How to do IServiceLocator constructor injection via config file? - dependency-injection

Question

How to inject IServiceLocator to my class constructor?
When I tried to do this via my config, described above I got an Exception that it could not to create a RequestHandlersFactory class because unity could't find the constructor with serviceLocator and assemblyName.
I got two interfaces
public interface IPublicService
{
[OperationContract]
[ServiceKnownType("GetKnownTypes", typeof(KnownTypeProvider))]
Response Handle(Request request);
}
public interface IRequestHandlersFactory
{
IRequestHandler GetHandler(Type requestType);
IRequestHandler GetHandler<T>()
where T : Request;
IRequestHandler<T, TK> GetHandler<T, TK>()
where T : Request
where TK : Response;
}
and two classes:
public sealed class PublicService: IPublicService
{
private readonly IRequestHandlersFactory _requestHandlersFactory;
public PublicService(IRequestHandlersFactory requestHandlersFactory)
{
_requestHandlersFactory = requestHandlersFactory;
}
public Response Handle(Request request)
{
var handler = _requestHandlersFactory.GetHandler(request.GetType());
return handler.Handle(request);
}
}
public sealed class RequestHandlersFactory : IRequestHandlersFactory
{
private readonly IServiceLocator _serviceLocator;
private RequestHandlersFactory(IServiceLocator serviceLocator)
{
_serviceLocator = serviceLocator;
...
}
public RequestHandlersFactory(IServiceLocator serviceLocator, String assemblyName) : this(serviceLocator)
{
AddHandlersFromAssembly(Assembly.Load(assemblyName));
}
public RequestHandlersFactory(IServiceLocator serviceLocator, Assembly assembly) : this(serviceLocator)
{
AddHandlersFromAssembly(assembly);
}
...
}
Now I want to create unity config file:
<unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
<alias alias="IPublicService" type="MyAssembly.IPublicService, MyAssembly"/>
<alias alias="PublicService" type="MyAssembly.PublicService, MyAssembly"/>
<alias alias="IRequestHandlersFactory" type="MyAssembly.IRequestHandlersFactory, MyAssembly"/>
<alias alias="RequestHandlersFactory" type="MyAssembly.RequestHandlersFactory, MyAssembly"/>
<container>
<register type="IPublicService" mapTo="PublicService">
<lifetime type="singleton"/>
</register>
<register type="IRequestHandlersFactory" mapTo="RequestHandlersFactory">
<lifetime type="singleton"/>
<constructor>
<param name="assemblyName">
<value value="MyAssemblyWithHandlers" />
</param>
<param name="serviceLocator" dependencyName="WcfServiceLocator" dependencyType="Microsoft.Practices.ServiceLocation.IServiceLocator, Microsoft.Practices.ServiceLocation"/>
</constructor>
</register>
</container>
My config code:
var container = new UnityContainer();
//configure container
var unitySection = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
var serviceLocator = new UnityServiceLocator(container );
container.RegisterInstance<IServiceLocator>("WcfServiceLocator", serviceLocator, new ContainerControlledLifetimeManager());
unitySection.Configure(container);

Answer 1

Try swapping the order of the constructor parameters in the config file so they line up with the actual parameter list in the class.