以编程方式更改Castle Windsor中的依赖项

Question

我有一个课程,呼吁互联网服务获取一些数据:

public class MarketingService
{
    private IDataProvider _provider;
    public MarketingService(IDataProvider provider)
    {
        _provider = provider;
    }

    public string GetData(int id)
    {
        return _provider.Get(id);
    }
}

目前我有两个提供程序:HttpDataProvider和FileDataProvider.通常我会连接到HttpDataProvider,但如果外部Web服务失败,我想更改系统以绑定到FileDataProvider.就像是:

public string GetData(int id)
{
    string result = "";

    try
    {
        result = GetData(id); // call to HttpDataProvider
    }
    catch (Exception)
    {
        // change the Windsor binding so that all future calls go automatically to the
        // FileDataProvier
        // And while I'm at it, retry against the FileDataProvider    
    }

    return result;
}

因此,当执行此操作时,所有将来的MarketingService实例都将自动连接到FileDataProvider.如何在飞行中更改Windsor绑定？

Answer 1

一种解决方案是使用选择器

public class ForcedImplementationSelector<TService> : IHandlerSelector
{
    private static Dictionary<Type, Type>  _forcedImplementation = new Dictionary<Type, Type>();

    public static void ForceTo<T>() where T: TService
    {
        _forcedImplementation[typeof(TService)] = typeof(T);
    }

    public static void ClearForce()
    {
        _forcedImplementation[typeof(TService)] = null;
    }

    public bool HasOpinionAbout(string key, Type service)
    {
        return service == typeof (TService);
    }

    public IHandler SelectHandler(string key, Type service, IHandler[] handlers)
    {
        var tService = typeof(TService);
        if (_forcedImplementation.ContainsKey(tService) && _forcedImplementation[tService] != null)
        {
            return handlers.FirstOrDefault(handler => handler.ComponentModel.Implementation == _forcedImplementation[tService]);
        }

        // return default
        return handlers[0];
    }
}

测试和使用

[TestFixture]
public class Test
{
    [Test]
    public void ForceImplementation()
    {
        var container = new WindsorContainer();

        container.Register(Component.For<IFoo>().ImplementedBy<Foo>());
        container.Register(Component.For<IFoo>().ImplementedBy<Bar>());

        container.Kernel.AddHandlerSelector(new ForcedImplementationSelector<IFoo>());

        var i = container.Resolve<IFoo>();
        Assert.AreEqual(typeof(Foo), i.GetType());

        ForcedImplementationSelector<IFoo>.ForceTo<Bar>();

        i = container.Resolve<IFoo>();
        Assert.AreEqual(typeof(Bar), i.GetType());


        ForcedImplementationSelector<IFoo>.ClearForce();

        i = container.Resolve<IFoo>();
        Assert.AreEqual(typeof(Foo), i.GetType());
    }
}