如何配置使用 Log4j

最近在用Java 写一个FTP上传下载文件工具，正好需要产生操作日志。

利用Log4j.jar可以轻松解决。下面介绍一下Log4j的使用，具体概念到官网查阅：

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1、下载：

http://archive.apache.org/dist/logging/log4j/

2、添加jar到java项目：

3、创建：Log4j.Properties文件，放在src文件夹下即可：

  3.1 输出到console端：

<span style="color:#666666;font-style: italic;"># Root logger option</span>
log4j.rootLogger=INFO, stdout
 
<span style="color:#666666;font-style: italic;"># Direct log messages to stdout</span> 
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=<span style="color:#000000;font-weight: bold;">%</span>d<span style="font-weight: bold;">{</span>yyyy-MM-dd HH:mm:ss<span style="font-weight: bold;">}</span> <span style="color:#000000;font-weight: bold;">%</span>-5p <span style="color:#000000;font-weight: bold;">%</span>c<span style="font-weight: bold;">{</span><span style="color:#000000;">1</span><span style="font-weight: bold;">}</span>:<span style="color:#000000;font-weight: bold;">%</span>L - <span style="color:#000000;font-weight: bold;">%</span>m<span style="color:#000000;font-weight: bold;">%</span>n

   3.2 输出到日志文件：

<span style="color:#666666;font-style: italic;"># Root logger option</span>
log4j.rootLogger=INFO, <span style="font-weight: bold;">file</span>
 
<span style="color:#666666;font-style: italic;"># Direct log messages to a log file</span>
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=C:\loging.log
log4j.appender.file.MaxFileSize=1MB
log4j.appender.file.MaxBackupIndex=<span style="color:#000000;">1</span>
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=<span style="color:#000000;font-weight: bold;">%</span>d<span style="font-weight: bold;">{</span>yyyy-MM-dd HH:mm:ss<span style="font-weight: bold;">}</span> <span style="color:#000000;font-weight: bold;">%</span>-5p <span style="color:#000000;font-weight: bold;">%</span>c<span style="font-weight: bold;">{</span><span style="color:#000000;">1</span><span style="font-weight: bold;">}</span>:<span style="color:#000000;font-weight: bold;">%</span>L - <span style="color:#000000;font-weight: bold;">%</span>m<span style="color:#000000;font-weight: bold;">%</span>n

  3.3 输出到console同时输出到日志文件：

<span style="color:#666666;font-style: italic;"># Root logger option</span>
log4j.rootLogger=INFO, <span style="font-weight: bold;">file</span>, stdout
 
<span style="color:#666666;font-style: italic;"># Direct log messages to a log file</span>
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=C:\loging.log
log4j.appender.file.MaxFileSize=1MB
log4j.appender.file.MaxBackupIndex=<span style="color:#000000;">1</span>
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=<span style="color:#000000;font-weight: bold;">%</span>d<span style="font-weight: bold;">{</span>yyyy-MM-dd HH:mm:ss<span style="font-weight: bold;">}</span> <span style="color:#000000;font-weight: bold;">%</span>-5p <span style="color:#000000;font-weight: bold;">%</span>c<span style="font-weight: bold;">{</span><span style="color:#000000;">1</span><span style="font-weight: bold;">}</span>:<span style="color:#000000;font-weight: bold;">%</span>L - <span style="color:#000000;font-weight: bold;">%</span>m<span style="color:#000000;font-weight: bold;">%</span>n
 
<span style="color:#666666;font-style: italic;"># Direct log messages to stdout</span>
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=<span style="color:#000000;font-weight: bold;">%</span>d<span style="font-weight: bold;">{</span>yyyy-MM-dd HH:mm:ss<span style="font-weight: bold;">}</span> <span style="color:#000000;font-weight: bold;">%</span>-5p <span style="color:#000000;font-weight: bold;">%</span>c<span style="font-weight: bold;">{</span><span style="color:#000000;">1</span><span style="font-weight: bold;">}</span>:<span style="color:#000000;font-weight: bold;">%</span>L - <span style="color:#000000;font-weight: bold;">%</span>m<span style="color:#000000;font-weight: bold;">%</span>n

  3.4  按天roll over（翻滚，转存）日志：

<span style="color:#666666;font-style: italic;"></span># Root logger option
log4j.rootLogger=INFO,console,<span style="background-color: rgb(51, 255, 51);">dailyFile</span>
##Daily log:
log4j.appender.dailyFile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.dailyFile.File=e:/ftplog/autoftp.log
log4j.appender.dailyFile.Append=true
log4j.appender.dailyFile.layout=org.apache.log4j.PatternLayout  
log4j.appender.dailyFile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p - %m%n
log4j.appender.dailyFile.Threshold=INFO
<span style="color:#33ff33;"><span style="background-color: rgb(51, 255, 51);"><span style="color:#000000;">log4j.appender.dailyFile.DatePattern='.'yyyy-MM-dd</span></span> </span> 

# Direct log messages to console
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Threshold=INFO
log4j.appender.console.ImmediateFlush=true
log4j.appender.console.Target=System.out
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

PS：

Debug Level:  日志记录等级

We have used DEBUG with both the appenders. All the possible options are:

• TRACE

• DEBUG

• INFO

• WARN

• ERROR

• FATAL

• ALL

Daily Log File Generation: 每日文件生成模式

DatePattern	Description
'.' yyyy-MM	Roll over at the end of each month and the beginning of the next month.
'.' yyyy-MM-dd	This is the default value and roll over at midnight each day.
'.' yyyy-MM-dd-a	Roll over at midday and midnight of each day.
'.' yyyy-MM-dd-HH	Roll over at the top of every hour.
'.' yyyy-MM-dd-HH-mm	Roll over every minute.
'.' yyyy-ww	Roll over on the first day of each week depending upon the locale.

4、测试代码如下：

import org.apache.log4j.Logger;
    import org.apache.log4j.BasicConfigurator;

    public class Hello {

      static Logger logger = Logger.getLogger(Hello.class);

      public
      static
      void main(String argv[]) {
        BasicConfigurator.configure();
        logger.debug("Hello world.");
        logger.info("What a beatiful day.");
      }
    }

import org.apache.log4j.Logger;
    import org.apache.log4j.BasicConfigurator;
    
    public class Hello {
    
      static Logger logger = Logger.getLogger(Hello.class);
    
      public
      static
      void main(String argv[]) {
    	BasicConfigurator.configure();
    	logger.debug("Hello world.");
    	logger.info("What a beatiful day.");
      }
    }

Output：

2013-12-14 13:02:06 ERROR Hello:12 - Hello world.
2013-12-14 13:02:06 INFO  Hello:13 - What a beatiful day.

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Dylan   presents.