this:
// Your service will return a very generic Response object
public interface IService
{
Response YourRequest(Request request);
}
// Your service implementation
public partial class WCFService : IService
{
Response IService.YourRequest(Request request)
{
//inspect the Request, do your work based on the values
//and return a response object
}
}
// Your request object
public class Request()
{
object YourClass{get;set;}
DoWhat Action{get;set;} //enum, constants, string etc.
int ID {get; set;}
}
// Your response object
public class Response()
{
bool Success {get; set;}
}
// Create Request object
var request = new Request(){YourClass = YourClassName , Action DoWhat.Update(), ID=1};
// Your service call
var endPoint = new EndpointAddress("http://localhost/teste");
ChannelFactory<IService> _factory = new ChannelFactory<IService>(new BasicHttpBinding(), endPoint);
IService service = _factory.CreateChannel();
var response = service.YourRequest(request);
So, now you've removed the fine-grained approach and replaced it with course-grained one. Let me know if you'd like more detail.

Related

Using Castle Windsor WCF facility with WCF 4 REST service gives 'Could not find a component' error

As a long time reader of StackOverflow but not finding the solution to my problem here is my first attempt to ask a question, so don't be too harsh on me :-)
I have the following WCF 4 REST service definitions:
Service contract
namespace RestService2.Service
{
[ServiceContract]
public interface ISampleService
{
[WebGet(UriTemplate = "")]
List<SampleItem> GetCollection();
[WebInvoke(UriTemplate = "", Method = "POST")]
SampleItem Create(SampleItem instance);
[WebGet(UriTemplate = "?id={id}")]
SampleItem Get(int id);
[WebInvoke(UriTemplate = "?id={id}", Method = "PUT")]
SampleItem Update(int id, SampleItem instance);
[WebInvoke(UriTemplate = "?id={id}", Method = "DELETE")]
void Delete(int id);
}
}
Service implementation
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class SampleService : ISampleService
{
private IDatabase db;
public SampleService(IDatabase db)
{
this.db = db;
}
public SampleService()
{
}
public List<SampleItem> GetCollection()
{
return db.Items.Values.ToList();
}
public SampleItem Create(SampleItem instance)
{
// Add the new instance of SampleItem to the collection
db.Items.Add(instance.Id, instance);
return db.Items[instance.Id];
}
//..Rest omitted..
}
Database interface:
using RestService2.Entities;
namespace RestService2.Service
{
public interface IDatabase
{
Dictionary<int, SampleItem> Items { get; }
}
}
Database implementation:
public class Database : IDatabase
{
private Dictionary<int, SampleItem> items;
public Database()
{
}
public Dictionary<int, SampleItem> Items
{
get
{
return items;
}
}
}
..and the global.asax file
namespace RestService2.Web
{
public class Global : HttpApplication
{
static IWindsorContainer Container {get; set;}
void Application_Start(object sender, EventArgs e)
{
BuildContainer();
RegisterRoutes();
}
private void BuildContainer()
{
Container = new WindsorContainer();
Container.AddFacility<WcfFacility>()
.Register(Component.For<ISampleService>().ImplementedBy<SampleService>().Named("SampleService"))
.Register(Component.For<IDatabase>().ImplementedBy<Database>());
}
private void RegisterRoutes()
{
RouteTable.Routes.Add(new ServiceRoute("SampleService",
new DefaultServiceHostFactory(), typeof(SampleService)));
}
}
}
The service contract, service implementation, database interface and database implementation are in assembly A, SampleItem (an entity) is defined in assembly B and the global.asax.cs is in assembly C.
I have added references from assembly A and B to assembly C.
When I try to access the service help page (or any service method for that matter) I get the following error message: Could not find a component with type RestService2.Service.SampleService, RestService2.Service, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null, did you forget to register it?
Any idea what could be problem? How should i configure the container correctly?
Regards
I was able to build a REST service using the WCFIntegration facility, using both interfaces for registration and through the MVC routing mechanism.
// SVC Routes
routes.Add(new ServiceRoute("Example", new WindsorServiceHostFactory<RestServiceModel>(), typeof(IExample)));
Remember to register the service/implementation in Windsor before calling RegisterRoutes (where this code would be). Additionally, make sure you call this route registration before your default route, otherwise that will be used instead.
The service can then just be called via the route, ie:
http://localhost:80/Core/Example/GetAll/
since you registered the routing by concrete type
RouteTable.Routes.Add(new ServiceRoute("SampleService",
new DefaultServiceHostFactory(), typeof(SampleService)));
and as far as I remember you cannot do otherwise... I mean you cannot register by interface, you need to register into the container by concrete as well
instead of
.Register(Component.For<ISampleService>().ImplementedBy<SampleService>().Named("SampleService"))
try
.Register(Component.For<SampleService>().Named("SampleService"))

Wcf service inheritance (Extend a service)

The program I am working on exposes both callbacks and services using wcf.
Basically, what the services do is simply return some variables value. As for the callback, they simply update those variables.
I want to be able to expose one class containing only the services and one class containing the services and the callbacks.
For example :
[ServiceContract]
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceClass
{
[OperationContract]
public int getValue()
{
return mValue;
}
protected static int mValue;
};
[ServiceContract]
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceAndCallbackClass : ServiceClass
{
[OperationContract]
public bool subscribe()
{
// some subscribing stuff
}
public void MyCallback()
{
++mValue;
// Notify every subscriber with the new value
}
};
If I want only the services, I can use the base class. However, if I want to subscribe to the callback and use the service, I can use ServiceAndCallbackClass.
Is this possible ?
One solution I found :
Make 2 interfaces. The first one containing only the services and the second one inheriting from the first one and adding the callbacks.
An implementation class would implement the 2 interfaces.
Example :
[ServiceContract]
[ServiceKnownType(typeof(ICallback))]
public interface IService
{
[OperationContract]
int GetData();
}
[ServiceContract]
public interface ICallback : IService
{
[OperationContract]
public bool subscribe();
}
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceClass : IService, ICallback
{
public int getValue()
{
return mValue;
}
public bool subscribe()
{
// some subscribing stuff
}
public void myCallback()
{
++mValue;
// Notify every subscriber with the new value
}
protected static int;
};
[ServiceBehavior(InstanceContextMode=InstanceContextMode::Single, ConcurrencyMode=ConcurrencyMode::Multiple)]
public ServiceAndCallbackClass : ServiceClass
{
// Dummy implementation used to create second service
};
From there, we can create 2 services. One based on the implementation class and one based on the "Dummy" class. Each service would be created from a different interface and thus exposing different methods.

How do I solve the error that I received when implementing the callback method?

I am currently developing a WCF duplex service and I am trying to implement the callback method in my client app however there is a error of
'App.CallbackHandler' does not implement interface member IPostingServiceCallback.retrieveNotification(Service.Posting)'
the service contract for my service are as follow
[ServiceContract(SessionMode=SessionMode.Required , CallbackContract = typeof(IPostingServiceCallBack))]
public interface IPostingService
{
[OperationContract(IsOneWay = true)]
void postNotification(Posting post);
}
public interface IPostingServiceCallBack
{
[OperationContract]
String retrieveNotification(Posting post);
}
I have generated the proxy and added into the project file of my client and adding the endpoint address into the app.config.
EDIT
The code I have in my client app currently is
public class CallBackHandler : IPostingServiceCallback
{
public void retrieveNotification()
{
//planning to do something
}
}
Your client application needs to implement IPostingServiceCallBack and define the retrieveNotification method.
Say you have a client (not the proxy) that will be consuming your duplex service:
public class MyClient : IPostingServiceCallBack
{
public String retrieveNotification(Posting post)
{
// Implement your logic here
}
}
Note the above is a bare-bones example as a simple illustration. Your client will probably derive from another class as well (depending on whether it's ASP.NET, WinForms, WPF, etc).
Updated
You're still not implementing the method. Your callback interface is:
public interface IPostingServiceCallBack
{
[OperationContract]
String retrieveNotification(Posting post);
}
Your implementation is:
public class CallBackHandler : IPostingServiceCallback
{
public void retrieveNotification()
{
//planning to do something
}
}
You have public void retrieveNotification(), whereas the interface has String retrieveNotification(Posting post). The method signatures don't match.
You need to do:
public class CallBackHandler : IPostingServiceCallback
{
public String retrieveNotification(Posting post)
{
// planning to do something
}
}

DI in Service Contract WCF

Please find below my code. Employee class implements IEmployee interface.
namespace MiddleWare.ServiceContracts
{
[ServiceContract(Namespace = "http://mywebsite.com/MyProject")]
public interface IMiscellaneous
{
[OperationContract]
[ServiceKnownType(typeof(MiddleWare.Classes.Employee))]
IEnumerable<IEmployee> Search_Employee
(string SearchText);
}
namespace MiddleWare.ServiceClasses
{
public class Miscellaneous : IMiscellaneous
{
public IEnumerable<IEmployee> Search_Employee
(string SearchText)
{
List<IEmployee> emp = new List<IEmployee>();
IEmployee TempObject = (IEmployee)Activator.CreateInstance(typeof(IEmployee));
TempObject.EmployeeId = "12345678";
emp.Add(TempObject);
return emp;
}
}
}
As is visible the above code does compile but wont work because interface instance cannot be created.How can I achive DI(Dependency Injection) here...If I write..
IEmployee TempObject = (IEmployee)Activator.CreateInstance(typeof(Employee));
Then this class will be dependent not only on the Interface but also the class...assuming that one fine day Employee class becomes Employee2.There will be code changes at two places..
1)[ServiceKnownType(typeof(MiddleWare.Classes.Employee2))]
2)IEmployee TempObject = (IEmployee)Activator.CreateInstance(typeof(Employee2));
I want to avoid that. Can we do something at implementation of IOperationBehavior or is there a Ninject way of achieving this or am I trying to achieve impossible?
Consider a design change - Use the factory pattern to create an instance of your employee.
public EmployeeFactory : IEmployeeFactory
{
public IEmployee CreateEmployee()
{
return new Employee();
}
}
And introduce a dependency on the Factory from your middleware, so creating a new IEmployee becomes:
public class Miscellaneous : IMiscellaneous
{
private readonly IEmployeeFasctory _employeeFactory;
public class Miscellaneous(IEmployeeFactory employeeFactory)
{
_employeeFactory = employeeFactory;
}
public IEnumerable Search_Employee (string searchText)
{
List employees = new List();
IEmployee employee = _employeeFactory.CreateEmployee();
employee.EmployeeId = "12345678";
employees.Add(TempObject);
return employees;
}
And then you can inject your EmployeeFactory into Miscellaneous. And should Employee one day become deprecated and Employee2 comes along, just change the factory!
As rich.okelly points out in another answer, IEmployeeFactory should be used to create instances of the IEmployee interface, since IEmployee isn't a Service, but an Entity.
The IEmployeeFactory interface, on the other hand, is a Service, so should be injected into the service class using Constructor Injection. Here's a write-up of enabling Constructor Injection in WCF.
Had a discussion within the team.
1) Constructor based implementation is not comfortable..The service would be IIS hosted and consumed as a web-reference.Cannot ask client systems to provide FactoryImplementatedObjects in Miscellaneous class call.
2) Entity based factories is also not absolutely accurate.If I happen to have say 20 specific entities in my project like Employee,Material,Project,Location,Order then I need to have 20 Factories.Also the Miscellaneous class will have several custom constructors to support specific contract calls..
I have prepared a system which is working and DI is achieved to a great level but I feel like I am cheating OOPS..Doesnt feel correct at heart..but cannot be refuted to be wrong..Please check and let me know your comments.
I now have a IEntity Interface which is the base for all other Entities.
namespace BusinessModel.Interfaces
{
public interface IEntity
{
string EntityDescription { get; set; }
}
}
Hence forth all will implement this.
namespace BusinessModel.Interfaces
{
public interface IEmployee : IEntity
{
string EmployeeId { get; set ; }
}
}
namespace BusinessModel.Interfaces
{
public interface IProject : IEntity
{
string ProjectId { get; set; }
}
}
and so on..(Interface implementing interface..absolutely ridiculous,cheating but working)
Next,An Enum type is declared to have a list of all Entities...
namespace MiddleWare.Common
{
internal enum BusinessModel
{
IEmployee,
IProject
}
}
A DI Helper class is created which will henceforth be considered a part of Business Model and any changes to it (Implementation,Naming..) would be taken as a Business Shift.So if DIHelper class has to become DIHelper2 then this is like BIG.(Can this also be avoided??)
namespace MiddleWare.Common
{
internal sealed class DIHelper
{
internal static IEntity GetRequiredIEntityBasedObject(BusinessModel BusinessModelObject)
{
switch (BusinessModelObject)
{
case BusinessModel.IEmployee:
return new Employee();
}
return null;
}
}
}
Function is Self Explanatory...
So now finally,the contract and implementation...
namespace MiddleWare.ServiceContracts
{
[ServiceContract(Namespace = "http://mywebsite.com/MyProject")]
public interface IMiscellaneous
{
[OperationContract]
[ServiceKnownType(typeof(MiddleWare.Classes.Employee))]
IEnumerable<IEmployee> Search_Employee
(string SearchText);
}
}
namespace MiddleWare.ServiceClasses
{
public class Miscellaneous : IMiscellaneous
{
public IEnumerable<IEmployee> Search_Employee
(string SearchText)
{
List<IEmployee> IEmployeeList = new List<IEmployee>();
IEmployee TempObject = (IEmployee)DIHelper.GetRequiredIEntityBasedObject(MiddleWare.Common.BusinessModel.IEmployee);
TempObject.EmployeeId = "12345678";
IEmployeeList.Add(TempObject);
return IEmployeeList;
}
}
}
What do you say??
My Team is happy though :)
From your updated requirements, there is nothing related to DI in this question...
So, to create a type based on the service known types of a service contract you can use:
public class EntityLoader<TServiceContract>
{
private static readonly HashSet<Type> ServiceKnownTypes = new HashSet<Type>();
static EntityLoader()
{
var attributes = typeof(TServiceContract).GetMethods().SelectMany(m => m.GetCustomAttributes(typeof(ServiceKnownTypeAttribute), true)).Cast<ServiceKnownTypeAttribute>();
foreach (var attribute in attributes)
{
ServiceKnownTypes.Add(attribute.Type);
}
}
public TEntity CreateEntity<TEntity>()
{
var runtimeType = ServiceKnownTypes.Single(t => typeof(TEntity).IsAssignableFrom(t));
return (TEntity)Activator.CreateInstance(runtimeType);
}
}
Which is then useable like so:
[ServiceContract(Namespace = "http://mywebsite.com/MyProject")]
public interface IMiscellaneous
{
[OperationContract]
[ServiceKnownType(typeof(Employee))]
IEnumerable<IEmployee> SearchEmployee(string SearchText);
}
public class Miscellaneous : IMiscellaneous
{
private readonly EntityLoader<IMiscellaneous> _entityLoader = new EntityLoader<IMiscellaneous>();
public IEnumerable<IEmployee> SearchEmployee(string SearchText)
{
List<IEmployee> employees = new List<IEmployee>();
IEmployee employee = _entityLoader.CreateEntity<IEmployee>();
employee.EmployeeId = "12345678";
employees.Add(employee);
return employees;
}
}
Obviously, the above code assumes that ALL of your service entities will contain public parameterless constructors and that there will only be one ServiceKnownType that implements each interface.

RhinoMocks Testing callback method

I have a service proxy class that makes asyn call to service operation. I use a callback method to pass results back to my view model.
Doing functional testing of view model, I can mock service proxy to ensure methods are called on the proxy, but how can I ensure that callback method is called as well?
With RhinoMocks I can test that events are handled and event raise events on the mocked object, but how can I test callbacks?
ViewModel:
public class MyViewModel
{
public void GetDataAsync()
{
// Use DI framework to get the object
IMyServiceClient myServiceClient = IoC.Resolve<IMyServiceClient>();
myServiceClient.GetData(GetDataAsyncCallback);
}
private void GetDataAsyncCallback(Entity entity, ServiceError error)
{
// do something here...
}
}
ServiceProxy:
public class MyService : ClientBase<IMyService>, IMyServiceClient
{
// Constructor
public NertiAdminServiceClient(string endpointConfigurationName, string remoteAddress)
:
base(endpointConfigurationName, remoteAddress)
{
}
// IMyServiceClient member.
public void GetData(Action<Entity, ServiceError> callback)
{
Channel.BeginGetData(EndGetData, callback);
}
private void EndGetData(IAsyncResult result)
{
Action<Entity, ServiceError> callback =
result.AsyncState as Action<Entity, ServiceError>;
ServiceError error;
Entity results = Channel.EndGetData(out error, result);
if (callback != null)
callback(results, error);
}
}
Thanks
Played around with this a bit and I think I may have what you're looking for. First, I'll display the MSTest code I did to verify this:
[TestClass]
public class UnitTest3
{
private delegate void MakeCallbackDelegate(Action<Entity, ServiceError> callback);
[TestMethod]
public void CallbackIntoViewModel()
{
var service = MockRepository.GenerateStub<IMyServiceClient>();
var model = new MyViewModel(service);
service.Stub(s => s.GetData(null)).Do(
new MakeCallbackDelegate(c => model.GetDataCallback(new Entity(), new ServiceError())));
model.GetDataAsync(null);
}
}
public class MyViewModel
{
private readonly IMyServiceClient client;
public MyViewModel(IMyServiceClient client)
{
this.client = client;
}
public virtual void GetDataAsync(Action<Entity, ServiceError> callback)
{
this.client.GetData(callback);
}
internal void GetDataCallback(Entity entity, ServiceError serviceError)
{
}
}
public interface IMyServiceClient
{
void GetData(Action<Entity, ServiceError> callback);
}
public class Entity
{
}
public class ServiceError
{
}
You'll notice a few things:
I made your callback internal. You'll need to use the InternalsVisisbleTo() attribute so your ViewModel assembly exposes internals to your unit tests (I'm not crazy about this, but it happens in rare cases like this).
I use Rhino.Mocks "Do" to execute the callback whenever the GetData is called. It's not using the callback supplied, but this is really more of an integration test. I assume you've got a ViewModel unit test to make sure that the real callback passed in to GetData is executed at the appropriate time.
Obviously, you'll want to create mock/stub Entity and ServiceError objects instead of just new'ing up like I did.