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# log4j

## Tutorial log4j 2

https://howtodoinjava.com/log4j2/

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

log4j 2 Mini-Tutorial
*********************
comments by Ru
more infos see: https://logging.apache.org/log4j/2.x/
example from 
https://bitbucket.org/docuteam/cosmos/src/master/docuteam-feeder/src/main/resources/log4j2.xml
-->

<Configuration
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://logging.apache.org/log4j/2.0/config"
    xmlns="http://logging.apache.org/log4j/2.0/config" status="WARN"
    strict="true">

    <!-- 
        Properties are like variables, that will be used in the Appenders section
    -->
    <Properties>

        <!-- 
            set property "name" to "feeder", which will be used in the appender ROLLINGFILE
        -->
        <Property name="name">feeder</Property>

        <!-- 
            set property "pattern", which will be used in the appender ROLLINGFILE
        -->
        <Property name="pattern">%-5p %d{dd.MM.yyyy HH:mm:ss.SSS} (%c{2}.%M()[%L]) %m%n</Property>
    </Properties>

    <!-- 
        The APPENDER object is responsible for publishing logging information to various preferred destinations such as a database, file, console, UNIX Syslog, etc. 
    -->
    <Appenders>
        <!-- 
            Output to console
            - type: must be "Console"
            - target: decide on which console the outut will be transferred to. 
              The OS has 2 (or 3) consoles. One for output, one for only errors.
        -->
        <Appender type="Console" name="STDOUT" target="SYSTEM_OUT">
            <PatternLayout pattern="${pattern}" charset="UTF-8" />
        </Appender>

        <Appender type="Console" name="STDERR" target="SYSTEM_ERR">
            <PatternLayout pattern="${pattern}" charset="UTF-8" />
        </Appender>

        <!-- 
            Output in log file
            - fileName: Path/filename with the property ${name}
            - filePattern: Path/filename for the archived log files (when rollover occurs)
        -->
        <RollingFile name="ROLLINGFILE"
            fileName="logs/${name}.log"
            filePattern="logs/${name}-%d{yyyy-MM-dd}-%i.log.gz">

            <!--
                set output pattern according to the property ${pattern}
            -->
            <PatternLayout pattern="${pattern}" charset="UTF-8" />

            <!--
                The policy to use to determine if a rollover should occur.

                The following XML fragment defines policies that rollover the log when the log size reaches 20 megabytes, and when the current date no longer matches the log’s start date.
            -->         
            <Policies>
                <TimeBasedTriggeringPolicy />
                <SizeBasedTriggeringPolicy size="20 MB" />
            </Policies>

            <!--
                if the fileIndex attribute is set to "nomax" then the min and max values will be ignored and file numbering will increment by 1 and each rollover will have an incrementally higher value with no maximum number of files.
            -->
            <DefaultRolloverStrategy fileIndex="nomax">

                <!-- 
                    Cleanup
                -->
                <Delete basePath="logs" maxDepth="1">

                    <!-- 
                        Delete oldest log files if they are older than 30 days or total accumulated size exceeds 1 GB 
                    -->
                    <IfFileName glob="${name}-*.log.gz">
                        <IfAny>
                            <IfLastModified age="30d" />
                            <IfAccumulatedFileSize exceeds="1 GB"/>
                        </IfAny>
                    </IfFileName>
                </Delete>
            </DefaultRolloverStrategy>
        </RollingFile>
    </Appenders>

    <!-- 
        The top-level layer is the LOGGER which provides the Logger object. The Logger object is responsible for capturing logging information and they are stored in a namespace hierarchy. 
    -->
    <Loggers>
        <!-- 
            set logger for class "ch.docuteam" to level "debug"

            there is no ref, meaning that the output will be the same for each appender.
        -->     
        <Logger name="ch.docuteam" level="debug" />

        <!-- 
            set logger for class "ch.docuteam.feeder", which is a child for ch.docuteam, to level "debug"
            Once an event reaches a logger with its additivity set to false the event will not be passed to any of its parent loggers

            for appender STDOUT we set to level "info"
            for appender STDERR we set to level "error"
            for appender ROLLINGFILE we use default level "info"
        -->
        <Logger name="ch.docuteam.feeder" level="debug" additivity="false">
            <AppenderRef ref="STDOUT" level="info" />
            <AppenderRef ref="STDERR" level="error" />
            <AppenderRef ref="ROLLINGFILE" />
        </Logger>
        <!-- Minimize logging for ch.docuteam.feeder.qualityassurance.SIPVirusCheck -->
        <Logger
            name="ch.docuteam.feeder.qualityassurance.SIPVirusCheck.VirusScannerClam"
            level="info" additivity="false">
            <AppenderRef ref="STDOUT" level="warn" />
            <AppenderRef ref="STDERR" level="error" />
            <AppenderRef ref="ROLLINGFILE" />
        </Logger>
        <Logger
            name="com.artofsolving.jodconverter.openoffice.connection.AbstractOpenOfficeConnection"
            level="info" />
        <Logger name="fedora.services.diringest" level="info" />
        <Logger name="org.apache.axis" level="info" />
        <Logger name="org.icepdf.core.pobjects.Catalog" level="info" />
        <!-- Avoid messages like "will always scan up to maximum bytes." -->
        <Logger
            name="uk.gov.nationalarchives.droid.core.signature.droid6.InternalSignature"
            level="error" />
        <Logger name="uk.gov.nationalarchives.droid.xmlReader"
            level="error" />

        <!-- 
            Here come the default (root) outputs...
            by default, only shows messages from WARN onwards: WARN < ERROR < FATAL
        -->
        <Root level="warn">

            <!-- 
                set log level of appender STDOUT to "warn".
                it actually isn't nescessary, as we defined the standard to "warn" already.
            -->
            <AppenderRef ref="STDOUT" level="warn" />

            <!-- 
                set log level of appender STDERR to "error", 
                because we decide that the standard "warn" is not enough.
            -->
            <AppenderRef ref="STDERR" level="error" />

            <!-- 
                set log level of appender ROLLINGFILE to "debug"
             -->
            <AppenderRef ref="ROLLINGFILE" level="debug" />
        </Root>
    </Loggers>

</Configuration>
```

## Tutorial log4j

https://howtodoinjava.com/log4j

## Example (log4j 1)


``` xml
<!-- 

log4j
*****

more infos see: https://logging.apache.org/log4j/2.x/

this example taken from fedoragsearch on nwvappdafed001t.adtest.noel.gv.at

comments by roger rutishauser -->




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

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




  <!-- The APPENDER object is responsible for publishing logging information to various preferred destinations such as a database, file, console, UNIX Syslog, etc. 
  -->

  <!-- output in console with ConsoleAppender -->
  <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">

    <!-- The LAYOUT layer provides objects which are used to format logging information in different styles. It provides support to appender objects before publishing logging information. 
    there are different ways, PatternLayout is one of them. 
    more info: https://www.tutorialspoint.com/log4j/log4j_log_formatting.htm
    -->
    <layout class="org.apache.log4j.PatternLayout">

      <!-- value explained: 
      %p priority of logging event
      %d output date 
      %c{1} used to output the category of the logging event
      %m output the application supplied message associated with the logging event
      %n outputs platform dependent line separator character(s)
      -->
      <param name="ConversionPattern" value="%p %d (%c{1}) %m%n"/>
    </layout>
  </appender>

  <!-- output in file
  https://www.tutorialspoint.com/log4j/log4j_logging_files.htm 
  -->
  <!-- create daily log file with DailyRollingFileAppender-->
  <appender name="FILEOUT" class="org.apache.log4j.DailyRollingFileAppender">
    <!-- path to log file -->
    <param name="File" value="${catalina.base}/logs/fedoragsearch.daily.log"/>
    <!-- beispiel: fedoragsearch.daily.log.2020-10-21 -->
    <param name=" " value="'.'yyyy-MM-dd"/>
    <layout class="org.apache.log4j.PatternLayout">
      <!-- explanation see above -->
      <param name="ConversionPattern" value="%p %d (%c{1}) %m%n"/>
    </layout>
  </appender>
  


  <!-- create daily log file with DailyRollingFileAppender and limit to also to size -->
  <appender name="FILEOUT" class="org.apache.log4j.DailyRollingFileAppender">
    <rollingPolicy class="org.apache.log4j.rolling.TimeBasedRollingPolicy">

        <!-- path to log file -->
        <param name="File" value="${catalina.base}/logs/fedoragsearch.daily.log"/>
        <!-- beispiel: fedoragsearch.daily.log.2020-10-21 -->
        <param name="DatePattern" value="'.'yyyy-MM-dd"/>
    </rollingPolicy>
    <triggeringPolicy class="org.apache.log4j.rolling.SizeBasedTriggeringPolicy">
        <param name="MaxFileSize" value="10MB" />
    </triggeringPolicy>
    <layout class="org.apache.log4j.PatternLayout">
      <!-- explanation see above -->
      <param name="ConversionPattern" value="%p %d (%c{1}) %m%n"/>
    </layout>
  </appender>



  <!-- The top-level layer is the LOGGER which provides the Logger object. The Logger object is responsible for capturing logging information and they are stored in a namespace hierarchy. 
  -->
  <logger name="dk.defxws.fedoragsearch" additivity="false">

    <!-- The LEVEL object defines the granularity and priority of any logging information.
    For the standard levels, we have 
    ALL (trace) < DEBUG < INFO < WARN < ERROR < FATAL < OFF.

    here we get all messages from DEBUG onwards: DEBUG < INFO < WARN < ERROR < FATAL
    -->
    <level value="DEBUG" />
    <appender-ref ref="FILEOUT"/>
  </logger>

  <logger name="dk.defxws.fgszebra" additivity="false">
    <level value="DEBUG" />
    <appender-ref ref="FILEOUT"/>
  </logger>
  
  <logger name="dk.defxws.fgslucene" additivity="false">
    <level value="DEBUG" />
    <appender-ref ref="FILEOUT"/>
  </logger>
  
  <logger name="dk.defxws.fgssolr" additivity="false">
    <level value="DEBUG" />
    <appender-ref ref="FILEOUT"/>
  </logger>

  <root>
    <!-- in this file, the console output only shows messages from WARN onwards: WARN < ERROR < FATAL
    -->
    <level value="WARN" />
    <appender-ref ref="STDOUT"/>
  </root>
  
</log4j:configuration>
```