Log4j log4j.xml Example

April 8, 2013 by Lokesh Gupta

Log4j is a simple and flexible logging framework. Logging equips the developer with detailed context for application failures. With log4j it is possible to enable logging at runtime without modifying the application binary. The log4j package is designed so that these statements can remain in shipped code without incurring a heavy performance cost.

Two most common configuration options are in practice industry wide i.e. using log4j.xml configuration and using log4j.properties configuration.

In previous post, we learned about configuring log4j using properties file. This this post, I am showing the example code for log4j.xml configuration.

Step 1) Log4j Maven Dependencies

Create a maven java project and update log4j dependencies.

<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>

Step 2) Create log4j.xml file

This is the main configuration file having all runtime configuration used by log4j. This file will have appenders information, log level information and output file names for file appenders.

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

  <appender name="console" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>

  <appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="demoApplication.log"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>

  <root>
    <priority value ="debug"></priority>
    <appender-ref ref="console"></appender>
    <appender-ref ref="fileAppender"></appender>
  </root>

</log4j:configuration>

Step 3) Configure log4j.xml and test the application

package com.howtodoinjava;

import org.apache.log4j.Logger;
import org.apache.log4j.xml.DOMConfigurator;

public class Log4jXmlConfigurationExample
{
	static Logger logger = Logger.getLogger(Log4jXmlConfigurationExample.class);

	public static void main(String[] args)
	{
		//DOMConfigurator is used to configure logger from xml configuration file
		DOMConfigurator.configure("log4j.xml");

		//Log in console in and log file
		logger.debug("Log4j appender configuration is successful !!");
	}
}

Output in console and demoApplication.log in project root folder:


[main] DEBUG com.howtodoinjava.Log4jXmlConfigurationExample - Log4j xml configuration is successful !!

Now let’s see some log4j.xml examples to output log messages to specific location.

Log4j Console Appender

Output logs to console

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

  <appender name="console" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>

  <root>
    <priority value ="debug"></priority>
    <appender-ref ref="console"></appender>
  </root>

</log4j:configuration>

Log4j Rolling File Appender

Output logs to file

<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>

  <appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="demoApplication.log"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>

  <root>
    <priority value ="debug"></priority>
    <appender-ref ref="fileAppender"></appender>
  </root>

</log4j:configuration>

Let me know if any question.

Happy Learning !!

About Lokesh Gupta

Founded HowToDoInJava.com in late 2012. I love computers, programming and solving problems everyday. A family guy with fun loving nature. You can find me on Facebook, Twitter and Google Plus.

Feedback, Discussion and Comments

bajirao gharage
June 28, 2018
Hi Sir,
Actually we want to dynamic value from java code to print on every line of log file.
Reply
Wasim
March 16, 2017
Hi,
Thanks for sharing this.
How can I log all console output to a file ?
Console output like all the system output i.e system.out.print,system.err.print and all jvm related error/exceptions.
Could you please help me here.
Thanks,
Wasim
Reply
- Lokesh Gupta
  March 16, 2017
```
String fileName = "c:/temp/info.log";

System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream(fileName))));
System.setErr(new PrintStream(new BufferedOutputStream(new FileOutputStream(fileName))));
```
  After you run above code, all output will go to file.
  Reply

Paulo Tavares

January 6, 2017

Hi Lokesh!

I’m new to log4j config. What I’m trying to do is add server name/hostname to the file name of the appender.
Indeed I have the same EAR deployed into 2 different servers (a cluster) using Weblogic and I need server name/hostname to be replaced by the name of each server during start up of the app.
I hope I’ve made myself clear.
Can you help here?
Here is the code:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="true" threshold="debug">

    <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%-4r %-5p [%t] %37c %3x - %m%n"/>
        </layout>
    </appender>

    <appender name="DFe" class="org.apache.log4j.RollingFileAppender">
        <param name="File" value="servers/${weblogic.Name}/logs/dfe_${HERE I WANT TO ADD SERVER NAME/HOSTNAME}.log"/>
        <param name="Append" value="true"/>
        <param name="MaxFileSize" value="10000KB"/>
        <param name="MaxBackupIndex" value="10"/>

        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%X{version} - %d %-5p [%c] %m%n"/>
        </layout>
    </appender>

    <logger name="br.com.synchro.dfe" additivity="false">
        <level value="debug"/>
        <appender-ref ref="DFe"/>
    </logger>

    <root>
        <priority value="error"/>
        <appender-ref ref="DFe"/>
    </root>
</log4j:configuration>

Thanks in advance.
Paulo

Lokesh Gupta
January 6, 2017
You will need to pass hostnames at server startup parameters (usually using -D<paramaName>=<paramValue> format.)
Reply

Ram

October 7, 2016

I am seeing org.xml.sax.SAXParseException; systemId: file:/E:/Fresh%20Start/Practise%20Concepts%20Advanced/log4j-config.xml; lineNumber: 20; columnNumber: 35; The element type “appender-ref” must be terminated by the matching end-tag “”.
at org.apache.xerces.parsers.DOMParser.parse(Unknown Source)
at org.apache.xerces.jaxp.DocumentBuilderImpl.parse(Unknown Source)
at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:205)
at org.apache.log4j.xml.DOMConfigurator$1.parse(DOMConfigurator.java:749)
at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:871)
at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:755)
at org.apache.log4j.xml.DOMConfigurator.configure(DOMConfigurator.java:896)
at log4jdemo.Log4jFromXML.main(Log4jFromXML.java:13)

And my xml file looks like


<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="true" xmlns:log4j='http://jakarta.apache.org/log4j/'>
 
  <appender name="console" class="org.apache.log4j.ConsoleAppender">
    <param name="Target" value="System.out"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>
 
  <appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
    <param name="File" value="demoApplication.log"/>
    <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n" />
    </layout>
  </appender>
 
  <root>
    <priority value ="debug"></priority>
    <appender-ref ref="console"></appender>
    <appender-ref ref="fileAppender"></appender>
  </root>
 
</log4j:configuration>

As same as given above. Please tell me what shall i do ?

Lokesh Gupta

October 7, 2016

<appender-ref ref="console"></appender-ref>
<appender-ref ref="console"></appender-ref>

Orlando
December 3, 2015
Hi,
there is a possibility of a load a parameter file within properties the log4j.xml . I am using WebLogic Server within the server and have the search.properties file within the file and have routAux = / my / dir / out / so that in the log4j.xml can do something like this
within the log4j.xml x. I am using WebLogic Server within the server and have the search.properties arhivo within the file and have routAux = / my / dir / out / so that in the log4j.xml can do something like this
Reply
- Lokesh Gupta
  December 4, 2015
  Looks like code you posted is lost.. Please paste the code inside [xml] … [/xml] tags.
  Reply
Vaibhav
December 1, 2014
HI,
Thanks for posting this.
I am new to the log4j configuration. The problem I am facing is, while printing the loggers on the server log I am getting %3D, %2C type of character instead of = & , characters & so on.
I tried to put , but still problem is remaining as it is.
Can you please guide me how to resolve this issue.
When I searched on google, I came to know It’s encoding issue.
Please suggest.
Thanks,
Reply

Praful

May 13, 2014

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd" >
<log4j:configuration>

<appender name="file" class="org.apache.log4j.RollingFileAppender">
		<param name="maxFileSize" value="10MB" />
		<param name="maxBackupIndex" value="500000" />

		<param name="File" value="C:/LOGS/test.log" />
		<param name="threshold" value="info" />
		<layout class="org.apache.log4j.PatternLayout">
			<param name="ConversionPattern" value="%d %5p %c{1}:%L - %m%n" />
		</layout>
	</appender>

<root>
		<priority value="debug"></priority>
		<appender-ref ref="errorfile" />
		<appender-ref ref="debugfile" />
		<appender-ref ref="file" />
	</root>


</log4j:configuration>

Lokesh

May 13, 2014

You can use <param name="Append" value="true" />

If want to backup file as well then you can use RollingFileAppender with TimeBasedRollingPolicy.

<log4j:configuration debug="true">
  <appender name="ROLL" class="org.apache.log4j.rolling.RollingFileAppender">
    <rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">
      <param name="FileNamePattern" value="/wombat/foo.%d{yyyy-MM}.gz"/>
    </rollingPolicy>
    <param name="Append" value="true" />
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%c{1} - %m%n"/>
    </layout>
  </appender>
  <root">
    <appender-ref ref="ROLL"/>
  </root>
</log4j:configuration>

Praful
May 13, 2014
Hi below is my log4j.xml snippet, when my web application is deployed in websphere, log files are getting overwritten instead of backup files. Kindly guide me.
Reply
- Lokesh
  May 13, 2014
  Can’t see anything…:-( Please paste the code inside [ xml ]…[ /xml ] tag (without spaces in opening and closing tag ).
  Reply
4XD7
May 12, 2014
Where save the files with this configuration?
Reply
mateen
October 8, 2013
is it possible to code the entire log4j java file without xml and without properties if yes then please upload and update me
Reply
- Lokesh Gupta
  October 8, 2013
  Read “Automatic Configuration” section in : http://logging.apache.org/log4j/2.x/manual/configuration.html
  “If no configuration file could be located the DefaultConfiguration will be used. This will cause logging output to go to the console.”
  Reply

Ask Questions & Share Feedback Cancel reply

Your email address will not be published. Required fields are marked *

Comment

*Want to Post Code Snippets or XML content? Please use [java] ... [/java] tags otherwise code may not appear partially or even fully. e.g.

[java] 
public static void main (String[] args) {
...
} 
[/java]

Name *

Email *

Website

Help me fight spammers. Solve this simple math. * 7 + 8 =