How do I log from inside my web application in Tomcat 6.

Question

How do I log from within my web application deployed on Tomcat 6? Where should I expect the logging output to go (internal tomcat log files, or will another logfile be generated)? I see a ton of documentation but am having a hard time finding a direct answer to the above questions. Where should I expect the logging to show up (currently it is log4j is not generating a log file and it is not showing up in my console). I am trying to follow http://www.laliluna.de/articles/log4j-tutorial.html .

### direct log messages to stdout ###
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

### file appender
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.maxFileSize=100KB
log4j.appender.file.maxBackupIndex=5
log4j.appender.file.File=test.log
log4j.appender.file.threshold=info
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n

log4j.rootLogger=debug, stdout

In my application I define a log object:

private static org.apache.log4j.Logger log = Logger.getLogger(MyClass.class);
log.error("LOGGING!");

Thanks for the help.

Answer 1

IIRC Tomcat v4/v5 sends standard output to the catalina.out file, so any log4j output using a console appender would go to that file as well. Not sure if this still the case with newer versions of Tomcat, though.

Answer 2

2 things to try:

1: Change test.log to /tmp/test.log so you know exactly where the file is supossed to be.

2: Put your log4j.properties config file in your apache-tomcat-6.0.x/lib directory together with the log4j-1.2.15.jar file. And don't have any log4j files in your webapps/*/WEB-INF/lib

That's the way I am doing it, and its working for me. Here is a usefull snippet from my log4j.properties (Remember to do a mk /tmp/logs if you use this config)

log4j.rootLogger=debug, root
log4j.appender.root=org.apache.log4j.FileAppender
log4j.appender.root.layout = org.apache.log4j.PatternLayout
log4j.appender.root.layout.conversionPattern = %d [%t] %-5p %c - %m%n
log4j.appender.root.file = /tmp/logs/root.log
log4j.appender.root.append = true

log4j.category.mside = DEBUG,msideAppender
log4j.category.javashare = DEBUG,msideAppender

log4j.additivity.mside = false
log4j.additivity.mside.msideAppender = false
log4j.additivity.javashare = false

#Define msideAppender.
log4j.appender.msideAppender = org.apache.log4j.RollingFileAppender
log4j.appender.msideAppender.MaxFileSize=10MB
log4j.appender.msideAppender.MaxBackupIndex=7
log4j.appender.msideAppender.file = /tmp/logs/mside.log
log4j.appender.msideAppender.layout = org.apache.log4j.PatternLayout
log4j.appender.msideAppender.layout.conversionPattern = %d [%t] %-5p %c - %m%n
log4j.appender.msideAppender.append = true

Answer 3

BTW, use the system property -Dlog4j.debug system property. That should tell you where the heck log4j is sending its output.

Also, if your tomcat install is in a *nix system, or if you are running on Windows with cygwin installed, you could use the find command to detect what files get changed right after you send a HTTP request to Tomcat (which you know should produce a logging output)

cd <your tomcat install>    
ls -ltr `find . -type f -ls` | tail -10

That should show you the last 10 files that were updated or changed. It won't work if there are files in your app with spaces in their file names, though.

Answer 4

Your log4j configuration will be picked up by log4j if you put it into the classpath of your web application, e.g. in WEB-INF/classes/. Make sure that your log4j.jar is in WEB-INF/lib.

The output of the ConsoleAppender that you defined, which is logging on stdout, will go to ${CATALINA_BASE}/logs/catalina.out, as any Tomcat stdout output.

As to the RollingFileAppender, you should define the correct path. If you want your web application's logs to appear in Tomcat's logs directory, change the file for this appender to:

log4j.appender.file.File=${catalina.base}/logs/test.log