最近处理一个日志功能，用log4net的配置不能完全满足要求，所以在其基础上简单封装了一下，支持以下功能：

1 零配置

内置默认配置，引用dll后不需要添加或修改任何配置文件也可以使用

2 动态指定文件路径和文件名

我们的需求是按请求来源和功能生成多个独立的日志文件，例如  /app编号/功能编号.txt 的结构，需要根据请求动态指定文件名称

3 按日期和大小自动分割文件，满足其中一个条件即可

来看实现

一、自定义读取配置文件的Appender

为了同时支持零配置和使用配置文件的方式，采用自定义一个用于读取配置项的Appender，初始化Logger时首先读取配置项中的同名Appender，如果存在使用配置参数，如果不存在则使用默认配置。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;namespace Rainstorm.Log4net
{/// <summary>/// http://blog.csdn.net/autfish/// </summary>public class ReadParamAppender : log4net.Appender.AppenderSkeleton{private string _file;public string File{get { return this._file; }set { _file = value; }}private int _maxSizeRollBackups;public int MaxSizeRollBackups{get { return this._maxSizeRollBackups; }set { _maxSizeRollBackups = value; }}private bool _appendToFile = true;public bool AppendToFile{get { return this._appendToFile; }set { _appendToFile = value; }}private string _maximumFileSize;public string MaximumFileSize{get { return this._maximumFileSize; }set { _maximumFileSize = value; }}private string _layoutPattern;public string LayoutPattern{get { return this._layoutPattern; }set { _layoutPattern = value; }}private string _datePattern;public string DatePattern{get { return this._datePattern; }set { _datePattern = value; }}private string _level;public string Level{get { return this._level; }set { _level = value; }}protected override void Append(log4net.Core.LoggingEvent loggingEvent){}}
}

二、动态创建Logger工厂类

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.Concurrent;
using System.Configuration;using log4net;
using log4net.Appender;
using log4net.Core;
using log4net.Layout;
using log4net.Repository;
using log4net.Repository.Hierarchy;[assembly: log4net.Config.XmlConfigurator(Watch = true)]
namespace Rainstorm.Log4net
{/// <summary>/// http://blog.csdn.net/autfish/// </summary>public static class CustomRollingFileLogger{private static readonly ConcurrentDictionary<string, ILog> loggerContainer = new ConcurrentDictionary<string, ILog>();private static readonly Dictionary<string, ReadParamAppender> appenderContainer = new Dictionary<string, ReadParamAppender>();private static object lockObj = new object();//默认配置private const int MAX_SIZE_ROLL_BACKUPS = 20;private const string LAYOUT_PATTERN = "%d [%t] %-5p %c  - %m%n";private const string DATE_PATTERN = "yyyyMMdd\".txt\"";private const string MAXIMUM_FILE_SIZE = "256MB";private const string LEVEL = "debug";//读取配置文件并缓存static CustomRollingFileLogger(){IAppender[] appenders = LogManager.GetRepository().GetAppenders();for (int i = 0; i < appenders.Length; i++){if (appenders[i] is ReadParamAppender){ReadParamAppender appender = (ReadParamAppender)appenders[i];if (appender.MaxSizeRollBackups == 0){appender.MaxSizeRollBackups = MAX_SIZE_ROLL_BACKUPS;}if (appender.Layout != null && appender.Layout is log4net.Layout.PatternLayout){appender.LayoutPattern = ((log4net.Layout.PatternLayout)appender.Layout).ConversionPattern;}if (string.IsNullOrEmpty(appender.LayoutPattern)){appender.LayoutPattern = LAYOUT_PATTERN;}if (string.IsNullOrEmpty(appender.DatePattern)){appender.DatePattern = DATE_PATTERN;}if (string.IsNullOrEmpty(appender.MaximumFileSize)){appender.MaximumFileSize = MAXIMUM_FILE_SIZE;}if (string.IsNullOrEmpty(appender.Level)){appender.Level = LEVEL;}lock(lockObj){appenderContainer[appenders[i].Name] = appender;}}}}public static ILog GetCustomLogger(string loggerName, string category = null, bool additivity = false){return loggerContainer.GetOrAdd(loggerName, delegate(string name){RollingFileAppender newAppender = null;ReadParamAppender appender = null;if (appenderContainer.ContainsKey(loggerName)){appender = appenderContainer[loggerName];newAppender = GetNewFileApender(loggerName, string.IsNullOrEmpty(appender.File) ? GetFile(category, loggerName) : appender.File, appender.MaxSizeRollBackups,appender.AppendToFile, true, appender.MaximumFileSize, RollingFileAppender.RollingMode.Composite, appender.DatePattern, appender.LayoutPattern);}else{newAppender = GetNewFileApender(loggerName, GetFile(category, loggerName), MAX_SIZE_ROLL_BACKUPS, true, true, MAXIMUM_FILE_SIZE, RollingFileAppender.RollingMode.Composite, DATE_PATTERN, LAYOUT_PATTERN);}log4net.Repository.Hierarchy.Hierarchy repository = (log4net.Repository.Hierarchy.Hierarchy)LogManager.GetRepository();Logger logger = repository.LoggerFactory.CreateLogger(repository, loggerName);logger.Hierarchy = repository;logger.Parent = repository.Root;logger.Level = GetLoggerLevel(appender == null ? LEVEL : appender.Level);logger.Additivity = additivity;logger.AddAppender(newAppender);logger.Repository.Configured = true;return new LogImpl(logger);});}//如果没有指定文件路径则在运行路径下建立 Log\{loggerName}.txtprivate static string GetFile(string category, string loggerName){if (string.IsNullOrEmpty(category)){return string.Format(@"Log\{0}.txt", loggerName);}else{return string.Format(@"Log\{0}\{1}.txt", category, loggerName);}}private static Level GetLoggerLevel(string level){if (!string.IsNullOrEmpty(level)){switch (level.ToLower().Trim()){case "debug":return Level.Debug;case "info":return Level.Info;case "warn":return Level.Warn;case "error":return Level.Error;case "fatal":return Level.Fatal;}}return Level.Debug;}private static RollingFileAppender GetNewFileApender(string appenderName, string file, int maxSizeRollBackups, bool appendToFile = true, bool staticLogFileName = false, string maximumFileSize = "5MB", RollingFileAppender.RollingMode rollingMode = RollingFileAppender.RollingMode.Composite, string datePattern = "yyyyMMdd\".txt\"", string layoutPattern = "%d [%t] %-5p %c  - %m%n"){RollingFileAppender appender = new RollingFileAppender{LockingModel = new FileAppender.MinimalLock(),Name = appenderName,File = file,AppendToFile = appendToFile,MaxSizeRollBackups = maxSizeRollBackups,MaximumFileSize = maximumFileSize,StaticLogFileName = staticLogFileName,RollingStyle = rollingMode,DatePattern = datePattern};PatternLayout layout = new PatternLayout(layoutPattern);appender.Layout = layout;layout.ActivateOptions();appender.ActivateOptions();return appender;}}
}

三、使用方法

3.1 零配置

ILog logger = CustomRollingFileLogger.GetCustomLogger("pay", "10001");
logger.Debug("debug message");

将在运行目录下生成 Log\10001\pay.txt

按日期分割日志文件，如果文件超过256M，也进行分割

3.2 使用配置文件

修改App.config/Web.config，添加或修改项

<configSections><section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/></configSections><log4net><appender name="pay" type="Rainstorm.Log4net.ReadParamAppender"><param name="file" value="D:\\log\\pay.txt"/><param name="appendToFile" value="true"/><param name="maxSizeRollBackups" value="100"/><param name="maximumFileSize" value="2MB"/><param name="datePattern" value="yyyyMMdd'.txt'"/><param name="level" value="debug"/><layout type="log4net.Layout.PatternLayout"><conversionPattern value="%d - %m%n"/></layout></appender><root><level value="INFO"/><appender-ref ref="pay"/></root></log4net>

ILog logger = CustomRollingFileLogger.GetCustomLogger("pay");
logger.Debug("debug message");

配置项均为可选项，具体含义如下：

file

文件路径

appendToFile

如果同名文件已存在，是否在文件中追加日志

maxSizeRollBackups

在发生文件分割时，最多保留的历史文件个数

maximumFileSize

设置按文件大小分割的阈值

datePattern

按日期分割时文件重命名规则

level

logger输出等级

layout

日志输出格式