C# Log4Net学习笔记：记录日志到数据库

    一、数据准备

    在SQL Server中创建记录日志的数据表LogDetail：

CREATE TABLE [dbo].[LogDetail](
    [LogID] [INT] IDENTITY(1,1) NOT NULL, --自增ID
    [LogDate] [DATETIME] NULL,            --日志时间
    [LogLevel] [NVARCHAR](10) NULL,       --日志级别
    [LogThread] [NVARCHAR](10) NULL,      --线程ID
    [Logger] [NVARCHAR](50) NULL,         --日志名称
    [LogMessage] [NVARCHAR](3000) NULL,   --日志内容
 CONSTRAINT [PK_LogDetail] PRIMARY KEY CLUSTERED 
(
    [LogID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

    在此表中，日志时间、日志级别、线程ID、日志名称都是可以通过配置文件从Log4Net库中取值的，需要重点处理的是日志内容字段。

    二、记录日志到数据库

    2.1、配置文件

    添加一个ConfigFile文件夹，然后在其下面新建一个Log4NetToDB.config的配置文件，接着在其属性的复制到输出目录项下选择始终复制。

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>
  <log4net debug="false">
    <!--type：表示用哪种类型记录日志，log4net.Appender.ADONetAppender表示用数据库记录日志。-->
    <appender name="ADONetAppender" type="log4net.Appender.ADONetAppender">
      
      <!--日志缓存写入条数，设置为0时只要有一条就立刻写到数据库。-->
      <bufferSize value="0" />

      <!--数据库连接串-->
      <!--C:WINDOWSMicrosoft.NETFrameworkv4.0.30319Configmachine.config-->
      <connectionType value="System.Data.SqlClient.SqlConnection, System.Data, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" />

      <!--数据库连接字符串-->
      <connectionString value="Server=.;Database=Test;Uid=sa;Pwd=********;" />
      
      <!--数据库脚本-->
      <commandText value="INSERT INTO LogDetail (LogDate,LogLevel,LogThread,Logger,LogMessage) VALUES (@LogDate,@LogLevel,@LogThread,@Logger,@LogMessage)" />
      
      <!--日志时间-->
      <parameter>
        <parameterName value="@LogDate" />
        <dbType value="DateTime" />
        <layout type="log4net.Layout.RawTimeStampLayout" />
      </parameter>

      <!--日志级别-->
      <parameter>
        <parameterName value="@LogLevel" />
        <dbType value="String" />
        <size value="10" />
        <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="%p" />
        </layout>
      </parameter>
      
      <!--线程ID-->
      <parameter>
        <parameterName value="@LogThread" />
        <dbType value="String" />
        <size value="10" />
        <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="%t" />
        </layout>
      </parameter>

      <!--日志名称-->
      <parameter>
        <parameterName value="@Logger" />
        <dbType value="String" />
        <size value="50" />
        <layout type="log4net.Layout.PatternLayout">
          <conversionPattern value="%logger" />
        </layout>
      </parameter>
      
      <!--日志内容-->
      <parameter>
        <parameterName value="@LogMessage" />
        <dbType value="String" />
        <size value="3000" />
        <layout type="LinkTo.Test.ConsoleLog4Net.Utility.CustomLayout">
          <conversionPattern value="%property{LogMessage}" />
        </layout>
      </parameter>
    </appender>

    <root>
      <priority value="ALL" />
      <level value="ALL" />
      <appender-ref ref="ADONetAppender" />
    </root>
  </log4net>
</configuration>

    2.2、日志内容处理过程

    注：日志内容处理涉及的4个类(含帮助类)都是存放在Utility文件夹下。

    从配置的<layout type="LinkTo.Test.ConsoleLog4Net.Utility.CustomLayout">可以看出，日志内容的取值来源于一个自定义的Layout类CustomLayout：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using log4net.Layout;

namespace LinkTo.Test.ConsoleLog4Net.Utility
{
    public class CustomLayout : PatternLayout
    {
        /// <summary>
        /// 构造函数：把需要写入数据库的属性添加进来
        /// </summary>
        public CustomLayout()
        {
            AddConverter("property", typeof(CustomLayoutConverter));
        }
    }
}

    CustomLayout类添加属性时，类型来源于CustomLayoutConverter类：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
using System.Threading.Tasks;
using log4net.Core;
using log4net.Layout.Pattern;

namespace LinkTo.Test.ConsoleLog4Net.Utility
{
    public class CustomLayoutConverter : PatternLayoutConverter
    {
        protected override void Convert(TextWriter writer, LoggingEvent loggingEvent)
        {
            if (Option != null)
            {
                //写入指定键的值
                WriteObject(writer, loggingEvent.Repository, LookupProperty(Option, loggingEvent));
            }
            else
            {
                //Write all the key value pairs
                WriteDictionary(writer, loggingEvent.Repository, loggingEvent.GetProperties());
            }
        }

        /// <summary>
        /// 通过反射获取传入的日志对象的某个属性的值
        /// </summary>
        /// <param name="property"></param>
        /// <param name="loggingEvent"></param>
        /// <returns></returns>
        private object LookupProperty(string property, LoggingEvent loggingEvent)
        {
            object propertyValue = string.Empty;
            PropertyInfo propertyInfo = loggingEvent.MessageObject.GetType().GetProperty(property);
            if (propertyInfo != null)
                propertyValue = propertyInfo.GetValue(loggingEvent.MessageObject, null);
            return propertyValue;
        }


    }
}

    从配置的<conversionPattern value="%property{LogMessage}" />可以看出，日志内容的取值来源于属性LogMessage，而这个LogMessage，统一来源于一个实体类LogContent：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace LinkTo.Test.ConsoleLog4Net.Utility
{
    public class LogContent
    {
        /// <summary>
        /// 日志内容
        /// </summary>
        public string LogMessage { get; set; }

        public LogContent(string logMessage)
        {
            LogMessage = logMessage;
        }
    }
}

    2.3、帮助类

    为了简化写日志的过程，封装了一个简单的帮助类LogHelper：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using log4net;

namespace LinkTo.Test.ConsoleLog4Net.Utility
{
    public class LogHelper
    {
        public static readonly ILog logger = LogManager.GetLogger("LinkTo.Test.ConsoleLog4Net");    //这里的参数不能使用Type类型

        public static void Fatal(LogContent content)
        {
            logger.Fatal(content);
        }

        public static void Error(LogContent content)
        {
            logger.Error(content);
        }

        public static void Warn(LogContent content)
        {
            logger.Warn(content);
        }

        public static void Info(LogContent content)
        {
            logger.Info(content);
        }

        public static void Debug(LogContent content)
        {
            logger.Debug(content);
        }
    }
}

    2.4、测试代码

    class Program
    {
        static void Main(string[] args)
        {
            XmlConfigurator.Configure(new FileInfo(Path.Combine(AppDomain.CurrentDomain.BaseDirectory + "ConfigFile\Log4NetToDB.config")));
            LogHelper.Fatal(new LogContent("This is fatal message."));
            LogHelper.Error(new LogContent("This is error message."));
            LogHelper.Warn(new LogContent("This is warn message."));
            LogHelper.Info(new LogContent("This is info message."));
            LogHelper.Debug(new LogContent("This is debug message."));

            Console.Read();
        }
    }

    2.5、运行结果

    2.6、一点优化

    每次写日志时，都需要进行Log4Net文件配置的话，肯定是没有必要的：

XmlConfigurator.Configure(new FileInfo(Path.Combine(AppDomain.CurrentDomain.BaseDirectory + "ConfigFile\Log4NetToDB.config")));

    可以在项目的PropertiesAssemblyInfo.cs最下面加上下面这一句，进行全局的统一配置：

[assembly: log4net.Config.XmlConfigurator(ConfigFile = "ConfigFile\Log4NetToDB.config")]