log4j: Log output of a specific class to a specific appender

Question

I use log4j and would like to route the output of certain Loggers to specific files.

I already have multiple appenders in place. Now, to make debugging easier, I want to tell log4j that the output generated by a specific class (eg foo.bar.Baz) should be written to a specific log file.

Can this be done?

Answer 1

An example:

log4j.rootLogger=ERROR, logfile

log4j.appender.logfile=org.apache.log4j.DailyRollingFileAppender
log4j.appender.logfile.datePattern='-'dd'.log'
log4j.appender.logfile.File=log/radius-prod.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%-6r %d{ISO8601} %-5p %40.40c %x - %m\n

log4j.logger.foo.bar.Baz=DEBUG, myappender
log4j.additivity.foo.bar.Baz=false

log4j.appender.myappender=org.apache.log4j.DailyRollingFileAppender
log4j.appender.myappender.datePattern='-'dd'.log'
log4j.appender.myappender.File=log/access-ext-dmz-prod.log
log4j.appender.myappender.layout=org.apache.log4j.PatternLayout
log4j.appender.myappender.layout.ConversionPattern=%-6r %d{ISO8601} %-5p %40.40c %x - %m\n

Answer 2

Here's an answer regarding the XML configuration, note that if you don't give the file appender a ConversionPattern it will create 0 byte file and not write anything:

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

<log4j:configuration 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="%-5p %c{1} - %m%n"/>
        </layout>
    </appender>

    <appender name="bdfile" class="org.apache.log4j.RollingFileAppender">
        <param name="append" value="false"/>
        <param name="maxFileSize" value="1GB"/>
        <param name="maxBackupIndex" value="2"/>
        <param name="file" value="/tmp/bd.log"/>
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%-5p %c{1} - %m%n"/>
        </layout>
    </appender>

    <logger name="com.example.mypackage" additivity="false">
        <level value="debug"/>
        <appender-ref ref="bdfile"/>
    </logger>

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

</log4j:configuration>

Answer 3

Here is an example for logging details into separate files:

#property settings
property.LOG_DIR = /opt/logs/app_name/

#Console appenders
appender.console.type = Console
appender.console.name = STDOUT
appender.console.layout.type = PatternLayout
appender.console.layout.pattern = %d{yy/MM/dd HH:mm:ss.SSS} %p %c{1}: %m%n

#root loggers
rootLogger.level = INFO
rootLogger.appenderRef.stdout.ref = STDOUT
rootLogger.appenderRefs = stdout
rootLogger.appenderRef.files.ref = Rolling

# Rolling file appender
appender.rolling.type = RollingFile
appender.rolling.name = Rolling
appender.rolling.fileName= ${LOG_DIR}/application.log
appender.rolling.filePattern= ${logFile}.%i
appender.rolling.layout.type=PatternLayout
appender.rolling.layout.pattern=%d{yy/MM/dd HH:mm:ss.SSS} %p %c{1}: %m%n
appender.rolling.policies.type=Policies
appender.rolling.policies.size.type = SizeBasedTriggeringPolicy
appender.rolling.strategy.type = DefaultRolloverStrategy
appender.rolling.policies.size.size=50MB
appender.rolling.strategy.max=20

#custom logging for audit-viewer
logger.aduit.name = auditlogger
logger.aduit.level = info
logger.aduit.appenderRefs = auditRef
logger.aduit.appenderRef.auditRef.ref = AuditAppender
logger.aduit.additivity = false

# Logging audit details to dedicated file
appender.aduitfile.type = File
appender.aduitfile.fileName = ${LOG_DIR}/audit.log
appender.aduitfile.name = AuditAppender
appender.aduitfile.layout.type = PatternLayout
appender.aduitfile.layout.pattern = %d{yy/MM/dd HH:mm:ss.SSS} %p %c{1}: %m%n

# Settings to quiet third party or custom logs that are too verbose
loggers = mongodb, aduit

logger.mongodb.name=org.mongodb.driver.cluster
logger.mongodb.level=ERROR

Here if you wish to have logs from some class into separate file, like auditlogger then use it inside a class as follows:

  private val logger = LogManager.getLogger("auditlogger") //dont change this appender ref
  logger.info("Find me inside 'audit.log' file")