How does log4j load the config files ?

Add -Dlog4j.debug to the command line.


trace file :

log4j: Trying to find [log4j.xml] using context classloader sun.misc.Launcher$AppClassLoader@11b86e7.
log4j: Trying to find [log4j.xml] using sun.misc.Launcher$AppClassLoader@11b86e7 class loader.
log4j: Trying to find [log4j.xml] using ClassLoader.getSystemResource().
log4j: Trying to find [log4j.properties] using context classloader sun.misc.Launcher$AppClassLoader@11b86e7.
log4j: Trying to find [log4j.properties] using sun.misc.Launcher$AppClassLoader@11b86e7 class loader.
log4j: Trying to find [log4j.properties] using ClassLoader.getSystemResource().
log4j: Could not find resource: [null].
ControlListener Created




Links :
http://jaitechwriteups.blogspot.com/2006/07/know-how-log4j-tries-to-configure.html
http://jaikiran.wordpress.com/2006/07/05/i-get-log4jwarn-no-appenders-could-be-found-for-logger-message-2/
 

How to enable Log4j logging in Eclipse console window?

Problems:

Could not see the log message in eclipse console window but it shows following warning message

log4j:WARN No appenders could be found for logger (com.test.HelloWorld).

log4j:WARN Please initialize the log4j system properly.

Reasons:
Log4j is not initialised.

Solution:
Add a ConsoleAppender or Appender

Code Sample:
BasicConfigurator.configure();
or
PropertyConfigurator.configure("log4j.xml");

Ref:

Log4j Manual
Log4j API
BasicConfigurator
PropertyConfigurator

Log4j warning message [log4j:WARN No appenders could be found for logger]

Log4j:

Log4j is a logging or tracing API, large number of applications and framework use Log4j for logging.

Problems:

Sometimes application do not generate log files and generate the following warning message.

log4j:WARN No appenders could be found for logger (com.test.HelloWorld).
log4j:WARN Please initialize the log4j system properly.

Reasons:

Log4j is not initialised properly. The Log4j library files are in application class path but Log4j configuration file is not in application class path.

Solution:

Add log4j configuration file [log4j.properties or log4j.xml] to class path.

More Info:

Log4j priority order,
FATAL: 50000
ERROR: 40000
WARN: 30000
INFO: 20000
DEBUG: 10000

Ref:
log4j Manual
log4j API