在处理WCF异常的时候,有大概几种方式:
第一种是在配置文件中,将includeExceptionDetailInFaults设置为true
<behavior name="serviceDebuBehavior"><serviceDebug includeExceptionDetailInFaults="true" /></behavior>
但是这种方式会导致敏感信息泄漏的危险,一般我们仅仅在调试的时候才开启该属性,如果已经发布,为了安全,我们一般会设置成false。
第二种方法是自定义错误,通过FaultException直接指定错误信息。
[ServiceBehavior(IncludeExceptionDetailInFaults = true)]
public class CalculatorService : ICalculator
{
throw new FaultException("被除数y不能为零!");
}
但这样我们还必须为WCF的方法里显式的去抛出异常,如果能像.NET一样,在Global里直接捕获全局的异常,并写入log4net日志多好,有没有方法在wcf里如果出现异常,异常日志写入服务器断,同时抛给客户端呢?
要实现这个,需要三步
第一步: 我们需要实现IErrorHandler接口,实现他的两个方法
bool HandleError(Exception error);
void ProvideFault(Exception error, MessageVersion version, ref Message fault);
其中HandleError是true表示终止当前session
在ProvideFault方法里我们可以写我们要抛给客户端的自定义的错误,同时也可以在服务器端写异常日志。
我们实现一个GlobalExceptionHandler ,继承自IErrorHandler,同时在ProvideFault里通过log4net写服务器端日志,如下:
namespace WcfService
{
using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Dispatcher;
/// <summary>
/// GlobalExceptionHandler
/// </summary>
public class GlobalExceptionHandler : IErrorHandler
{
/// <summary>
/// 测试log4net
/// </summary>
private static readonly log4net.ILog log = log4net.LogManager.GetLogger(typeof(GlobalExceptionHandler));
#region IErrorHandler Members
/// <summary>
/// HandleError
/// </summary>
/// <param name="ex">ex</param>
/// <returns>true</returns>
public bool HandleError(Exception ex)
{
return true;
}
/// <summary>
/// ProvideFault
/// </summary>
/// <param name="ex">ex</param>
/// <param name="version">version</param>
/// <param name="msg">msg</param>
public void ProvideFault(Exception ex, MessageVersion version, ref Message msg)
{
//// 写入log4net
log.Error("WCF异常", ex);
var newEx = new FaultException(string.Format("WCF接口出错 {0}", ex.TargetSite.Name));
MessageFault msgFault = newEx.CreateMessageFault();
msg = Message.CreateMessage(version, msgFault, newEx.Action);
}
#endregion
}
}
第二步:现在我们需要创建一个自定义的Service Behaviour Attribute,让WCF知道当WCF任何异常发生的时候,我们通过这个自定义的Attribute来处理。实现这个需要继承IServiceBehavior接口,并在此类的构造函数里,我们获取到错误类型。
一旦ApplyDispatchBehavior行为被调用时,我们通过Activator.CreateInstance创建错误handler,并把这个错误添加到每个channelDispatcher中。
ApplyDispatchBehavior
channelDispatcher中文叫信道分发器,当我们的ServiceHost调用Open方法,WCF就会创建我们的多个信道分发器(ChannelDispatcher),每个ChannelDispatcher都会拥有一个信道监听器(ChannelListener),ChannelListener就有一直在固定的端口监听,等到Message的到来,调用AcceptChannel构建信道形成信道栈,开始对Message的处理。
using System; using System.Collections.ObjectModel; using System.ServiceModel; using System.ServiceModel.Channels; using System.ServiceModel.Description; using System.ServiceModel.Dispatcher; namespace WcfService { public class GlobalExceptionHandlerBehaviourAttribute : Attribute, IServiceBehavior { private readonly Type _errorHandlerType; public GlobalExceptionHandlerBehaviourAttribute(Type errorHandlerType) { _errorHandlerType = errorHandlerType; } #region IServiceBehavior Members public void Validate(ServiceDescription description, ServiceHostBase serviceHostBase) { } public void AddBindingParameters(ServiceDescription description, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection parameters) { } public void ApplyDispatchBehavior(ServiceDescription description, ServiceHostBase serviceHostBase) { var handler = (IErrorHandler) Activator.CreateInstance(_errorHandlerType); foreach (ChannelDispatcherBase dispatcherBase in serviceHostBase.ChannelDispatchers) { var channelDispatcher = dispatcherBase as ChannelDispatcher; if (channelDispatcher != null) channelDispatcher.ErrorHandlers.Add(handler); } } #endregion } }
第三步:在我们的WCF的类上,加上GlobalExceptionHandlerBehaviour
using System; namespace WcfService { [GlobalExceptionHandlerBehaviour(typeof (GlobalExceptionHandler))] public class SomeService : ISomeService { #region ISomeService Members public string SomeFailingOperation() { throw new Exception("Kaboom"); return null; } #endregion } }
这时候,客户端和服务器端都已经分别能记录到错误的异常日志了。
附:log4net配置
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="log4net"
type="log4net.Config.Log4NetConfigurationSectionHandler, log4net, Version=1.2.10.0, Culture=Neutral, PublicKeyToken=bf100aa01a5c2784" />
</configSections>
<log4net>
<!-- 日志文件部分log输出格式的设定 -->
<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="./Logs\Log_" />
<appendToFile value="true" />
<rollingStyle value="Date" />
<datePattern value="yyyyMMdd‘.txt‘" />
<staticLogFileName value="false" />
<layout type="log4net.Layout.PatternLayout">
<header value="------------------------------------------------------------
" />
<ConversionPattern value="%date [%thread] %-5level %logger [%ndc] - %message%newline%newline%newline" />
</layout>
</appender>
<appender name="WcfService.Api_Error" type="log4net.Appender.RollingFileAppender" LEVEL="ERROR">
<file value="./Logs\API\logError_" />
<appendToFile value="true" />
<datePattern value="yyyyMMdd‘.txt‘" />
<rollingStyle value="Date" />
<staticLogFileName value="false" />
<layout type="log4net.Layout.PatternLayout">
<header value="[Header]
" />
<footer value="[Footer]
" />
<conversionPattern value="%date{dd/MM/yyyy-HH:mm:ss} %m%newline%exception" />
</layout>
<filter type="log4net.Filter.LevelRangeFilter">
<param name="LevelMin" value="ERROR" />
<param name="LevelMax" value="ERROR" />
</filter>
</appender>
<appender name="WcfService.Api_Info" type="log4net.Appender.RollingFileAppender" LEVEL="INFO">
<file value="./Logs\API\logInfo_" />
<appendToFile value="true" />
<datePattern value="yyyyMMdd‘.txt‘" />
<rollingStyle value="Date" />
<staticLogFileName value="false" />
<layout type="log4net.Layout.PatternLayout">
<header value="[Header]
" />
<footer value="[Footer]
" />
<conversionPattern value="%date{dd/MM/yyyy-HH:mm:ss} %m%newline%exception" />
</layout>
<filter type="log4net.Filter.LevelRangeFilter">
<param name="LevelMin" value="INFO" />
<param name="LevelMax" value="INFO" />
</filter>
</appender>
<root>
<level value="All" />
<appender-ref ref="RollingLogFileAppender" />
</root>
<logger name="WcfService" additivity="false">
<appender-ref ref="WcfService.Api_Info" />
<appender-ref ref="WcfService.Api_Error" />
</logger>
</log4net>
</configuration>