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浅谈在JAVA项目中LOG4J的使用

投稿:jingxian

下面小编就为大家带来一篇浅谈在JAVA项目中LOG4J的使用。小编觉得挺不错的,现在就分享给大家,也给大家做个参考。一起跟随小编过来看看吧

一、直接使用:

//输出到项目文件夹下output1.txt文件中

//////////////////////////////

// DEBUG - Here is some DEBUG

// INFO - Here is some INFO

// WARN - Here is some WARN

// ERROR - Here is some ERROR

// FATAL - Here is some FATAL

//////////////////////////////

package hunnu.sanha.test;

import org.apache.log4j.Level;

import org.apache.log4j.Logger;

import org.apache.log4j.SimpleLayout;

import org.apache.log4j.FileAppender;

public class Simpandfile {

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

 public static void main(String args[]) {

  SimpleLayout layout = new SimpleLayout();

  FileAppender appender = null;

  try {

   appender = new FileAppender(layout,"output1.txt",false);

  } catch(Exception e) {}

  logger.addAppender(appender);

  logger.setLevel((Level) Level.);

  logger.debug("Here is some DEBUG");

  logger.info("Here is some INFO");

  logger.warn("Here is some WARN");

  logger.error("Here is some ERROR");

  logger.fatal("Here is some FATAL");

 }

}

 

//按格式输出到项目文件夹下output2.html

package hunnu.sanha.test;

import java.io.*;

import org.apache.log4j.Level;

import org.apache.log4j.Logger;

import org.apache.log4j.HTMLLayout;

import org.apache.log4j.WriterAppender;

public class Htmlandwrite {

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

 public static void main(String args[]) {

  HTMLLayout layout = new HTMLLayout();

  WriterAppender appender = null;

  try {

   FileOutputStream output = new FileOutputStream("output2.html");

   appender = new WriterAppender(layout,output);

  } catch(Exception e) {}

  logger.addAppender(appender);

  logger.setLevel((Level) Level.);

  logger.debug("Here is some DEBUG");

  logger.info("Here is some INFO");

  logger.warn("Here is some WARN");

  logger.error("Here is some ERROR");

  logger.fatal("Here is some FATAL");

 }

}

 

 

//输出到控制台

////////////////////////////////////////////////////////////////////////////////////////////////////////////

Milliseconds since program start: 0

Classname of caller: hunnu.sanha.test.Consandpatt

Date in ISO8601 format: 2008-07-29 11:02:30,578

Location of log event: hunnu.sanha.test.Consandpatt.main(Consandpatt.java:20)

Message: Here is some DEBUG

 

Milliseconds since program start: 15

Classname of caller: hunnu.sanha.test.Consandpatt

Date in ISO8601 format: 2008-07-29 11:02:30,593

Location of log event: hunnu.sanha.test.Consandpatt.main(Consandpatt.java:21)

Message: Here is some INFO

 

Milliseconds since program start: 15

Classname of caller: hunnu.sanha.test.Consandpatt

Date in ISO8601 format: 2008-07-29 11:02:30,593

Location of log event: hunnu.sanha.test.Consandpatt.main(Consandpatt.java:22)

Message: Here is some WARN

 

Milliseconds since program start: 15

Classname of caller: hunnu.sanha.test.Consandpatt

Date in ISO8601 format: 2008-07-29 11:02:30,593

Location of log event: hunnu.sanha.test.Consandpatt.main(Consandpatt.java:23)

Message: Here is some ERROR

 

Milliseconds since program start: 15

Classname of caller: hunnu.sanha.test.Consandpatt

Date in ISO8601 format: 2008-07-29 11:02:30,593

Location of log event: hunnu.sanha.test.Consandpatt.main(Consandpatt.java:24)

Message: Here is some FATAL

///////////////////////////////////////////////////////

package hunnu.sanha.test;

import org.apache.log4j.Level;

import org.apache.log4j.Logger;

import org.apache.log4j.PatternLayout;

import org.apache.log4j.ConsoleAppender;

public class Consandpatt {

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

 public static void main(String args[]) {

  // Note, %n is newline

  String pattern = "Milliseconds since program start: %r %n";

    pattern += "Classname of caller: %C %n";

    pattern += "Date in ISO8601 format: %d{ISO8601} %n";

    pattern += "Location of log event: %l %n";

    pattern += "Message: %m %n %n";

  

  PatternLayout layout = new PatternLayout(pattern);

  ConsoleAppender appender = new ConsoleAppender(layout);

  logger.addAppender(appender);

  logger.setLevel((Level) Level.);

  logger.debug("Here is some DEBUG");

  logger.info("Here is some INFO");

  logger.warn("Here is some WARN");

  logger.error("Here is some ERROR");

  logger.fatal("Here is some FATAL");

 }

}

二、使用配置文件(都直接放到项目文件夹下)

//xmllog4jconfig.xml

<?xml version="1.0" encoding="UTF-8" ?>

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

 <appender name="appender" class="org.apache.log4j.FileAppender">

  <param name="File" value="Indentify-Log.txt"/>

  <param name="Append" value="false"/>

  <layout class="org.apache.log4j.PatternLayout">

  <param name="ConversionPattern" value="%d [%t] %p - %m%n"/>

  </layout>

 </appender>

 <root>

  <priority value ="debug"/>

  <appender-ref ref="appender"/>

 </root>

</log4j:configuration>

 

//Externalxmltest.java

 package hunnu.sanha.external;

import org.apache.log4j.Logger;

import org.apache.log4j.xml.DOMConfigurator;

public class Externalxmltest {

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

 public static void main(String args[]) {

  DOMConfigurator.configure("xmllog4jconfig.xml");

  logger.debug("Here is some DEBUG");

  logger.info("Here is some INFO");

  logger.warn("Here is some WARN");

  logger.error("Here is some ERROR");

  logger.fatal("Here is some FATAL");

 }

}

//结果输出到Indentify-Log.txt文件中

2008-07-29 10:48:11,375 [main] DEBUG - Here is some DEBUG

2008-07-29 10:48:11,375 [main] INFO - Here is some INFO

2008-07-29 10:48:11,375 [main] WARN - Here is some WARN

2008-07-29 10:48:11,375 [main] ERROR - Here is some ERROR

2008-07-29 10:48:11,375 [main] FATAL - Here is some FATAL

 

 

// plainlog4jconfig.txt

# initialise root logger with level DEBUG and call it BLAH

log4j.rootLogger=DEBUG, BLAH

# add a ConsoleAppender to the logger BLAH

log4j.appender.BLAH=org.apache.log4j.ConsoleAppender

# set set that layout to be SimpleLayout

log4j.appender.BLAH.layout=org.apache.log4j.SimpleLayout

 

//Externalplaintest.java

package hunnu.sanha.external;

import org.apache.log4j.Logger;

import org.apache.log4j.PropertyConfigurator;

public class Externalplaintest {

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

 public static void main(String args[]) {

  PropertyConfigurator.configure("plainlog4jconfig.txt");

  logger.debug("Here is some DEBUG");

  logger.info("Here is some INFO");

  logger.warn("Here is some WARN");

  logger.error("Here is some ERROR");

  logger.fatal("Here is some FATAL");

 }

}

//结果输出到控制台

DEBUG - Here is some DEBUG

INFO - Here is some INFO

WARN - Here is some WARN

ERROR - Here is some ERROR

FATAL - Here is some FATAL

附加:

2.1.   日志信息的优先级

分为OFF、FATAL、ERROR、WARN、INFO、DEBUG、ALL或者您定义的级别。
Log4j建议只使用四个级别,优先级从高到低分别是ERROR、WARN、INFO、DEBUG。通过在这里定义的级别,您可以控制到应用程序中相应级别的日志信息的开关。
假如在一个级别为q的Logger中发生一个级别为p的日志请求,如果p>=q,那么请求将被启用。这是Log4j的核心原则。
比如在这里定义了INFO级别,则应用程序中所有DEBUG级别的日志信息将不被打印出来;

2.2.   输出源的使用

有选择的能用或者禁用日志请求仅仅是Log4j的一部分功能。Log4j允许日志请求被输出到多个输出源。用Log4j的话说,一个输出源被称做一个Appender。
Appender包括console(控制台), files(文件), GUI components(图形的组件), remote socket servers(socket 服务), JMS(java信息服务), NT Event Loggers(NT的事件日志), and remote UNIX Syslog daemons(远程UNIX的后台日志服务)。它也可以做到异步记录。
一个logger可以设置超过一个的appender。
用addAppender 方法添加一个appender到一个给定的logger。对于一个给定的logger它每个生效的日志请求都被转发到该logger所有的appender上和该logger的父辈logger的appender上。

2.2.1.  ConsoleAppender


如果使用ConsoleAppender,那么log信息将写到Console。效果等同于直接把信息打印到System.out上了。

2.2.2.  FileAppender

使用FileAppender,那么log信息将写到指定的文件中。这应该是比较经常使用到的情况。
相应地,在配置文件中应该指定log输出的文件名。如下配置指定了log文件名为dglog.txt
log4j.appender.A2.File=dglog.txt
注意将A2替换为具体配置中Appender的别名。

2.2.3.  DailyRollingAppender

使用FileAppender可以将log信息输出到文件中,但是如果文件太大了读起来就不方便了。这时就可以使用DailyRollingAppender。DailyRollingAppender可以把Log信息输出到按照日期来区分的文件中。配置文件就会每天产生一个log文件,每个log文件只记录当天的log信息:
log4j.appender.A2=org.apache.log4j.DailyRollingFileAppender
log4j.appender.A2.file=dglog
log4j.appender.A2.DatePattern='.'yyyy-MM-dd
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern= %5r %-5p %c{2} - %m%n

2.2.4.  org.apache.log4j.RollingFileAppender


文件大小到达指定尺寸的时候产生一个新的文件。
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File= ../logs/dglog.log
# Control the maximum log file size
log4j.appender.R.MaxFileSize=100KB
# Archive log files (one backup file here)
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n
这个配置文件指定了输出源R,是一个轮转日志文件。最大的文件是100KB,当一个日志文件达到最大尺寸时,Log4J会自动把example.log重命名为dglog.log.1,然后重建一个新的dglog.log文件,依次轮转。

2.2.5.  org.apache.log4j.WriterAppender

将日志信息以流格式发送到任意指定的地方。

2.3.  Layout的配置

Layout指定了log信息输出的样式。

2.3.1.  布局样式

org.apache.log4j.HTMLLayout(以HTML表格形式布局),
org.apache.log4j.PatternLayout(可以灵活地指定布局模式),
org.apache.log4j.SimpleLayout(包含日志信息的级别和信息字符串),
org.apache.log4j.TTCCLayout(包含日志产生的时间、线程、类别等等信息)

2.3.2.  格式


%m 输出代码中指定的消息
%p 输出优先级,即DEBUG,INFO,WARN,ERROR,FATAL
%r 输出自应用启动到输出该log信息耗费的毫秒数
%c 输出所属的类目,通常就是所在类的全名
%t 输出产生该日志事件的线程名
%n 输出一个回车换行符,Windows平台为"rn",Unix平台为"n"
%d 输出日志时间点的日期或时间,默认格式为ISO8601,也可以在其后指定格式,比如:%d{yyy MMM dd HH:mm:ss,SSS},输出类似:2002年10月18日 22:10:28,921
%l 输出日志事件的发生位置,包括类目名、发生的线程,以及在代码中的行数。举例:Testlog4.main(Test Log4.java:10)

2.3.3.  例子

例子1:显示日期和log信息
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %m%n
打印的信息是:
2002-11-12 11:49:42,866 SELECT * FROM Role WHERE 1=1 order by createDate desc

例子2:显示日期,log发生地方和log信息
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %l "#" %m%n
2002-11-12 11:51:46,313 cn.net.unet.weboa.system.dao.RoleDAO.select(RoleDAO.java:409) "#"
SELECT * FROM Role WHERE 1=1 order by createDate desc 
 
例子3:显示log级别,时间,调用方法,log信息
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS}
method:%l%n%m%n
log信息:
[DEBUG] 2002-11-12 12:00:57,376
method:cn.net.unet.weboa.system.dao.RoleDAO.select(RoleDAO.java:409)
SELECT * FROM Role WHERE 1=1 order by createDate desc

2.4.   配置文件的例子:

log4j.rootLogger=DEBUG
#将DAO层log记录到DAOLog,allLog中
log4j.logger.DAO=DEBUG,A2,A4
#将逻辑层log记录到BusinessLog,allLog中
log4j.logger.Businesslog=DEBUG,A3,A4

#A1--打印到屏幕上
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-5p [%t] %37c %3x - %m%n

#A2--打印到文件DAOLog中--专门为DAO层服务
log4j.appender.A2=org.apache.log4j.DailyRollingFileAppender
log4j.appender.A2.file=DAOLog
log4j.appender.A2.DatePattern='.'yyyy-MM-dd
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS}
method:%l%n%m%n

#A3--打印到文件BusinessLog中--专门记录逻辑处理层服务log信息
log4j.appender.A3=org.apache.log4j.DailyRollingFileAppender
log4j.appender.A3.file=BusinessLog
log4j.appender.A3.DatePattern='.'yyyy-MM-dd
log4j.appender.A3.layout=org.apache.log4j.PatternLayout
log4j.appender.A3.layout.ConversionPattern=[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS}
method:%l%n%m%n

#A4--打印到文件alllog中--记录所有log信息
log4j.appender.A4=org.apache.log4j.DailyRollingFileAppender
log4j.appender.A4.file=alllog
log4j.appender.A4.DatePattern='.'yyyy-MM-dd
log4j.appender.A4.layout=org.apache.log4j.PatternLayout
log4j.appender.A4.layout.ConversionPattern=[%-5p] %d{yyyy-MM-dd HH:mm:ss,SSS}
method:%l%n%m%n

以上这篇浅谈在JAVA项目中LOG4J的使用就是小编分享给大家的全部内容了,希望能给大家一个参考,也希望大家多多支持脚本之家。

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