Troubleshooting logging configuration (Log4j, commons-logging)
Did it ever happen to you that your logging didn't behave as expected? Here are some tips how to find out what's going on.
Extract of a sample output (no commons-logging.properties):
Extract of a sample output (incorrect commons-logging.properties found):
Notice that Commons Logging uses the context classloader and not e.g. Class.getClassloader() to locate the implementation to use, which may occassionally lead to some problems.
PS: You may be better of not using commons-logging because of its classloader issues. (SLF4J may be better?)
Example output:
For the log4j.properties:
Commons-logging (since 1.1)
Set the system propertyorg.apache.commons.logging.diagnostics.dest to STDOUT (or STDERR or a file name); docs: -Dorg.apache.commons.logging.diagnostics.dest=STDOUTExtract of a sample output (no commons-logging.properties):
...
[LogFactory from sun.misc.Launcher$AppClassLoader@934873913] [ENV] Application classpath (java.class.path): ..
...
[LOOKUP] No properties file of name 'commons-logging.properties' found
....
Discovering a Log implementation...
...
Log adapter 'org.apache.commons.logging.impl.Log4JLogger' from classloader java.net.URLClassLoader@32689826 has been selected for use.
Extract of a sample output (incorrect commons-logging.properties found):
...
[LogFactory from sun.misc.Launcher$AppClassLoader@934873913] [LOOKUP] Properties file found at 'jar:file:/myproject/lib/test/dbunit-embeddedderby-parenttest-sources.jar!/commons-logging.properties' with priority 0.0
.. [LOOKUP] Properties file at 'file:/myproject/web/WEB-INF/classes/commons-logging.properties' with priority 0.0 does not override file at 'jar:file:/myproject/lib/test/dbunit-embeddedderby-parenttest-sources.jar!/commons-logging.properties' with priority 0.0
.. [LOOKUP] Properties file of name 'commons-logging.properties' found at 'jar:file:/myproject/lib/test/dbunit-embeddedderby-parenttest-sources.jar!/commons-logging.properties"
.. Attempting to load user-specified log class 'org.apache.commons.logging.impl.SimpleLog'...
.. Log adapter 'org.apache.commons.logging.impl.SimpleLog' from classloader sun.misc.Launcher$AppClassLoader@934873913 has been selected for use.
...
Notice that Commons Logging uses the context classloader and not e.g. Class.getClassloader() to locate the implementation to use, which may occassionally lead to some problems.
PS: You may be better of not using commons-logging because of its classloader issues. (SLF4J may be better?)
Log4j
Set the system property log4j.debug to true for Log4j to log the location of the configuration file it's using and other useful information. You can also set it in in the log4j.properties file:log4j.debug=trueOr, as mentioned above, pass it as a system property to Java, for example as in
java -Dlog4j.debug=true -jar YourApplication.jarExample output:
log4j: Parsing for [root] with value=[INFO, CONSOLE, filelog].
log4j: Level token is [INFO].
log4j: Category root set to INFO
log4j: Parsing appender named "CONSOLE".
log4j: Parsing layout options for "CONSOLE".
log4j: Setting property [conversionPattern] to [%6rms [%p] ..%0.46c %x- %m%n].
log4j: End of parsing for "CONSOLE".
log4j: Parsed "CONSOLE" options.
log4j: Parsing appender named "filelog".
log4j: Parsing layout options for "filelog".
log4j: Setting property [conversionPattern] to [%6rms [%p] ..%0.46c %x- %m%n].
log4j: End of parsing for "filelog".
log4j: Setting property [file] to [/home/me/mylog.log].
log4j: Setting property [maxBackupIndex] to [5].
log4j: Setting property [maxFileSize] to [50MB].
log4j: setFile called: /home/me/mylog.log, true
log4j: setFile ended
log4j: Parsed "filelog" options.
log4j: Parsing for [eu.ibacz.lqs.uiradrupdater] with value=[DEBUG].
log4j: Level token is [DEBUG].
log4j: Category eu.ibacz.lqs.uiradrupdater set to DEBUG
log4j: Handling log4j.additivity.eu.ibacz.lqs.uiradrupdater=[null]
log4j: Finished configuring.
For the log4j.properties:
log4j.rootCategory=INFO, CONSOLE, filelog
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%6rms [%p] ..%0.46c %x- %m%n
log4j.appender.filelog=org.apache.log4j.RollingFileAppender
log4j.appender.filelog.File=${user.home}/mylog.log
log4j.appender.filelog.MaxFileSize=50MB
log4j.appender.filelog.MaxBackupIndex=5
log4j.appender.filelog.layout=org.apache.log4j.PatternLayout
log4j.appender.filelog.layout.ConversionPattern=%6rms [%p] ..%0.46c %x- %m%n
log4j.logger.eu.ibacz.lqs.uiradrupdater=DEBUG