问题
在使用WCF的过程中，有时候需要在service端截取client和service之间的消息来做一些如写log，检查message是否合法的操作。 那么如何才能实现呢？
解决方案
使用WCF提供的Inspector功能。我们可以通过实现WCF提供的IParameterInspector或者IDispatchMessageInspector 接口来实现上述需求。以下是需要实现步骤：
1. 实现IParameterInspector或者IDispatchMessageInspector接口
2. 实现IServiceBehavior/IEndpointBehavior/IOperationBehavior接口并把步骤1中实现的Inspector加入到WCF的Message dispatch runtime中
3. 通过Attribute或者配置文件把步骤2中的Behavior应用到WCF service上
接下来我们看看每一步如何实践：
- 步骤一 --- 实现IParameterInspector或者IDispatchMessageInspector接口
实现IParameterInspector的类
public class LogParameterInspector : IParameterInspector
{
public void AfterCall(string operationName, object[] outputs, object returnValue, object correlationState)
{
}
public object BeforeCall(string operationName, object[] inputs)
{
var cinfo = new LogInfo();
cinfo.Action = operationName;
cinfo.StartTimeStamp = DateTime.Now;
cinfo.ServiceName = OperationContext.Current.InstanceContext.GetServiceInstance().GetType().Name;
return cinfo;
}
}
实现IDispatchMessageInspector的类
{
public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
{
LogInfo cinfo = new LogInfo();
//Collect any info that passed in the headers from Client, if any.
cinfo.ServerTimeStamp = DateTime.Now; //Timestamp after the call is received.
cinfo.Platform = "WCF";
OperationDescription operationDesc = GetOperationDescription(OperationContext.Current);
if (operationDesc != null)
{
Type contractType = operationDesc.DeclaringContract.ContractType;
cinfo.Action = operationDesc.Name;
cinfo.ServiceName = contractType.FullName;
cinfo.AssemblyName = contractType.Assembly.GetName().Name;
}
cinfo.ServerName = Dns.GetHostName();
cinfo.ServerProcessName = System.AppDomain.CurrentDomain.FriendlyName;
return cinfo;
}
public void BeforeSendReply(ref Message reply, object correlationState)
{
//correlationState is of type ClientInformation and it is set in AfterReceiveRequest event.
if (correlationState != null)
{
LogInfo cinfo = correlationState as LogInfo;
if (cinfo != null)
{
cinfo.EndTimeStamp = DateTime.Now;
//It's okay to read the RequestMessage since the operation
//has been completed and message is serialized from stream
//(....stream...).
//RequestMessage on OperationContext is short lived.
//It would be too late to serialize the RequestMessage
//in another thread (exception raised: Message is closed)
cinfo.Request = OperationContext.Current.RequestContext.RequestMessage.ToString();
//Message can be read only once.
//Create a BufferedCopy of the Message and be sure to set
//the original message set to a value wich has not been
//copied nor read.
MessageBuffer mb = reply.CreateBufferedCopy(int.MaxValue);
Message responseMsg = mb.CreateMessage();
reply = mb.CreateMessage();
var reader = responseMsg.GetReaderAtBodyContents();
var xodc = new XmlDocument();
xodc.LoadXml(reader.ReadOuterXml());
var oo = reader.ReadContentAsObject();
cinfo.Response = responseMsg.ToString();
if (reply.IsFault == true)
{
cinfo.IsError = true;
}
//Log cinfo async here;
var serialzer = new XmlSerializer(cinfo.GetType());
var writer = new StringWriter();
serialzer.Serialize(writer, cinfo);
File.WriteAllText(@"c:log.xml", writer.ToString());
}
}
}
private OperationDescription GetOperationDescription(OperationContext operationContext)
{
OperationDescription od = null;
string bindingName = operationContext.EndpointDispatcher.ChannelDispatcher.BindingName;
string methodName;
if (bindingName.Contains("WebHttpBinding"))
{
//REST request
methodName = (string)operationContext.IncomingMessageProperties["HttpOperationName"];
}
else
{
//SOAP request
string action = operationContext.IncomingMessageHeaders.Action;
methodName = operationContext.EndpointDispatcher.DispatchRuntime.Operations.FirstOrDefault(o => o.Action == action).Name;
}
EndpointAddress epa = operationContext.EndpointDispatcher.EndpointAddress;
ServiceDescription hostDesc = operationContext.Host.Description;
ServiceEndpoint ep = hostDesc.Endpoints.Find(epa.Uri);
if (ep != null)
{
od = ep.Contract.Operations.Find(methodName);
}
return od;
}
}
- 步骤二 --- 实现IServiceBehavior或者IEndpointBehavior或者IOperationBehavior接口中的一个，以下以实现IServiceBehavior接口为例
实现IServiceBehavior的类
public class ServiceBehavior : Attribute, IServiceBehavior
{
public ServiceBehavior()
{
}
public void AddBindingParameters(
ServiceDescription serviceDescription,
ServiceHostBase serviceHostBase,
Collection<ServiceEndpoint> endpoints,
BindingParameterCollection bindingParameters)
{
}
public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
{
foreach (ChannelDispatcherBase cdb in serviceHostBase.ChannelDispatchers)
{
ChannelDispatcher cd = cdb as ChannelDispatcher;
if (cd != null)
{
foreach (EndpointDispatcher ed in cd.Endpoints)
{
if (!ed.DispatchRuntime.MessageInspectors.Any(inspector => inspector is LogDispatchMessageInspector))
{
ed.DispatchRuntime.MessageInspectors.Add(new LogDispatchMessageInspector());
}
foreach (DispatchOperation op in ed.DispatchRuntime.Operations)
{
if (!op.ParameterInspectors.Any(inspector => inspector is LogParameterInspector))
{
op.ParameterInspectors.Add(new LogParameterInspector());
}
}
}
}
}
}
public void Validate(ServiceDescription serviceDescription, System.ServiceModel.ServiceHostBase serviceHostBase)
{
}
}
- 步骤三 --- 通过Attribute或者配置文件把步骤2中的Behavior应用到WCF service上
我们有如下两种方式把步骤二中实现的Behavior应用到具体的Service上：
1) 让Behavior类继承Attribute，然后把Behavior作为Attribute应用到具体的Service上，如前所示，步骤二中的Behavior已经继承Attribute了，
所以我们可以像下面这样把它应用到具体的service上：
[LogInspector.ServiceBehavior]
public class Service1 : IService1
2) 通过配置文件
编写ServiceBehaviorExtensionElement并继承自BehaviorExtensionElement class，代码如下：
public class ServiceBehaviorExtensionElement : BehaviorExtensionElement
{
protected override object CreateBehavior()
{
return new ServiceBehavior();
}
public override Type BehaviorType
{
get { return typeof(ServiceBehavior); }
}
}
然后在web.config文件中做如下配置：
<system.serviceModel>
<extensions>
<behaviorExtensions>
<add name="LogInspectorExtension" type="LogInspector.ServiceBehaviorExtensionElement, LogInspector"/>
</behaviorExtensions>
</extensions>
<behaviors>
<serviceBehaviors>
<behavior name="LogInpsectorBehavior">
<LogInspectorExtension></LogInspectorExtension>
<!-- To avoid disclosing metadata information, set the values below to false before deployment -->
<serviceMetadata httpGetEnabled="true" httpsGetEnabled="true"/>
<!-- To receive exception details in faults for debugging purposes, set the value below to true. Set to false before deployment to avoid disclosing exception information -->
<serviceDebug includeExceptionDetailInFaults="false"/>
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service name="LogService.Service1" behaviorConfiguration="LogInpsectorBehavior">
<endpoint address="" contract="LogService.IService1" binding="wsHttpBinding"></endpoint>
</service>
</services>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />
</system.serviceModel>
本文代码下载地址：https://github.com/DerekLoveCC/WCF.git
https://blogs.msdn.microsoft.com/carlosfigueira/2011/04/18/wcf-extensibility-message-inspectors/
https://code.msdn.microsoft.com/Generic-WCF-Message-bdf4fb1f