阅读本文之前,请先阅读:Enterprise Library 2.0 -- Logging Application Block (上)
上一篇中我们介绍了如何去配置Logging Application Block,本文将主要介绍Logging Application Block 的基本操作以及Formatter和Trace Listeners 的自定义方法，首先我们来看如何将一个事件日志写入到一个文本文件中。
假设我们按照上一篇的操作配置了Logging Application Block，那么配置文件中的信息如下：
<loggingConfiguration name="Logging Application Block" tracingEnabled="true" defaultCategory="General" logWarningsWhenNoCategoriesMatch="true"> <listeners> <add fileName="trace.log" header="----------------------------------------" footer="----------------------------------------" formatter="SHY520 Formatter" listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.FlatFileTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" traceOutputOptions="None" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.FlatFileTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" name="SHY520 Listeners" /> <add source="Enterprise Library Logging" formatter="Text Formatter" log="Application" machineName="" listenerDataType="Microsoft.Practices.EnterpriseLibrary.Logging.Configuration.FormattedEventLogTraceListenerData, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" traceOutputOptions="None" type="Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners.FormattedEventLogTraceListener, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" name="Formatted EventLog TraceListener" /> </listeners> <formatters> <add template="Timestamp: {timestamp}
Message: {message}
Category: {category}
Priority: {priority}
EventId: {eventid}
Severity: {severity}
Title:{title}
Machine: {machine}
Application Domain: {appDomain}
Process Id: {processId}
Process Name: {processName}
Win32 Thread Id: {win32ThreadId}
Thread Name: {threadName}
Extended Properties: {dictionary({key} - {value}
)}" type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" name="Text Formatter" /> <add template="Timestamp: {timestamp}
Message: {message}
Category: {category}
Priority: {priority}
EventId: {eventid}
Severity: {severity}
Title:{title}
Machine: {machine}
Application Domain: {appDomain}
Process Id: {processId}
Process Name: {processName}
Win32 Thread Id: {win32ThreadId}
Thread Name: {threadName}
Extended Properties: {dictionary({key} - {value}
)}" type="Microsoft.Practices.EnterpriseLibrary.Logging.Formatters.TextFormatter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" name="SHY520 Formatter" /> </formatters> <logFilters> <add categoryFilterMode="AllowAllExceptDenied" type="Microsoft.Practices.EnterpriseLibrary.Logging.Filters.CategoryFilter, Microsoft.Practices.EnterpriseLibrary.Logging, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null" name="Category Filter" /> </logFilters> <categorySources> <add switchValue="All" name="General"> <listeners> <add name="SHY520 Listeners" /> </listeners> </add> </categorySources> <specialSources> <allEvents switchValue="All" name="All Events" /> <notProcessed switchValue="All" name="Unprocessed Category" /> <errors switchValue="All" name="Logging Errors & Warnings"> <listeners> <add name="Formatted EventLog TraceListener" /> </listeners> </errors> </specialSources> </loggingConfiguration>下面我们来看如何将日志写入到文本文件：
[TestMethod] public void DoLog()
{
//创建一个日志条目 LogEntry log = new LogEntry(); //指定该日志所属类别 log.Categories.Add("General"); //日志标题 log.Title = "SHY520's Tests"; log.Message = "there is log information"; //优先级 log.Priority = 0; Logger.Write(log);
}
上面的代码中，我们为该日志指定所属类别为General,在配置文件中我们可以看到General这个类别使用的Trace Listener是SHY520 Listeners，SHY520 Listeners是一个Flat File Trace Listener，它指定了我们的日志信息输出的地方(trace.log),我用的测试项目，运行测试后，该文件在TestResult/out目录中，如果是一般的Web项目或Consle项目，该文件则在Bin/Debug目录下，下面我们来看一下输出的日志信息：
上图中，我们可以看到我们在程序中记录的一些日志信息，我们还可以记录一些额外的信息，这些信息是键值对应的，在1.0版本中我们用Hashtable,这里我们用的是一个泛型的Dictionary类型，代码如下：
[TestMethod] public void LoggEntry() { LogEntry log = new LogEntry(); //事件ID log.EventId = 2000; //日志优先级 log.Priority = 2; log.Message = "Test LogEntry 2"; //日志类别 ICollection<string> coll = new List<string>(); coll.Add("General"); log.Categories = coll; //添加额外信息 Dictionary<string, object> dic = new Dictionary<string, object>(); dic.Add("name", "SHY520"); dic.Add("sex","男"); dic.Add("age", "22"); log.ExtendedProperties = dic; //写入日志 Logger.Write(log); }
然后运行测试，在TestResult/Out目录下的trace.log文件中就能看到我们在程序中添加的额外信息了。
下面我们来介绍一下过滤器的用法：
实现方法很简单，这里我们假设我们已经按照上一篇文章中的方法配置好了一个Category Filter,在Category Filter中我们可以设置要过滤掉哪种类别的事件日志，具体实现方式有两种，如下：
方法一：
[TestMethod] public void TestFilter1() { LogEntry logEntry = new LogEntry(); logEntry.Priority = 2; logEntry.Categories.Add("General"); //ShouldLog()方法根据Filter配置返回是否需要记录日志 if (Logger.GetFilter<CategoryFilter>().ShouldLog(logEntry.Categories))
{
//TODO:记录日志 Logger.Write(logEntry);
} }方法二:
[TestMethod] public void TestFilter2() { LogEntry logEntry = new LogEntry(); logEntry.Priority = 2; logEntry.Categories.Add("General"); if (Logger.ShouldLog(logEntry)) { Logger.Write(logEntry); } }
关于事件日志的过滤就说到这里，下面我们来看看如何创建一个自定义的Trace Listener,首先我们新建一个类(MyListener),并且继承与CustomTraceListener,同时不要忘了在为这个新建的类加上[ConfigurationElementType(typeof(CustomTraceListenerData))]的Attribute，最后重写基类的三个方法，在每个方法中加入自己需要的逻辑既可。完整的类的代码如下：
using System;using System.Collections.Generic;using System.Text;using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;using Microsoft.Practices.EnterpriseLibrary.Logging.Configuration;using Microsoft.Practices.EnterpriseLibrary.Logging;using Microsoft.Practices.EnterpriseLibrary.Logging.TraceListeners;namespace Enterprise_Library_2{ [ConfigurationElementType(typeof(CustomTraceListenerData))] public class MyListener : CustomTraceListener { public override void TraceData(System.Diagnostics.TraceEventCache eventCache, string source, System.Diagnostics.TraceEventType eventType, int id, object data) { if (data is LogEntry && this.Formatter != null) { this.WriteLine(this.Formatter.Format(data as LogEntry)); } else { this.WriteLine(data.ToString()); } } public override void Write(string message) { //TODO：添加自己所需的逻辑 } public override void WriteLine(string message) { //TODO：添加自己所需的逻辑 } }}
然后我们在配置Trace Listener的时候选择Custom Trace Listener就可以了。
接下来我们来看看如何自定义Formatter,实现的方法和上面类似，首先新建一个类MyFormatter,继承ILogFormatter接口，同时加上[ConfigurationElementType(typeof(CustomFormatterData))]的Attribute,完整的代码如下：
using System;using System.Collections.Generic;using System.Text;using System.Collections.Specialized;using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;using Microsoft.Practices.EnterpriseLibrary.Logging.Configuration;using Microsoft.Practices.EnterpriseLibrary.Logging;using Microsoft.Practices.EnterpriseLibrary.Logging.Formatters;namespace Enterprise_Library_2{ [ConfigurationElementType(typeof(CustomFormatterData))] public class MyFormatter : ILogFormatter { public MyFormatter(NameValueCollection nv) { //注意：构造函数的参数必须是NameValueCollection类型的 } public string Format(LogEntry log) { string result = string.Empty; //TODO:此处添加我们个性化的Formatter逻辑 return result; } }}
到这里，关于Logging Application Block的有关问题已经都简单的介绍了一下，有遗漏错误的地方，请指正，谢谢！
希望对初学者有所帮助,同时也欢迎Enterprise Library学习者一起共同交流经验。
Email : pwei013@163.com