如何在WCF服務中使用IDispatchMessageInspector？

Question

我試圖在WCF服務實現中使用IDispatchMessageInspector來訪問自定義標頭值。

就像是：

public class MyService : IMyService
{
    public List<string> GetNames()
    {
        var headerInspector = new CustomHeaderInspector();

        // Where do request & client channel come from?
        var values = headerInspector.AfterReceiveRequest(ref request, clientChannel, OperationContext.Current.InstanceContext);            
    }
}

我已經實現了自己的IDispatchMessageInspector類。

public class CustomHeaderInspector : IDispatchMessageInspector
{
    public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
    {
        var prop = (HttpRequestMessageProperty)request.Properties[HttpRequestMessageProperty.Name];
        var userName = prop.Headers["Username"];

        return userName;
    }
}

我怎么通過

• System.ServiceModel.Channels。 消息和

• System.ServiceModel。 IClientChannel

從服務實現調用AfterReceiveRequest ？

編輯：

許多像這樣或者這樣的文章給出了如何實現自己的ServiceBehavior示例。 所以你的服務實現如下：

[MyCustomBehavior]
public class MyService : IMyService
{
    public List<string> GetNames()
    {
        // Can you use 'MyCustomBehavior' here to access the header properties?
    }
}

因此，我可以在服務操作方法中以某種方式訪問MyCustomBehavior以訪問自定義標頭值嗎？

Answer 1

你必須配置

<extensions>
  <behaviorExtensions>
    <add 
      name="serviceInterceptors" 
      type="CustomHeaderInspector , MyDLL, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null"
    />
  </behaviorExtensions>
</extensions>

然后，擴展將在您的WCF堆棧中處理。 服務本身沒有serviceInterceptors概念，你不必像在第一個代碼塊中那樣做。 WCF堆棧將為您注入Inspector。

MSDN：system.servicemodel.dispatcher.idispatchmessageinspector

Answer 2

我正在使用IClientMessageInspector達到同樣的目標。 以下是如何從代碼中應用它們：

 var serviceClient = new ServiceClientClass(binding, endpointAddress);
serviceClient.Endpoint.Behaviors.Add(
            new MessageInspectorEndpointBehavior<YourMessageInspectorType>());


/// <summary>
/// Represents a run-time behavior extension for a client endpoint.
/// </summary>
public class MessageInspectorEndpointBehavior<T> : IEndpointBehavior
    where T: IClientMessageInspector, new()
{
    /// <summary>
    /// Implements a modification or extension of the client across an endpoint.
    /// </summary>
    /// <param name="endpoint">The endpoint that is to be customized.</param>
    /// <param name="clientRuntime">The client runtime to be customized.</param>
    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    {
        clientRuntime.MessageInspectors.Add(new T());
    }

    /// <summary>
    /// Implement to pass data at runtime to bindings to support custom behavior.
    /// </summary>
    /// <param name="endpoint">The endpoint to modify.</param>
    /// <param name="bindingParameters">The objects that binding elements require to support the behavior.</param>
    public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
    {
        // Nothing special here
    }

    /// <summary>
    /// Implements a modification or extension of the service across an endpoint.
    /// </summary>
    /// <param name="endpoint">The endpoint that exposes the contract.</param>
    /// <param name="endpointDispatcher">The endpoint dispatcher to be modified or extended.</param>
    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        // Nothing special here
    }

    /// <summary>
    /// Implement to confirm that the endpoint meets some intended criteria.
    /// </summary>
    /// <param name="endpoint">The endpoint to validate.</param>
    public void Validate(ServiceEndpoint endpoint)
    {
        // Nothing special here
    }
}

這里是MessageInspector的示例實現，我用它將客戶端版本傳遞給服務器，並在自定義頭文件中檢索服務器版本：

/// <summary>
/// Represents a message inspector object that can be added to the <c>MessageInspectors</c> collection to view or modify messages.
/// </summary>
public class VersionCheckMessageInspector : IClientMessageInspector
{
    /// <summary>
    /// Enables inspection or modification of a message before a request message is sent to a service.
    /// </summary>
    /// <param name="request">The message to be sent to the service.</param>
    /// <param name="channel">The WCF client object channel.</param>
    /// <returns>
    /// The object that is returned as the <paramref name="correlationState " /> argument of
    /// the <see cref="M:System.ServiceModel.Dispatcher.IClientMessageInspector.AfterReceiveReply(System.ServiceModel.Channels.Message@,System.Object)" /> method.
    /// This is null if no correlation state is used.The best practice is to make this a <see cref="T:System.Guid" /> to ensure that no two
    /// <paramref name="correlationState" /> objects are the same.
    /// </returns>
    public object BeforeSendRequest(ref Message request, IClientChannel channel)
    {
        request.Headers.Add(new VersionMessageHeader());
        return null;
    }

    /// <summary>
    /// Enables inspection or modification of a message after a reply message is received but prior to passing it back to the client application.
    /// </summary>
    /// <param name="reply">The message to be transformed into types and handed back to the client application.</param>
    /// <param name="correlationState">Correlation state data.</param>
    public void AfterReceiveReply(ref Message reply, object correlationState)
    {
        var serverVersion = string.Empty;
        var idx = reply.Headers.FindHeader(VersionMessageHeader.HeaderName, VersionMessageHeader.HeaderNamespace);
        if (idx >= 0)
        {
            var versionReader = reply.Headers.GetReaderAtHeader(idx);
            while (versionReader.Name != "ServerVersion"
                   && versionReader.Read())
            {
                serverVersion = versionReader.ReadInnerXml();
                break;
            }
        }

        ValidateServerVersion(serverVersion);
    }

    private static void ValidateServerVersion(string serverVersion)
    {
        // TODO...
    }
}

public class VersionMessageHeader : MessageHeader
{
    public const string HeaderName = "VersionSoapHeader";
    public const string HeaderNamespace = "<your namespace>";
    private const string VersionElementName = "ClientVersion";

    public override string Name
    {
        get { return HeaderName; }
    }

    public override string Namespace
    {
        get { return HeaderNamespace; }
    }

    protected override void OnWriteHeaderContents(XmlDictionaryWriter writer, MessageVersion messageVersion)
    {
        writer.WriteElementString(
            VersionElementName,
            Assembly.GetExecutingAssembly().GetName().Version.ToString());
    }
}

Answer 3

我相信您不需要實現自定義IDispatchMessageInspector來檢索自定義標頭，它可以通過以下服務操作方法完成：

var mp = OperationContext.Current.IncomingMessageProperties;
var property = (HttpRequestMessageProperty)mp[HttpRequestMessageProperty.Name];
var userName = property.Headers["Username"];

如果要中止消息處理，則實現自定義調度消息檢查器是有意義的，例如，如果缺少憑據 - 在這種情況下您可以拋出FaultException。

但是如果你仍然希望將值從調度消息檢查器傳遞給服務操作方法 - 可能它可以通過一些單例與調用標識符（會話標識）一起傳遞，稍后通過方法或使用wcf擴展來提取

Answer 4

我做了什么來訪問我在IDispatchMessageInspector.AfterReceiveRequest設置以下內容的詳細信息

Thread.CurrentPrincipal = new GenericPrincipal(new GenericIdentity(username, "Membership Provider"), roles);

我已經省略了這個驗證碼。

要從服務方法訪問值，您可以調用

Thread.CurrentPrincipal.Identity.Name

Answer 5

在您鏈接到的MSDN頁面上，還有一個描述如何插入檢查器的說明以及一個示例。 報價：

通常，消息檢查器由服務行為，端點行為或合同行為插入。 然后，該行為將消息檢查器添加到DispatchRuntime.MessageInspectors集合。

稍后您將獲得以下示例：

• 實現自定義IDispatchMessageInspector
• 實現將檢查器添加到運行時的自定義IServiceBehavior。
• 通過.config文件配置行為。

這應該足以讓你開始。 否則隨便問:)

如果您只想從服務中訪問標頭，可以嘗試OperationContext.Current.IncomingMessageHeaders 。