I have an Autofac container that uses "AnyConcreteTypeNotAlreadyRegisteredSource" to allow resolution of any concrete type without explicit need to register it. If I register a singleton instance of a concrete type using the RegisterInstance method, there are no issues with the resolution. However, if I create a child lifetime scope and do the same concrete type singleton instance registration, the child lifetime scope is not able to resolve the type anymore. It throws the following exception:
Autofac.Core.Activators.Reflection.NoConstructorsFoundException: 'No accessible constructors were found for the type 'AutofacTests.IssueTests+Manager'.'
Why is it even trying to instantiate the object when I have a singleton instance of that type registered already? It seems like this problem only comes when I try to resolve a concrete type instead of an interface.
Here is the test code that demonstrates the problem (The test method name and comments show what works and what does not):
using Autofac;
using Autofac.Features.ResolveAnything;
namespace AutofacTests
{
[TestClass]
public class IssueTests
{
private interface IPerson
{
}
private class Employee : IPerson
{
public Employee()
{
}
}
private class Manager : Employee
{
internal Manager(IPerson worker)
{
string s = "";
}
}
[TestMethod]
public void Resolution_ThatWorks()
{
ContainerBuilder builder = new ContainerBuilder();
var mgr = new Manager(null);
builder.RegisterInstance<IPerson>(mgr);
builder.RegisterInstance<Manager>(mgr);
using (var container = builder.Build())
{
var person = container.Resolve<Manager>();
Assert.IsNotNull(person, "Employee could not be resolved!");
}
}
[TestMethod]
public void ResolutionWithAnyTypeSource_ThatWorks()
{
ContainerBuilder builder = new ContainerBuilder();
// NOTE: This source registration does not impact the concrete type resolution when no child lifetime scope is involved.
builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
var mgr = new Manager(null);
builder.RegisterInstance<IPerson>(mgr);
builder.RegisterInstance<Manager>(mgr);
using (var container = builder.Build())
{
var person = container.Resolve<Manager>();
Assert.IsNotNull(person, "Employee could not be resolved!");
}
}
[TestMethod]
public void NestedResolution_ThatWorks()
{
ContainerBuilder builder = new ContainerBuilder();
using (var container = builder.Build())
{
void RegisterNestedServices(ContainerBuilder builder)
{
var mgr = new Manager(null);
builder.RegisterInstance<IPerson>(mgr);
builder.RegisterInstance<Manager>(mgr);
}
using (var childContainer = container.BeginLifetimeScope(RegisterNestedServices))
{
var person = childContainer.Resolve<Manager>();
Assert.IsNotNull(person, "Employee could not be resolved!");
}
}
}
[TestMethod]
public void NestedResolutionWithAnyTypeSource_ThatFails()
{
ContainerBuilder builder = new ContainerBuilder();
// NOTE: This source registration causes the resolution of a concrete type to fail in a child lifetime scope.
builder.RegisterSource(new AnyConcreteTypeNotAlreadyRegisteredSource());
using (var container = builder.Build())
{
void RegisterNestedServices(ContainerBuilder builder)
{
var mgr = new Manager(null);
builder.RegisterInstance<IPerson>(mgr);
builder.RegisterInstance<Manager>(mgr);
}
using (var childContainer = container.BeginLifetimeScope(RegisterNestedServices))
{
// Works
var person = childContainer.Resolve<IPerson>();
Assert.IsNotNull(person, "Person could not be resolved!");
// *** Fails ***
var emp = childContainer.Resolve<Manager>();
Assert.IsNotNull(emp, "Employee could not be resolved!");
}
}
}
}
}
Anyone has any idea what am I doing wrong or how to make this work in the child lifetime scopes?
Thanks.
It appears you're hitting this known issue where AnyConcreteTypeNotAlreadyRegisteredSource (ACTNARS) doesn't properly look at new registrations in child scopes.
At the time of this writing there is not a fix for it, but we'd love a PR to get it fixed. It's been open for a while now.
Related
I am integrating a mef-based ServiceLocator with Autofac. The current locator is able to compose an existing object by setting up a CompositionBatch and then injecting dependecies on the object. A simple repro:
public void MefCompositionContainer_CanComposeExistingObjects()
{
//1. Initialize Mef
var composablePartCatalogs = new List<ComposablePartCatalog>
{
new AssemblyCatalog(Assembly.GetExecutingAssembly())
//A lot more here..
};
var aggregateCatalog = new AggregateCatalog(composablePartCatalogs);
var container = new CompositionContainer(aggregateCatalog, true);
//2. Mef is able to compose existing object
var objectWithPropertyImport = new ClassWithPropertyImport();
Compose(container, objectWithPropertyImport);
objectWithPropertyImport.ImportOfMefExport.Should().NotBeNull();
}
static T Compose<T>(CompositionContainer container, T value)
{
var batch = new CompositionBatch();
batch.AddPart(value);
container.Compose(batch);
return value;
}
The following classes are required:
[Export]
public class MefExport { }
//Note that this class does not have the [Export] attribute
public class ClassWithPropertyImport
{
[Import]
public MefExport ImportOfMefExport { get; set; }
}
Is it possible to accomplish the same with Autofac? If so - what should be added / changed here to compose objectWithPropertyImport?
public void Autofac_CanComposeExistingObjects()
{
//1. Initialize Mef
var composablePartCatalogs = new List<ComposablePartCatalog>
{
new AssemblyCatalog(Assembly.GetExecutingAssembly())
//A lot more here..
};
var aggregateCatalog = new AggregateCatalog(composablePartCatalogs);
//2. Initialize Autofac and setup mef-integration
var builder = new ContainerBuilder();
builder.Register(c => new AutofacExport()).Exported(x => x.As<AutofacExport>());
builder.RegisterComposablePartCatalog(aggregateCatalog);
var ioc = builder.Build();
var objectWithPropertyImport = new ClassWithPropertyImport();
// Now what?
// Updated according to solution from Travis Illig.
// The following code works for me:
ioc.InjectProperties(objectWithPropertyImport);
objectWithPropertyImport.ImportOfMefExport.Should().NotBeNull();
}
If all you need to do is inject the properties of a new object using Autofac, then use the InjectProperties method on the lifetime scope / container.
using Autofac;
public class ClassWithPropertyImport
{
public MyExport ImportedProperty { get; set; }
}
public class MyExport { }
var builder = new ContainerBuilder();
builder.RegisterType<MyExport>();
var container = builder.Build();
using(var scope = container.BeginLifetimeScope())
{
var c = new ClassWithPropertyImport();
scope.InjectProperties(c);
c.ImportedProperty.Should().NotBeNull();
}
As long as the types you're injecting are registered with Autofac, it should work fine. You don't need the type of the thing you're injecting onto registered. (Note the ClassWithPropertyImport is not registered with Autofac but the MyExport class is.)
Keep in mind it does mean Autofac needs to resolve the MyExport type - so if it has dependencies, those do need to be registered with Autofac as well.
This is the first time I've used flash builder (I usually just use flash itself for all my AS stuff). I've got a bunch of non static classes and one of them has an issue passing a parameter from a constructor to a private var.
private function init():void
{
var keys:Primes = new Primes();
var keyArray:Array = [["kdc",keys.getRandomPrime()],["client",keys.getRandomPrime()],["server",keys.getRandomPrime()]];
trace(keyArray);
kdc = new KeyDistCentre(keyArray);
client = new Client(keyArray[1][1]);
server = new Server(keyArray[2][1]);
}
It's the kdc = new line which is causing an issue, when I pass keyArray into it it has a problem assigning the value to the private var in the class.
package
{
public class KeyDistCentre extends Client
{
private var keyList:Array = new Array();
public function KeyDistCentre(keys:Array)
{
super(keys[0][1]);
keyList = keys; **ERROR**
}
public function generateTicket():Ticket
{
return null;
}
}
}
The weird thing is even when I comment out all the problematic lines, the exact same error with line reference occurs...
Let's say I have the following classes Customer.cs, a context OfficeContext.cs, and a repository OfficeRepository.cs. Knowing that the context use a connection object, so it's advised to enclose it in a using statement:
public List<Customer> GetAllCustomersWithOrders()
{
using(var oContext = new OfficeContext())
{
//Code here....
}
}
My question is what if I want to re-use some of the code already in the repository? For instance, what if I want to display all the customers that ordered products but didn't receive them yet, do I need to duplicate the code?
public List<Customer> GetCustomersNotReceiveProducts()
{
using(var oContext = new OfficeContext())
{
//Re-use GetAllCustomersWithOrders() here???...
}
}
But as you can see, each time access a method, I also open instantiate a new context object. Is there any way to deal with that?
What I do is have my repositories implement IDisposable.
Then have two constructors (one default) that instaniates a new context that holds it as a class level variable. And another constructor that takes a context and uses that internally.
The on the dispose of the class the context is disposed (if the current repository instatiated it).
This removes the context out of the method level and moves it to the class level. My functions keep everything in IQueryable so one function can call another function and perform additional refinements before the database it hit.
Exmaple:
public class MemberRepository : IDisposable
{
OfficeContext db;
bool isExternalDb = false;
public MemberRepository()
{
db = new OfficeContext();
isExternalDb = false;
}
public MemberRepository(OfficeContext db)
{
this.db = db;
isExternalDb = true;
}
public IQueryable<Member> GetAllMembers()
{
var members= db.Members
return members;
}
public IQueryable<Member> GetActiveMembers()
{
var members = GetAllMembers();
var activeMembers = members.Where(m => m.isActive == true);
return activeMembers;
}
public void Dispose()
{
if (isExternalDb == false)
{
db.Dispose();
}
}
}
Then where I use the repository, I do a using at that level:
using(var memberRepository = new MemberRepository())
{
var members = memberRepository.GetActiveMembers();
}
I'd like to know how I can have Imports in my custom ExportProvider. Here's an example of what I'm trying to do:
public class MyExportProvider : ExportProvider
{
private List<Export> _exports;
[Import()]
private IConfig _config;
public MyExportProvider()
base()
{
_exports = new List<Export>();
}
protected override IEnumerable<Export> GetExportsCore(ImportDefinition definition,
AtomicComposition composition)
{
if (!_exports.Any())
Initialize();
return _exports.Where(x => definition.IsConstraintSatisfiedBy(s.Definition);
}
private void Initialize()
{
var contractName = typeof(MyObject).FullName;
var exportDefinition = new ExportDefinition(contractName, null);
var export = new Export(exportDefinition, () => new MyObject(_config));
_exports.Add(export);
}
}
I am adding the provider when I create the CompositionContainer.
Unfortunately, the import is never satisfied. I can see this by setting AllowDefaults = true so my provider is created, but _config is always null.
How can I configure the container and/or provider so the Import will be satisfied?
When you are adding your export provider you are still creating your composition container. Thus I don't see how you can use the not yet created composition container to import parts of your custom export provider.
What I would do is first create a temporary CompositionContainer that will be used to create MyExportProvider.
Afterwards use the MyExportProvider to create your second final CompositionContainer that will be used by the rest of the application.
EDIT:
// this is your real container, only shown here for reference
CompositionContainer container;
public void BootstrapContainerMethod()
{
// Replace this part with the catalogs required to create your export provider.
var catalog = new AggregateCatalog();
catalog.Catalogs.Add(new DirectoryCatalog("./bin", "*.dll"));
// Your temporary container, declared here in local scope
// will be disposed because of using
using (var bootstrapContainer = new CompositionContainer(catalog))
{
var myExportProvider = bootstrapContainer.GetExportedValue<IMyExportProvider>();
// create your real container and optionnally add catalogs (not shown here)
container = new CompositionContainer(myExportProvider);
}
}
You might also consider the problem from another angle. Do you really need to have imports in your custom ExportProvider? I do not know your requirements, but maybe you can make do without having imports.
As an alternative to the dual CompositionContainer solution, you could wire this up in a single export provider, and have it compose itself using the same container. As an example, I've defined the following contract and it's export:
public interface ILogger
{
void Log(string message);
}
[Export(typeof(ILogger))]
public class ConsoleLogger : ILogger
{
public void Log(string message)
{
Console.WriteLine(message);
}
}
And with my example ExportProvider, I expect to be able to import an instance of it:
public class TestExportProvider : ExportProvider
{
private readonly object _lock = new object();
private bool _initialised;
[Import]
public ILogger Logger { get; set; }
public void SetCompositionService(ICompositionService service)
{
if (service == null) throw new ArgumentNullException("service");
lock (_lock)
{
if (!_initialised)
{
InitialiseProvider(service);
}
}
}
private void InitialiseProvider(ICompositionService service)
{
service.SatisfyImportsOnce(this);
_initialised = true;
}
protected override IEnumerable<Export> GetExportsCore(ImportDefinition definition, AtomicComposition atomicComposition)
{
if (_initialised)
{
Logger.Log("Getting available exports for '" + definition.ContractName + "'");
// Do work here.);
return Enumerable.Empty<Export>();
}
return Enumerable.Empty<Export>();
}
}
I provide an instance of an ICompositionService, which CompositionContainer implements, and I perform a first-time initialisation when I call SetCompositionService. It checks to see if it has already been initialised, and if not, goes ahead and calls the SatisfyImportsOnce method on itself.
We would wire this up, something like this:
// Build our catalog.
var catalog = new AssemblyCatalog(typeof(Program).Assembly);
// Create our provider.
var provider = new TestExportProvider();
// Create our container.
var container = new CompositionContainer(catalog, provider);
// Register the composition service to satisfy it's own imports.
provider.SetCompositionService(container);
Obviously you wouldn't be able to use any imports and your ExportProvider will explicitly create for you, but for everything else, it should work.
Beginners question:
Given two classes: Myclass5 and Myclass6 how can one wire up following factory method (returned as Func)
such that
myclass5 and myclass6 instances and IMyClass that they depend on are all retrieved via autofac (assuming that these three instances are registered).
public static MyClass4 FactoryMethod(int nu)
{
if (nu == 1)
return new MyClass5(....);
if (nu == 4)
return new MyClass6(....);
throw new NotImplementedException();
}
public abstract class MyClass4
{
}
public class MyClass5 : MyClass4
{
public MyClass5(int nu, IMyClass a)
{
}
}
public class MyClass6 : MyClass4
{
public MyClass6(int nu, IMyClass a)
{
}
}
For FactoryMethod to be able to create the instances, it requires access to a container. I would suggest create a delegate type for the factory method, which makes it easy to take dependency on it. Registration goes like this:
var cb = new ContainerBuilder();
cb.RegisterType<SomeClass>().As<IMyClass>();
cb.RegisterType<MyClass5>();
cb.RegisterType<MyClass6>();
cb.Register((c, p) =>
{
var context = c.Resolve<IComponentContext>();
return new FactoryMethod(nu =>
{
var nuParameter = TypedParameter.From(nu);
switch (nu)
{
case 1:
return context.Resolve<MyClass5>(nuParameter);
case 4:
return context.Resolve<MyClass6>(nuParameter);
default:
throw new NotImplementedException();
}
});
});
var container = cb.Build();
At resolve time, you can then take a dependency on the FactoryMethod delegate type and use it to resolve instances:
var factory = container.Resolve<FactoryMethod>();
var instance5 = factory(1);
var instance6 = factory(1);
Note: the delegate instance we're creating needs a context. We cannot use the c parameter directly since that context is only temporary. Thus we must resolve a IComponentContext to "bake" into the lambda.
Update: if you would like to extract the factory implementation into a method that is not dependent on the container I would suggest the following:
public class FactoryMethodImpl
{
readonly Func<int, MyClass5> _factory5;
readonly Func<int, MyClass6> _factory6;
public FactoryMethodImpl(Func<int, MyClass5> factory5, Func<int, MyClass6> factory6)
{
_factory5 = factory5;
_factory6 = factory6;
}
public MyClass4 Create(int nu)
{
switch (nu)
{
case 1:
return _factory5(nu);
case 4:
return _factory6(nu);
default:
throw new NotImplementedException();
}
}
}
Now, change the registration code to this:
var cb = new ContainerBuilder();
cb.RegisterType<SomeClass>().As<IMyClass>();
cb.RegisterType<MyClass5>();
cb.RegisterType<MyClass6>();
cb.RegisterType<FactoryMethodImpl>().SingleInstance();
cb.Register(c=> new FactoryMethod(c.Resolve<FactoryMethodImpl>().Create));