wcf - 在何时何地设置自定义IOperationInvoker？

Question

我正在尝试扩展WCF，以便可以拥有一个RESTful Web服务，在该服务中，对于每个操作，我都对HTTP授权 header 执行验证，该 header 的值用于调用Login()方法。

登录完成后，我希望调用该操作的相应方法，以检查是否引发了安全异常，在这种情况下，我将使用适当的HTTP状态代码以一条自定义的“拒绝访问”消息进行回复。

考虑到这一点，我认为实现一个将IOperationInvoker的实现应用于每个操作的IEndpointBehavior(设置DispatchOperation.Invoker属性)将是一个好主意。

我决定使用Decorator设计模式实现IOperationInvoker。我的实现将在其构造函数中需要另一个IOperationInvoker，方法调用将委派给该IOperationInvoker。

这是我的IOperationInvokerImplementation:

    public class BookSmarTkOperationInvoker : IOperationInvoker{

    private readonly IOperationInvoker invoker;

    public BookSmarTkOperationInvoker(IOperationInvoker decoratee)
    {
        this.invoker = decoratee;
    }

    public object[] AllocateInputs()
    {
        return this.invoker.AllocateInputs();
    }

    public object Invoke(object instance, object[] inputs, out object[] outputs)
    {
        BeforeOperation(); // Where there's code to perform the login using WebOperationContext.Current
        object o = null;
        try
        {
            o = this.invoker.Invoke(instance, inputs, out outputs);
        }
        catch (Exception exception)
        {
            outputs = null;
            return AfterFailedOperation(exception); // Return a custom access denied response
        }

        return o;
    }

    public IAsyncResult InvokeBegin(object instance, object[] inputs, AsyncCallback callback, object state)
    {
        throw new Exception("The operation invoker is not asynchronous.");
    }

    public object InvokeEnd(object instance, out object[] outputs, IAsyncResult result)
    {
        throw new Exception("The operation invoker is not asynchronous.");
    }

    public bool IsSynchronous
    {
        get
        {
            return false;
        }
    }
}

我决定通过扩展我已经需要的行为(WebHttpBehavior)来实现IEndpointBehavior，这样我就只使用一个beavior。这是我写的代码:

public class BookSmarTkEndpointBehavior : WebHttpBehavior
{
    public override void Validate(ServiceEndpoint endpoint)
    {
        base.Validate(endpoint);
    }

    public override void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
    {
        base.AddBindingParameters(endpoint, bindingParameters);
    }

    public override void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        base.ApplyDispatchBehavior(endpoint, endpointDispatcher);

        foreach (DispatchOperation operation in endpointDispatcher.DispatchRuntime.Operations)
        {
            IOperationInvoker defaultInvoker = operation.Invoker;
            IOperationInvoker decoratorInvoker = new BookSmarTkOperationInvoker(defaultInvoker);
            operation.Invoker = decoratorInvoker;

            Console.Write("Before: " + ((object)defaultInvoker ?? "null"));
            Console.WriteLine(" After: " + operation.Invoker);
        }
    }

    public override void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    {
        base.ApplyClientBehavior(endpoint, clientRuntime);
        throw new Exception("The BookSmarTkEndointBehavior cannot be used in client endpoints.");
    }
}

现在这是问题所在:

在IOperationInvoker中仅调用构造函数，其他方法均无效。

装饰对象IOperationInvoker(在装饰器的构造函数中传递的对象)为null。

我猜想也许其他行为的其他一些代码随后会在OperationDispatcher.Invoker设置中设置另一个IOperationInvoker。因此，压倒我的。这将清楚地解释我的情况。

发生了什么事，我该怎么办？

我的服务是自托管的。

如果需要查看它，这是我在system.serviceModel下的app.config文件中拥有的配置。

<services>
  <service name="BookSmarTk.Web.Service.BookSmarTkService">
    <host>
      <baseAddresses>
        <add baseAddress="http://localhost:8080/service"/>
      </baseAddresses>
    </host>
    <endpoint  
      address=""
      behaviorConfiguration="BookSmaTkEndpointBehavior"
      binding="webHttpBinding" 
      bindingConfiguration="BookSmarTkBinding"
      contract="BookSmarTk.Web.Service.BookSmarTkService">
    </endpoint>
  </service>
</services>

<behaviors>
  <serviceBehaviors>
    <behavior name ="BookSmartkServiceBehavior">
      <serviceDebug httpHelpPageEnabled="true" httpHelpPageUrl="/help.htm" includeExceptionDetailInFaults="true" />
    </behavior>
  </serviceBehaviors>
  <endpointBehaviors>
    <behavior name="BookSmaTkEndpointBehavior">
      <!--<webHttp/>-->
      <bookSmarTkEndpointBehavior />
    </behavior>
  </endpointBehaviors>
</behaviors>

<bindings>
  <webHttpBinding>
    <binding name="BookSmarTkBinding">
    </binding>
  </webHttpBinding>
</bindings>

<extensions>
  <behaviorExtensions>
    <add name="bookSmarTkEndpointBehavior" type="BookSmarTk.Web.Service.BookSmarTkEndpointBehaviorElement, BookSmarTk.Web.Service, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null"/>
  </behaviorExtensions>
</extensions>

我阅读了到目前为止，我非常感谢您。真的很感谢你!

Answer 1

不必在ApplyDispatchBehavior()方法上设置调用程序，而必须创建IOperationBehavior实现程序:

 public class MyOperationBehavior: IOperationBehavior
 {
  public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters)
  {
  }

  public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation)
  {
  }

  public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation)
  {
   dispatchOperation.Invoker = new BookSmarTkOperationInvoker(dispatchOperation.Invoker);
  }

  public void Validate(OperationDescription operationDescription)
  {
  }
 }

然后在ApplyDispatchBehavior()处设置该行为:

  public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
  {
    foreach (var operation in endpoint.Contract.Operations) {
      if (operation.Behaviors.Contains(typeof(MyOperationBehavior)))
       continue;

      operation.Behaviors.Add(new MyOperationBehavior());
   }
  }