如何添加要通过 WCF 中的策略注入记录的自定义上下文数据？

Question

我们都知道将 WCF 与 PIAB 结合起来解决横切问题（例如日志记录、验证、审核等）是完全可以的（请访问 http://msdn.microsoft.com/en-us/magazine/cc136759.aspx）。

但 bog 标准日志调用处理程序仅支持日志的一组有限的“扩展属性”。如果需要记录其他信息（例如：客户端 IP 地址、用户 ID 等）怎么办？

答案（由于 stackoverflow 对低评分会员的奇怪政策，稍后将添加为答案）：

Answer 1

经过多次挖掘后，我想出了这个解决方案，我希望它能让其他有相同查询的人受益。

首先，您需要有一个自定义调用处理程序来包含您想要的日志的所有附加数据。您可以参考entlib源代码并查找LogCallHandler。在 GetLogEntry 私有方法中添加附加数据：

    private TraceLogEntry GetLogEntry(IMethodInvocation input)
    {
        var logEntry = new CustomLogEntry();
        var formatter = new CategoryFormatter(input.MethodBase);
        foreach (string category in categories)
        {
            logEntry.Categories.Add(formatter.FormatCategory(category));
        }

        //slot = Thread.GetNamedDataSlot("PatientId");
        //logEntry.PatientId = Thread.GetData(slot).ToString();
        //logEntry.PatientId = CallContext.GetData("__PatientId").ToString();
        logEntry.AppName = ApplicationContext.Current["AppName"].ToString();
        logEntry.ClientIp = ApplicationContext.Current["ClientIp"].ToString();
        logEntry.UserId = ApplicationContext.Current["UserId"].ToString();
        logEntry.PatientId = ApplicationContext.Current["PatientId"].ToString();
        logEntry.EventId = eventId;
        logEntry.Priority = priority;
        logEntry.Severity = severity;
        logEntry.Title = LogCallHandlerDefaults.Title;

        if (includeParameters)
        {
            Dictionary<string, object> parameters = new Dictionary<string, object>();
            for (int i = 0; i < input.Arguments.Count; ++i)
            {
                parameters[input.Arguments.GetParameterInfo(i).Name] = input.Arguments[i];
            }

            logEntry.ExtendedProperties = parameters;
        }

        if (includeCallStack)
        {
            logEntry.CallStack = Environment.StackTrace;
        }

        logEntry.TypeName = input.Target.GetType().FullName;
        logEntry.MethodName = input.MethodBase.Name;
        return logEntry;
    }

之后，您必须创建基础设施以将上下文数据从客户端传播到服务器。我有一个 CallContext 的包装类来存储上下文数据的字典对象：

[Serializable]
public class ApplicationContext : Dictionary<string, object>
{
    private const string CALL_CONTEXT_KEY = "__Context";
    public const string ContextHeaderLocalName = "__Context";
    public const string ContextHeaderNamespace = "urn:tempuri.org";

    private static void EnsureSerializable(object value)
    {
        if (value == null)
        {
            throw new ArgumentNullException("value");
        }
        if (!value.GetType().IsSerializable)
        {
            throw new ArgumentException(string.Format("The argument of the type \"{0}\" is not serializable!", value.GetType().FullName));
        }
    }

    public new object this[string key]
    {
        get { return base[key]; }
        set
        { EnsureSerializable(value); base[key] = value; }
    }

    public int Counter
    {
        get { return (int)this["__Count"]; }
        set { this["__Count"] = value; }
    }

    public static ApplicationContext Current
    {
        get
        {
            if (CallContext.GetData(CALL_CONTEXT_KEY) == null)
            {
                CallContext.SetData(CALL_CONTEXT_KEY, new ApplicationContext());
            }

            return CallContext.GetData(CALL_CONTEXT_KEY) as ApplicationContext;
        }
        set
        {
            CallContext.SetData(CALL_CONTEXT_KEY, value);
        }
    }
}

在服务客户端上，此上下文将通过实现 IClientMessageInspector 添加到请求消息标头。

public class ClientAuditInfoInspector : IClientMessageInspector
{
    #region Implementation of IClientMessageInspector

    public object BeforeSendRequest(ref Message request, IClientChannel channel)
    {
        var contextHeader = new MessageHeader<ApplicationContext>(ApplicationContext.Current);
        request.Headers.Add(contextHeader.GetUntypedHeader(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace));
        return null;
    }

    public void AfterReceiveReply(ref Message reply, object correlationState)
    {
        if (reply.Headers.FindHeader(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace) < 0) { return; }
        var context = reply.Headers.GetHeader<ApplicationContext>(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace);
        if (context == null) { return; }
        ApplicationContext.Current = context;
    }

    #endregion
}

在服务方面，我有一个 ICallContextInitializer 的自定义实现，用于从传入消息中检索消息标头并将其设置回传出消息：

public class AuditInfoCallContextInitializer : ICallContextInitializer
{
    #region Implementation of ICallContextInitializer
    /// <summary>
    /// Extract context data from message header through local name and namespace,
    /// set the data to ApplicationContext.Current.
    /// </summary>
    /// <param name="instanceContext"></param>
    /// <param name="channel"></param>
    /// <param name="message"></param>
    /// <returns></returns>
    public object BeforeInvoke(InstanceContext instanceContext, IClientChannel channel, Message message)
    {
        var context = message.Headers.GetHeader<ApplicationContext>(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace);
        if (context == null) { return null; }

        ApplicationContext.Current = context;
        return ApplicationContext.Current;

    }

    /// <summary>
    /// Retrieve context from correlationState and store it back to reply message header for client.
    /// </summary>
    /// <param name="correlationState"></param>
    public void AfterInvoke(object correlationState)
    {
        var context = correlationState as ApplicationContext;
        if (context == null)
        {
            return;
        }
        var contextHeader = new MessageHeader<ApplicationContext>(context);
        OperationContext.Current.OutgoingMessageHeaders.Add(contextHeader.GetUntypedHeader(ApplicationContext.ContextHeaderLocalName, ApplicationContext.ContextHeaderNamespace));
        ApplicationContext.Current = null;

    }

    #endregion
}

这本质上是消息标头有效负载的往返行程。在 AfterInvoke 方法中，可以在发送回之前修改消息标头。
最后，我创建了一个端点行为来应用 MessageInspector 和 CallContextInitializer。

public class AuditInfoContextPropagationEndpointBehavior : BehaviorExtensionElement, IEndpointBehavior
{
    #region Overrides of BehaviorExtensionElement

    protected override object CreateBehavior()
    {
        return new AuditInfoContextPropagationEndpointBehavior();
    }

    public override Type BehaviorType
    {
        get { return typeof(AuditInfoContextPropagationEndpointBehavior); }
    }

    #endregion

    #region Implementation of IEndpointBehavior

    public void Validate(ServiceEndpoint endpoint)
    {
        return;
    }

    public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
    {
        return;
    }

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {
        foreach (var operation in endpointDispatcher.DispatchRuntime.Operations)
        {
            operation.CallContextInitializers.Add(new AuditInfoCallContextInitializer());
        }

    }

    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    {
        clientRuntime.MessageInspectors.Add(new ClientAuditInfoInspector());
    }

    #endregion
}

您还可以编写合同行为，通过使用行为属性装饰您的服务/合同来实现相同的目的。

现在，您可以从服务客户端设置所有上下文数据，如下所示：

using (var channelFactory = new ChannelFactory<ICustomerService>("WSHttpBinding_ICustomerService"))
        {
            var client = channelFactory.CreateChannel();
            ApplicationContext.Current["AppName"] = "Test application";
            ApplicationContext.Current["ClientIp"] = @"1.1.0.1";
            ApplicationContext.Current["UserId"] = "foo";
            ApplicationContext.Current["PatientId"] = "bar123";

            Console.WriteLine("Retreiving Customer 1");
            Customer cust = client.GetCustomer("1");
            Console.WriteLine("Retreived Customer, Name: [" + cust.Name + "]");
        }

这也发布在 entlib.codeplex 的讨论板上：http://entlib.codeplex.com/discussions/266963