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.有人知道如何动态改变Windsor绑定吗？
解决方法
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());
}
}
