Question

我有一个简单的装饰类，如下所示。注意我的公共方法如何创建一个待装饰类的新实例，然后将调用转发给该实例。

这个类的问题是每当IMyService更新时，我也必须更新这个代理类。

public class MyProxyService : IMyService
{
    readonly IMyServiceFactory _realServiceFactory;

    public MyProxyService(IMyServiceFactory realServiceFactory)
    {
        _realServiceFactory = realServiceFactory;
    }

    private IMyService CreateRealService()
    {
        return _realServiceFactory.CreateRealService();
    }

    public int A()
    {
        return CreateRealService().A();
    }

    public int B(int b1)
    {
        return CreateRealService().B(int b1);
    }

    public int C(int c1, int c2)
    {
        return CreateRealService().C(c1,c2);
    }

    public int D(int d1, int d2, int d3)
    {
        return CreateRealService().D(d1,d2,d3);
    }
    public void E()
    {
        CreateRealService().E();
    }
}

我尝试使用Castle.DynamicProxy创建动态版本，到目前为止没有任何运气。

任何人都知道动态创建这样的装饰器的好方法吗？

Answer 1

我能够使用DynamicProxy.ProxyGenerator的{{3}}让这个工作正常。

我首先创建了一个动态代理工厂。这将返回一个代理对象，每个方法都将被提供的IInterceptor：

拦截

public class MyDynamicallyDecoratedServiceClientFactory
{
    readonly ProxyGenerator _proxyGenerator;
    readonly IInterceptor _interceptor;
    public MyServiceClientFactory(IInterceptor interceptor)
    {
        _interceptor = interceptor;
        _proxyGenerator = new ProxyGenerator();
    }
    public IMyService Create()
    {
        IMyService proxy = _proxyGenerator.CreateInterfaceProxyWithTargetInterface<IMyService>(null, _interceptor);
        return proxy;
    }
}

然后我实现了拦截器。在每个方法调用时，将调用此拦截器，它将从提供的IMyService创建一个新的IMyServiceFactory，并将方法调用委托给该新实例。

public class MyServiceClientInterceptor : IInterceptor
{
    readonly IMyServiceFactory _svcFactory;
    public MyServiceClientInterceptor(IMyServiceFactory svcFactory)
    {
        _svcFactory = svcFactory;
    }
    public void Intercept(IInvocation invocation)
    {
        IMyService realService = _svcFactory.Create();
        IChangeProxyTarget changeProxyTarget = invocation as IChangeProxyTarget;
        changeProxyTarget.ChangeInvocationTarget(realService);
        invocation.Proceed();
    }
}

最后，要充分利用这一切：

// Create a service factory (the to-be-decorated class)
IMyServiceFactory myRealServiceFactory = /* ... */;

// Create a factory that will create decorated services
MyServiceClientInterceptor interceptor = 
        new MyServiceClientInterceptor(myRealServiceFactory);
MyDynamicallyDecoratedServiceClientFactory svcFactory =  
        new MyDynamicallyDecoratedServiceClientFactory(interceptor);

// Create a service client
IMyService svc = svcFactory.Create();

// Use it!
svcProxy.A();

如何动态装饰一个类？

1 个答案: