问题描述

我见过两个log4net的扩展，它们声称要在日志文件中创建json，但格式从来不是有效的json，这意味着集合不在数组中，也不是Coma分隔的。我用错了吗？还是没有办法将log4net与json一起使用？

<appender name="SessionFileAppender" type="log4net.Appender.FileAppender">
  <file value="Session.log" />
  <appendToFile value="false" />
  <lockingModel type="log4net.Appender.FileAppender+MinimalLock" />
  <layout type='log4net.Layout.SerializedLayout, log4net.Ext.Json'>
    <decorator type='log4net.Layout.Decorators.StandardTypesDecorator, log4net.Ext.Json' />
    <default />
    <remove value='message' />
    <member value='message:messageobject' />
  </layout>
</appender>

输出为：

{"date":"2017-01-29T13:45:50.7345813-05:00","level":"DEBUG","appname":"MyApp.vshost.exe","logger":"MainWindow","thread":"9","ndc":"(null)","message":"Loading new UI instance"}
{"date":"2017-01-29T13:45:50.7380842-05:00","level":"DEBUG","appname":"MyApp.vshost.exe","logger":"MainWindow","thread":"9","ndc":"(null)","message":"Loading internal localization file"}
{"date":"2017-01-29T13:45:50.7510970-05:00","level":"DEBUG","appname":"MyApp.vshost.exe","logger":"MainWindow","thread":"9","ndc":"(null)","message":"Initializing UI"}

这很接近，但不是真正有效的json。

推荐答案

解决方案很简单，我编写了自己的Appender将数据存储在集合中，然后根据需要使用Json.net序列化该集合。这也让我能够在应用程序中查看日志并绑定到它，这也增加了额外的好处。

public class CollectionAppender : AppenderSkeleton
{
    public static ObservableCollection<LogItem> logData = new ObservableCollection<LogItem>();
    protected override void Append(LoggingEvent loggingEvent)
    {
        logData.Add(new LogItem(loggingEvent));
    }
}

public class LogItem
{
    public string Logger { get; private set; }
    public string Level { get; private set; }
    public string Message { get; private set; }
    public DateTime Timestamp { get; private set; }
    public Exception ExceptionData { get; private set; }

    public bool ShouldSerializeExceptionData() //This keeps things tidy when using Json.net for non exemption entries.
    {
        return ExceptionData != null;
    }

    public LogItem(LoggingEvent data)
    {
        Logger = data.LoggerName;
        Level = data.Level.DisplayName;
        Message = data.RenderedMessage;
        Timestamp = data.TimeStamp;
        ExceptionData = data.ExceptionObject;
    }
}

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