ASP.NET 系列：單元測試之Log4Net

使用Log組件時，我們通常自定義ILogger接口，使用Log4Net等組件進行適配來定義不同的實現類。使用Log4Net日志組件時，為了即方便單元測試又能使用配置文件，我們通過Log4Net的ILogger接口使用Log4Net，對Log4Net進行單元測試時我們可以通過使用MemoryAppender方式測試。

1.定義ILogger接口

ILogger可以通過使用日志級別的枚舉類型精簡方法數量，也可以不適用枚舉直接定義多個方法。

public interface ILogger
{
    void Debug(string format, params string[] args);


void Error(string format, params string[] args);

void Fatal(string format, params string[] args);

void Info(string format, params string[] args);

void Warn(string format, params string[] args);

}</pre> 
 
2.創建使用Log4Net適配的實現類Log4NetAdapter

public class Log4NetAdapter : ILogger
{
    private readonly ILog _rootLogger;


public Log4NetAdapter(ILog rootLogger)
{
    this._rootLogger = rootLogger;
}

public void Debug(string format, params string[] args)
{
    if (this._rootLogger.IsDebugEnabled)
    {
        _rootLogger.Debug(string.Format(format, args));
    }
}

public void Info(string format, params string[] args)
{
    if (this._rootLogger.IsInfoEnabled)
    {
        _rootLogger.Info(string.Format(format, args));
    }
}

public void Warn(string format, params string[] args)
{
    if (this._rootLogger.IsWarnEnabled)
    {
        _rootLogger.Warn(string.Format(format, args));
    }
}

public void Error(string format, params string[] args)
{
    if (this._rootLogger.IsErrorEnabled)
    {
        _rootLogger.Error(string.Format(format, args));
    }
}

public void Fatal(string format, params string[] args)
{
    if (this._rootLogger.IsFatalEnabled)
    {
        _rootLogger.Fatal(string.Format(format, args));
    }
}

}</pre> 
 
3.使用MemoryAppender進行單元測試

public class Log4netAdapterTest
{
    private MemoryAppender _appender;


[Fact]
public void Test()
{
    _appender = new MemoryAppender
    {
        Name = "Unit Testing Appender",
        Layout = new log4net.Layout.PatternLayout("%message")
    };
    _appender.ActivateOptions();

    var root = ((Hierarchy)log4net.LogManager.GetRepository()).Root;
    root.AddAppender(_appender);
    root.Repository.Configured = true;

    ILogger logger = new Log4NetAdapter(log4net.LogManager.GetLogger("root"));
    logger.Info("test {0}", "message");
    Assert.Equal(_appender.GetEvents()[0].MessageObject.ToString(), string.Format("test {0}", "message"));
}

}</pre> 
 
4.創建Log4NetLoggerFactory

通常我們使用配置文件方式配置Log4Net，因此創建Log4NetLoggerFactory提供從配置文件中創建的ILog對象。
public class LoggerFactory
{
    private static readonly log4net.ILog log = log4net.LogManager.GetLogger(typeof(LoggerFactory));


static LoggerFactory()
{
    log4net.Config.XmlConfigurator.Configure();
}

public static ILogger GetLogger()
{
    return new Log4NetAdapter(log);
}

}</pre> 
 
參考的配置文件

<configSections>
  <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
</configSections>

<log4net>
  <root>
    <level value="ALL" />
    <appender-ref ref="RollingLogFileAppender" />
  </root>
  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <param name="File" value="App_Data/Logs/log.txt" />
    <param name="AppendToFile" value="true" />
    <param name="RollingStyle" value="Date" />
    <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
    <preserveLogFileNameExtension value="true" />
    <datePattern value="yyyyMMdd" />
    <param name="StaticLogFileName" value="false" />
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level %logger [%ndc] - %message%newline" />
    </layout>
  </appender>
</log4net></pre> 
 
4.通過依賴注入使用ILogger

在ASP.NET項目中使用時，通過DI容器進行注入。
protected void Application_Start()
{
    //...
    ObjectFactory.AddSingleton<ILogger, Log4NetAdapter>(LoggerFactory.GetLogger());
    //...
}
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