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How to log warn only in log4j

In Struts 2 application we use log4j for logging. I want to log only warn but when i try to use in my log4j.properties
log4j.rootLogger=warn, stdout
it prints error and fatal log too. I want only warn log. I read the levels of log in some tutorials. So I know why error and fatal prints, because they are less priority than warn. How to print warn log only in my console?
My Java code:
import org.apache.log4j.Logger;
public class LogClass {
private static final org.apache.log4j.Logger log = Logger.getLogger(LogClass.class);
public static void main(String[] args) {
log.trace("Trace");
log.debug("Debug");
log.info("Info");
log.warn("Warn");
log.error("Error");
log.fatal("Fatal");
}
}
Any help will be greatly appreciated!

Use the org.apache.log4j.varia.LevelRangeFilter filter. Your XML configuration file could be:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"
debug="false">
<appender name="warn-out" class="org.apache.log4j.FileAppender">
<param name="File" value="warn.log" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%m%n" />
</layout>
<filter class="org.apache.log4j.varia.LevelRangeFilter">
<param name="LevelMax" value="warn" />
<param name="LevelMin" value="warn" />
<param name="AcceptOnMatch" value="true" />
</filter>
</appender>
<appender name="console" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%m%n" />
</layout>
<filter class="org.apache.log4j.varia.LevelRangeFilter">
<param name="LevelMax" value="warn" />
<param name="LevelMin" value="warn" />
<param name="AcceptOnMatch" value="true" />
</filter>
</appender>
<root>
<level value="warn" />
<appender-ref ref="warn-out" />
<appender-ref ref="console" />
</root>
</log4j:configuration>
For more options go here.
It looks like properties file configuration does not support filters. The following is taken from log4j's official wiki:
Filter is not supported by PropertiesConfigurator.
EDIT: Added console appender as well to the XML and turned off debug for log4j. Now it should go to both file and console.

how to Create a folder for log file using log4j.xml

I just created log4j.xml file like ,
<?xml version="1.0" encoding="UTF-8"?>
<log4j:configuration>
<appender name="fileAppender" class="org.apache.log4j.RollingFileAppender">
<param name="Threshold" value="ALL" />
<param name="MaxFileSize" value="512KB" />
<param name="MaxBackupIndex" value="10" />
<param name="File" value="F:/Core_logs/application_log.log" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d{MMM-dd-yyyy HH:mm:ss:SSS} %-5p %m%n"/>
</layout>
</appender>
<!--sets the priority log level for org.springframework -->
<logger name="org.springframework">
<level value="info" />
</logger>
<!--sets the default priority log level -->
<root>
<priority value="all"></priority>
<appender-ref ref="fileAppender" />
</root>
</log4j:configuration>
But I have the exception as ,
java.io.FileNotFoundException: F:\Spring_Core_logs\pointel_Aop.log (The system cannot find the path specified)
If I created a folder Core_logs manually in the particular location means, it works fine and log file created.
How to create the folder , if the folder is not exist in a particular location?

EDIT:
This here could also help you/looks like the best solution for you:
Configuring Java FileHandler Logging to create directories if they do not exist
It seems like log4j version 1.2.15 does it. Look for an answer below from Arun P Johny, he posted a piece of code from the log4j sourcecode. I overlooked it because it was not accepted as an answer.

Log4j.xml file for creating in your eclipse
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/" debug="false">
<appender name="fileAppender" class="org.apache.log4j.FileAppender">
<param name="Threshold" value="INFO" />
<param name="Append" value="true" />
<param name="File" value="logfile.log"/>
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d %-5p [%c{1}] %m %n" />
</layout>
</appender>
<root>
<level value="INFO"/>
<appender-ref ref="fileAppender"/>
</root>
</log4j:configuration>"UTF-8"?>

create two log files using RollingFileAppender in log4j.xml

My log4j.xml configuration was like ,
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd" >
<log4j:configuration>
<appender name="fileAppender1" class="org.apache.log4j.RollingFileAppender">
<param name="Threshold" value="ALL" />
<param name="MaxFileSize" value="3KB" />
<param name="MaxBackupIndex" value="10" />
<param name="File" value="F:/logs/Testing/Project_moduleOne.log" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d{MMM-dd-yyyy HH:mm:ss:SSS} %-5p %m%n" />
</layout>
</appender>
<appender name="fileAppender2" class="org.apache.log4j.RollingFileAppender">
<param name="Threshold" value="ALL" />
<param name="MaxFileSize" value="3KB" />
<param name="MaxBackupIndex" value="10" />
<param name="File" value="F:/logs/PAD_Testing/Project_moduleTwo.log" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d{MMM-dd-yyyy HH:mm:ss:SSS} %-5p %m%n" />
</layout>
</appender>
<!--sets the priority log level for org.springframework -->
<logger name="com.comp.logger1">
<appender ref="fileAppender1"/>
</logger>
<logger name="com.comp.logger2">
<appender ref="fileAppender2" />
</logger>
<!--sets the default priority log level -->
<root>
<priority value="all"></priority>
<appender-ref ref="fileAppender1" />
<appender-ref ref="fileAppender2" />
</root>
</log4j:configuration>
And two log files also created in the specified location.
I need to know how to log two different data's in these two different log_files independently in JAVA class.
For example,
Logger logOne = Logger.getLogger("com.comp.logger1");
Logger logTwo = Logger.getLogger("com.comp.logger2");
The above code is not working for me. All the log informations are logged to both the created two log files. I need the separation of logging data.
My need is ,
I want to create two log file. Because my project has two modules and log each module in separate log files.
After that , I have to log each module logging data independently .
Please make sure I used the logger name for logging in my java class correctly.
Any new or complete examples using log4j.xml are greatly appreciated.
EDIT :
If I add the additivity="false" in the logger as,
<logger name="com.comp.logger1" additivity="false">
<appender ref="fileAppender1" />
</logger>
<logger name="com.comp.logger2" additivity="false">
<appender ref="fileAppender2" />
</logger>
The log data didn't logged in the created log file.The log file was empty.
Please make sure my <root>...</root> is correct.

You problem is with the <root> section, the root section captures all logs, and you've told it to log to both appenders...
You could remove it, or set additivity="false" on each of your logger elements - this will tell log4j not to log the same log through 'root' if it's already been logged through one of your 'logger's.
Edit: you don't say which version of log4j you are using, but I'm using log4j-1.2.16, and using the file in your post, it fails completely for me because it doesn't like the <appender ref="fileAppender1"/>, it wants them to be <appender-ref ref="fileAppender1"/> (note the -ref after the appender). If I add these in, and also add the additivity attributes that I suggested, then for me it works as you expect.

SLF 4j Logs are not written to log

Logs are not written properly
slf version slf4j-api-1.7.5.jar, slf4j-log4j12-1.7.5.jar, log4j-1.2.16.jar
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<!-- log4j generic catchall for adapters. -->
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
<!-- Example DailyRollingFile appender, this is the preferred logging appender -->
<appender name="CommonAdapterAppender" class="org.apache.log4j.DailyRollingFileAppender">
<param name="file" value="/opt/adapter.log" />
<param name="encoding" value="UTF-8" />
<param name="append" value="true" />
<!-- Rollover at the top of every hour -->
<param name="DatePattern" value="'.'yyyy-MM-dd-HH" />
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern"
value="%d{yyyy-MM-dd HH:mm:ss.SSS-zzz} %5p [%t] %c{1} - %m%n" />
</layout>
</appender>
<!-- Categories -->
<category name="com.other" additivity="false">
<priority value="warn" />
</category>
<logger name="com.adapter" additivity="false">
<level value="debug" />
<appender-ref ref="CommonAdapterAppender"/>
</logger>
<logger name="com.adaptations" additivity="false">
<level value="debug" />
<appender-ref ref="CommonAdapterAppender"/>
</logger>
<root>
<priority value="error" />
<appender-ref ref="CommonAdapterAppender" />
<!-- <appender-ref ref="SyslogAppender"/> -->
</root>
</log4j:configuration>
The above log4j file is used by multiple adapters. First time it is writing to adapter.log and after that only some component logs are written. Also I have noticed that after the second time it is writing few logs to adapter.log..
I cannot understand what is going wrong here. Can someone please help me out?

I believe you should be using a single shared log 4J configuration and instance for all your adapters if you want to use the the same log file.
As is, Log 4j instances are probably competing for the control of the file.

Send Log4J INFO to database and DEBUG to Console?

I have com.mycompany.library.*
I want DEBUG go to console, and INFO go to DB. how I can achieve it?
this is part of my log4j.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration debug="false"
xmlns:log4j="http://jakarta.apache.org/log4j/">
<!-- APPENDERS LIST -->
<!-- show log entries on console -->
<appender name="ConsoleApp" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">
<param name="ConversionPattern" value="%d{ISO8601} [%-5p][%-16.16t][%32.32c] - %m%n" />
</layout>
</appender>
<appender name="DBAppender" class="org.apache.log4j.jdbc.JDBCAppender">
<param name="URL" value="jdbc:postgresql://localhost:5432/myDB" />
<param name="driver" value="org.postgresql.Driver" />
<param name="user" value="postgres" />
<param name="password" value="password" />
<param name="sql"
value="INSERT INTO logs(user_id, dated,logger,lev,message) VALUES('%t', '%d{yyyy-MM-dd HH:mm:ss}','%-50c{3}','%p','%m')" />
</appender>
<logger name="com.mycompany">
<level value="INFO" />
<appender-ref ref="DBAppender" />
</logger>
<logger name="com.mycompany.library">
<level value="DEBUG" />
<appender-ref ref="ConsoleApp" />
</logger>
<root>
<priority value="ERROR" />
<appender-ref ref="DBAppender" />
</root>
</log4j:configuration>
With this config:
INFO and DEBUG goes to console. But Also INFO and DUBUG with double entries go to DB.
I want that to DB goes events with INFO level(and higher), not DEBUG. How to do that?

You can set a treshold on your appenders (not on the loggers). For instance:
<appender name="std-out" class="org.apache.log4j.ConsoleAppender">
<layout class="org.apache.log4j.PatternLayout">...</layout>
<param name="Threshold" value="info"/>
</appender>
See http://wiki.apache.org/logging-log4j/LogByLevel
edit: You also don't have to set an appender on both the com.mycompany logger and the root logger. This is why you have duplicate entries, because they are treated as additive (so at the level of com.mycompany, you essentially have 2 DB appenders).
Just set DBAppender on root and remove it from the com.mycompany logger.