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Installation

Installation#

$ dnf install log4j log4j-web log4j-slf4j

Configuration#

Log4j configuration should be specified in log4j.configurationFile system property:

$ java -Dlog4j.configurationFile=log4j.xml ...

Default configuration file:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
  <Appenders>
    <Console name="Console" target="SYSTEM_OUT">
      <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
    </Console>
  </Appenders>
  <Loggers>
    <Root level="error">
      <AppenderRef ref="Console"/>
    </Root>
  </Loggers>
</Configuration>

More complex example:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="debug" strict="true" name="XMLConfigTest"
               packages="org.apache.logging.log4j.test">
  <Properties>
    <Property name="filename">target/test.log</Property>
  </Properties>
  <Filter type="ThresholdFilter" level="trace"/>

  <Appenders>
    <Appender type="Console" name="STDOUT">
      <Layout type="PatternLayout" pattern="%m MDC%X%n"/>
      <Filters>
        <Filter type="MarkerFilter" marker="FLOW" onMatch="DENY" onMismatch="NEUTRAL"/>
        <Filter type="MarkerFilter" marker="EXCEPTION" onMatch="DENY" onMismatch="ACCEPT"/>
      </Filters>
    </Appender>
    <Appender type="Console" name="FLOW">
      <Layout type="PatternLayout" pattern="%C{1}.%M %m %ex%n"/><!-- class and line number -->
      <Filters>
      <Filter type="MarkerFilter" marker="FLOW" onMatch="ACCEPT" onMismatch="NEUTRAL"/>
      <Filter type="MarkerFilter" marker="EXCEPTION" onMatch="ACCEPT" onMismatch="DENY"/>
      </Filters>
    </Appender>
    <Appender type="File" name="File" fileName="${filename}">
      <Layout type="PatternLayout">
        <Pattern>%d %p %C{1.} [%t] %m%n</Pattern>
      </Layout>
    </Appender>
  </Appenders>

  <Loggers>
    <Logger name="org.apache.logging.log4j.test1" level="debug" additivity="false">
      <Filter type="ThreadContextMapFilter">
        <KeyValuePair key="test" value="123"/>
      </Filter>
      <AppenderRef ref="STDOUT"/>
    </Logger>

    <Logger name="org.apache.logging.log4j.test2" level="debug" additivity="false">
      <AppenderRef ref="File"/>
    </Logger>

    <Root level="trace">
      <AppenderRef ref="STDOUT"/>
    </Root>
  </Loggers>

</Configuration>

Appender#

Console Appender#

<Console name="Console" target="SYSTEM_OUT">
  <PatternLayout pattern="%-5level: %msg%n"/>
</Console>

See also Console Appender.

Rolling File Appender#

<RollingFile name="RollingFile" fileName="logs/app.log"
             filePattern="logs/$${date:yyyy-MM}/app-%d{MM-dd-yyyy}-%i.log.gz">
  <PatternLayout pattern="%-5level: %msg%n"/>
  <Policies>
    <TimeBasedTriggeringPolicy />
    <SizeBasedTriggeringPolicy size="250 MB"/>
  </Policies>
</RollingFile>

See also Rolling File Appender.

Layout#

Pattern Layout#

<PatternLayout pattern="%-5level: %msg%n"/>

See also PatternLayout.

References#

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