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Asp.net Web Applicatoin实现自定义HttpModule拦截异常处理

 

Asp.net的NamePipe机制给我们提供了很多扩展性. 使用HttpModule我们可能实现的有:

  • 强制站点范围的Cookie策略

  • 集中化监控与日志

  • 编写设置与删除HTTP头

  • 控制response输出,如删除多余空白字符

  • Session管理

  • 认证与受权

 

下面我们来看如何实现自定义异常处理:

 

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   1:    public class ErrorModule:IHttpModule
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   2:      {
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   3:          #region IHttpModule Members
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   4:
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   5:          /// <summary>
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   6:          /// Disposes of the resources (other than memory) used by the module that implements <see cref="T:System.Web.IHttpModule"/>.
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   7:          /// </summary>
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   8:          public void Dispose()
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   9:          {
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  10:              //do nothing
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  11:          }
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  12:
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  13:          /// <summary>
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  14:          /// Initializes a module and prepares it to handle requests.
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  15:          /// </summary>
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  16:          /// <param name="context">An <see cref="T:System.Web.HttpApplication"/> that provides access to the methods, properties, and events common to all application objects within an ASP.NET application</param>
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  17:          public void Init(HttpApplication context)
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  18:          {
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  19:              context.Error += new EventHandler(customcontext_Error);
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  20:          }
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  21:
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  22:          private void customcontext_Error(object sender, EventArgs e)
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  23:          {
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  24:              HttpContext ctx = HttpContext.Current;
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  25:              HttpResponse response = ctx.Response;
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  26:              HttpRequest request = ctx.Request;
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  27:
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  28:              Exception exception = ctx.Server.GetLastError();
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  29:
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  30:              var sboutput = new StringBuilder();
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  31:              sboutput.Append("Querystring:<p/>");
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  32:              //Get out the query string
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  33:              int count = request.QueryString.Count;
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  34:              for (int i = 0; i < count; i++)
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  35:              {
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  36:                  sboutput.AppendFormat("<br/> {0}:-- {1} ", request.QueryString.Keys[i], request.QueryString[i]);
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  37:              }
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  38:              //Get out the form collection info
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  39:              sboutput.Append("<p>-------------------------<p/>Form:<p/>");
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  40:              count = request.Form.Count;
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  41:              for (int i = 0; i < count; i++)
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  42:              {
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  43:                  sboutput.AppendFormat("<br/> {0}:-- {1}  -- <br/>", request.Form.Keys[i], request.Form[i]);
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  44:              }
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  45:              sboutput.Append("<p>-------------------------<p/>ErrorInfo:<p/>");
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  46:              sboutput.AppendFormat(@"Your request could not processed. Please press the back button on your browser and try again.<br/>
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  47:                                 If the problem persists, please contact technical support<p/>
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  48:                                 Information below is for technical support:<p/>
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  49:                                  <p/>URL:{0}<p/>Stacktrace:---<br/>{1}<p/>InnerException:<br/>{2}"
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  50:           , ctx.Request.Url, exception.InnerException.StackTrace, exception.InnerException);
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  51:
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  52:             response.Write(sboutput.ToString());
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  53:
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  54:              // To let the page finish running we clear the error
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  55:              ctx.Server.ClearError();
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  56:          }
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  57:
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  58:          #endregion
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  59:
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  60:      }

 

上面的代码实现了IHttpModule接口, 实现基于HttpApplication.Error事件, 接着我们自定义输出了一些信息,包括Form,QueryString. 最后把原来的Error信息清除了,这样你看到以前那个黄页了. 这个自定义的Module可以用于调试Web应用程序使用.

Web.config中配置:

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<httpModules>
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      <add name="ErrorLoggingModule" type="MyWeb.ErrorModule"/>
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</httpModules>

 

实际开发中,我们可以做的事儿很多,对这些信息记日志,发邮件. 如下, 我们演示使用Enterprise Library 做异常处理并日志记录,部分代码如下:

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   1:          /// <summary>
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   2:          /// Handles the Error event of the EntLibLogging control.
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   3:          /// </summary>
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   4:          /// <param name="sender">The source of the event.</param>
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   5:          /// <param name="e">The <see cref="System.EventArgs"/> instance containing the event data.</param>
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   6:          /// <remarks>author Petter Liu http://wintersun.cnblogs.com</remarks>
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   7:          private void EntLibLogging_Error(object sender, EventArgs e)
1
   8:          {
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   9:              var builder = new ConfigurationSourceBuilder();
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  10:
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  11:              builder.ConfigureInstrumentation()
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  12:                .ForApplicationInstance("MyApp")
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  13:                .EnableLogging()
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  14:               .EnablePerformanceCounters();
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  15:
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  16:              //a single exception handling policy named MyPolicy for exceptions of type ArgumentNullException.
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  17:              //The handler for this exception policy will log the exception to the General category (defined in the Logging Application Block configuration)
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  18:              //as a warning with event ID 9000, wrap the ArgumentNullException with an InvalidOperationException, set the new exception message to MyMessage, and then re-throw the exception.
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  19:              builder.ConfigureExceptionHandling()
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  20:                  .GivenPolicyWithName("MyPolicy")
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  21:                  .ForExceptionType<ArgumentNullException>()
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  22:                  .LogToCategory("Exception")
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  23:                    .WithSeverity(System.Diagnostics.TraceEventType.Warning)
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  24:                    .UsingEventId(9000)
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  25:                  .WrapWith<InvalidOperationException>()
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  26:                    .UsingMessage("MyMessage")
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  27:                   .ThenNotifyRethrow();
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  28:
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  29:              //logging application
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  30:              builder.ConfigureLogging()
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  31:                 .WithOptions
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  32:                 .DoNotRevertImpersonation()
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  33:                 .LogToCategoryNamed("Exception")
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  34:                 .SendTo.FlatFile("Exception Logging File")
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  35:                  .FormatWith(new FormatterBuilder()
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  36:                  .TextFormatterNamed("Text Formatter")
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  37:                 . UsingTemplate("Timestamp: {timestamp}{newline}Message: {message}{newline}Category: {category}{newline}"))
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  38:                  .ToFile("d:\\logs\\ExceptionsLog.log")
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  39:                 .SendTo.RollingFile("Rolling Log files")
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  40:                 .RollAfterSize(1024)
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  41:                 .ToFile("d:\\logs\\Rollinglog.log")
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  42:                 .LogToCategoryNamed("General")
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  43:                 .WithOptions.SetAsDefaultCategory()
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  44:                 .SendTo.SharedListenerNamed("Exception Logging File");
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  45:
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  46:              var configSource = new DictionaryConfigurationSource();
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  47:              builder.UpdateConfigurationWithReplace(configSource);
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  48:              EnterpriseLibraryContainer.Current  = EnterpriseLibraryContainer.CreateDefaultContainer(configSource);
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  49:
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  50:              var ex = HttpContext.Current.Server.GetLastError();
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  51:              var em = EnterpriseLibraryContainer.Current.GetInstance<ExceptionManager>();
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  52:              em.HandleException(ex.InnerException, "MyPolicy");
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  53:          }

 

注意上面的代码, 为了运行代码您需要引用以下程序集

Enterprise Library Share Common Library
Microsoft.Practices.ServiceLocation
Logging Application Block
Exception Handling Application Block
Exception Handling Logging Provider

这里我们使用Fluent API配置, 因此没有配置XML文件. 所以不需要Web.Config中配置任何信息. 代码中有注释. 为了测试我们使用一个PAGE故意Throw 一个ArgumentNullException. 通过Server.GetLastError()获取Exception, 这时由名为MyPolicy策略处理异常. 对于ArgumentNullException把它们记录日志到名为Exception分类中,这个日志文件位于d:\\logs\\
ExceptionLog.log.实际开发你完全按照你的需要来自定义策略.

然后这个日志文件中写出的内容是这样的:

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----------------------------------------Timestamp: 2011-11-12 5:57:08Message: HandlingInstanceID: a99d005d-5f8d-4613-9522-2d60efb089aaAn exception of type 'System.ArgumentNullException' occurred and was caught.----------------------------------------------------------------------------11/12/2011 13:57:08Type : System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089Message : Value cannot be null.Parameter name: Demo errorSource : MyWebHelp link : ParamName : Demo errorData : System.Collections.ListDictionaryInternalTargetSite : Void Page_Load(System.Object, System.EventArgs)Stack Trace :    at MyWeb.About.Page_Load(Object sender, EventArgs e) in H:\My Project\DotNet40\TDD2010\WebHost\MyWeb\About.aspx.cs:line 14   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)   at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)   at System.Web.UI.Control.OnLoad(EventArgs e)   at System.Web.UI.Control.LoadRecursive()   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)Additional Info:MachineName : USERTimeStamp : 2011-11-12 5:57:08FullName : Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35AppDomainName : 3e5cb21e-3-129655510216406250ThreadIdentity : WindowsIdentity : USER\PetterCategory: Exception

由于我们日志模块我们配置还需要写Rollinglog.log文件,内容如下:

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----------------------------------------Exception Warning: 9000 : Timestamp: 2011-11-12 5:57:08Message: HandlingInstanceID: a99d005d-5f8d-4613-9522-2d60efb089aaAn exception of type 'System.ArgumentNullException' occurred and was caught.----------------------------------------------------------------------------11/12/2011 13:57:08Type : System.ArgumentNullException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089Message : Value cannot be null.Parameter name: Demo errorSource : MyWebHelp link : ParamName : Demo errorData : System.Collections.ListDictionaryInternalTargetSite : Void Page_Load(System.Object, System.EventArgs)Stack Trace :    at MyWeb.About.Page_Load(Object sender, EventArgs e) in H:\My Project\DotNet40\TDD2010\WebHost\MyWeb\About.aspx.cs:line 14   at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)   at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)   at System.Web.UI.Control.OnLoad(EventArgs e)   at System.Web.UI.Control.LoadRecursive()   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)Additional Info:MachineName : USERTimeStamp : 2011-11-12 5:57:08FullName : Microsoft.Practices.EnterpriseLibrary.ExceptionHandling, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35AppDomainName : 3e5cb21e-3-129655510216406250ThreadIdentity : WindowsIdentity : USER\PetterCategory: ExceptionPriority: 0EventId: 9000Severity: WarningTitle:Enterprise Library Exception HandlingMachine: USERApp Domain: 3e5cb21e-3-129655510216406250ProcessId: 2444Process Name: C:\Program Files\Common Files\Microsoft Shared\DevServer\10.0\WebDev.WebServer40.exeThread Name: Win32 ThreadId:2748Extended Properties: ----------------------------------------

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你可以看到上面的EventId=9000与我们之前在CODE中配置是相同的.

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2
在开源社区有一个组件<a href="http://code.google.com/p/elmah/" target="_blank"><span style="color:#E3272D;">ELMAH</span></a>(Error Logging Modules and Handlers for ASP.NET),已实现Error处理发邮件,写DB,发送到SNS等功能. 我们随意来看下它的代码:
它就是基于IHttpModule的扩展,下面代码来ELMAH:

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   1:      /// &lt;summary&gt;

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   2:      /// Provides an abstract base class for &lt;see cref="IHttpModule"/&gt; that

1
   3:      /// supports discovery from within partial trust environments.

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   4:      /// &lt;/summary&gt;

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   5:      public abstract class HttpModuleBase : IHttpModule

1
   6:      {

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   7:          void IHttpModule.Init(HttpApplication context)

1
   8:          {

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   9:              if (context == null)

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  10:                  throw new ArgumentNullException("context");

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  11:

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  12:              if (SupportDiscoverability)

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  13:                  HttpModuleRegistry.RegisterInPartialTrust(context, this);

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  14:

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  15:              OnInit(context);

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  16:          }

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  17:

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  18:          void IHttpModule.Dispose()

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  19:          {

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  20:              OnDispose();

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  21:          }

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  22:

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  23:          /// &lt;summary&gt;

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  24:          /// Determines whether the module will be registered for discovery

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  25:          /// in partial trust environments or not.

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  26:          /// &lt;/summary&gt;

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  27:          protected virtual bool SupportDiscoverability

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  28:          {

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  29:              get { return false; }

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  30:          }

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  31:

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  32:          /// &lt;summary&gt;

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  33:          /// Initializes the module and prepares it to handle requests.

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  34:          /// &lt;/summary&gt;

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  35:          protected virtual void OnInit(HttpApplication application) {}

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  36:

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  37:          /// &lt;summary&gt;

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  38:          /// Disposes of the resources (other than memory) used by the module.

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  39:          /// &lt;/summary&gt;

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  40:          protected virtual void OnDispose() {}

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  41:      }

 

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这是ErrorLogModule实现之前HttpModuleBase:

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   1:  public class ErrorLogModule : HttpModuleBase, IExceptionFiltering

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   2:      {

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   3:          public event ExceptionFilterEventHandler Filtering;

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   4:          public event ErrorLoggedEventHandler Logged;

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   5:

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   6:          /// &lt;summary&gt;

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   7:          /// Initializes the module and prepares it to handle requests.

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   8:          /// &lt;/summary&gt;

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   9:

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  10:          protected override void OnInit(HttpApplication application)

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  11:          {

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  12:              if (application == null)

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  13:                  throw new ArgumentNullException("application");

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  14:

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  15:              application.Error += new EventHandler(OnError);

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  16:              ErrorSignal.Get(application).Raised += new ErrorSignalEventHandler(OnErrorSignaled);

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  17:          }

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  18:

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  19:          /// &lt;summary&gt;

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  20:          /// Gets the &lt;see cref="ErrorLog"/&gt; instance to which the module

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  21:          /// will log exceptions.

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  22:          /// &lt;/summary&gt;

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  23:          protected virtual ErrorLog GetErrorLog(HttpContext context)

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  24:          {

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  25:              return ErrorLog.GetDefault(context);

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  26:          }

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  27:

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  28:          /// &lt;summary&gt;

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  29:          /// The handler called when an unhandled exception bubbles up to

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  30:          /// the module.

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  31:          /// &lt;/summary&gt;

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  32:          protected virtual void OnError(object sender, EventArgs args)

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  33:          {

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  34:              HttpApplication application = (HttpApplication) sender;

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  35:              LogException(application.Server.GetLastError(), application.Context);

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  36:          }

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  37:

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  38:          /// &lt;summary&gt;

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  39:          /// The handler called when an exception is explicitly signaled.

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  40:          /// &lt;/summary&gt;

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  41:          protected virtual void OnErrorSignaled(object sender, ErrorSignalEventArgs args)

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  42:          {

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  43:              LogException(args.Exception, args.Context);

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  44:          }

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  45:

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  46:          /// &lt;summary&gt;

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  47:          /// Logs an exception and its context to the error log.

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  48:          /// &lt;/summary&gt;

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  49:          protected virtual void LogException(Exception e, HttpContext context)

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  50:          {

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  51:              if (e == null)

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  52:                  throw new ArgumentNullException("e");

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  53:

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  54:              //

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  55:              // Fire an event to check if listeners want to filter out

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  56:              // logging of the uncaught exception.

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  57:              //

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  58:

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  59:              ExceptionFilterEventArgs args = new ExceptionFilterEventArgs(e, context);

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  60:              OnFiltering(args);

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  61:

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  62:              if (args.Dismissed)

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  63:                  return;

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  64:

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  65:              //

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  66:              // Log away...

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  67:              //

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  68:

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  69:              ErrorLogEntry entry = null;

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  70:

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  71:              try

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  72:              {

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  73:                  Error error = new Error(e, context);

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  74:                  ErrorLog log = GetErrorLog(context);

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  75:                  string id = log.Log(error);

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  76:                  entry = new ErrorLogEntry(log, id, error);

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  77:              }

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  78:              catch (Exception localException)

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  79:              {

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  80:                  //

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  81:                  // IMPORTANT! We swallow any exception raised during the

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  82:                  // logging and send them out to the trace . The idea

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  83:                  // here is that logging of exceptions by itself should not

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  84:                  // be  critical to the overall operation of the application.

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  85:                  // The bad thing is that we catch ANY kind of exception,

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  86:                  // even system ones and potentially let them slip by.

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  87:                  //

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  88:

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  89:                  Trace.WriteLine(localException);

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  90:              }

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  91:

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  92:              if (entry != null)

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  93:                  OnLogged(new ErrorLoggedEventArgs(entry));

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  94:          }

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  95:

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  96:          /// &lt;summary&gt;

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  97:          /// Raises the &lt;see cref="Logged"/&gt; event.

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  98:          /// &lt;/summary&gt;

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  99:          protected virtual void OnLogged(ErrorLoggedEventArgs args)

1
100:          {

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101:              ErrorLoggedEventHandler handler = Logged;

1
102:

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103:              if (handler != null)

1
104:                  handler(this, args);

1
105:          }

1
106:

1
107:          /// &lt;summary&gt;

1
108:          /// Raises the &lt;see cref="Filtering"/&gt; event.

1
109:          /// &lt;/summary&gt;

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110:          protected virtual void OnFiltering(ExceptionFilterEventArgs args)

1
111:          {

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112:              ExceptionFilterEventHandler handler = Filtering;

1
113:

1
114:              if (handler != null)

1
115:                  handler(this, args);

1
116:          }

1
117:

1
118:          /// &lt;summary&gt;

1
119:          /// Determines whether the module will be registered for discovery

1
120:          /// in partial trust environments or not.

1
121:          /// &lt;/summary&gt;

1
122:          protected override bool SupportDiscoverability

1
123:          {

1
124:              get { return true; }

1
125:          }

1
126:      }

 

1
更多的功能等待您去挖掘,我们在实际开发中按需选择.希望这篇POST对您开发有帮助.

转自：http://www.cnblogs.com/wintersun/archive/2011/11/12/2246513.html

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