log4j - File & Format

Sample codes to configure log4j

General logger initialization

 Logger logger = Logger.getLogger(YourClass.class);

log4j.properties file sample (writes to file too)

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.Target=System.out

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

#log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

#log4j.appender.stdout.layout.ConversionPattern=%d{DATE} %5p [%c]:%L - %m%n
#log4j.appender.stdout.layout.ConversionPattern=%d{ISO8601} %5p [%c]:%L - %m%n
#Same as ISO8601
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd'T'HH:mm:ss.S Z} %5p [%c]:%L - %m%n

log4j.appender.stdout.Threshold=trace

log4j.appender.file=org.apache.log4j.RollingFileAppender

log4j.appender.file.File=${user.dir}/you_log_file.log

log4j.appender.file.MaxFileSize=10MB

log4j.appender.file.MaxBackupIndex=10

log4j.appender.file.layout=org.apache.log4j.PatternLayout

### set log levels - for more verbose logging change 'info' to 'debug' ###

log4j.rootLogger=trace, stdout, file

Additional file outputs [2 sample layouts]

//Load the file handler for the logger 1

Appender fh = new FileAppender(new SimpleLayout(),  workingDir + File.separator + logfile);

logger.addAppender(fh);

fh.setLayout(new SimpleLayout());

//Load the file handler for the logger 2

TTCCLayout logLayout = new TTCCLayout();

logLayout.setDateFormat("dd MMM yyyy HH:mm:ss,SSS");

Appender fh = new FileAppender(logLayout,  workingDir + File.separator + logfile);

logger.addAppender(fh);

fh.setLayout(logLayout);

More options available with 'Enhanced Pattern Layout' and 'Layout'

Ref:

http://www.mkyong.com/logging/log4j-log4j-properties-examples/

http://stackoverflow.com/questions/4474646/how-to-write-to-a-text-file-using-to-log4j

API:

https://logging.apache.org/log4j/1.2/apidocs/index.html