Logging in Tomcat

wdx1992828

　　Tomcat 5.5 has done away with localhost_log which you may be  familiar with as the runtime exception/stack trace log. These types of error are  usually thrown by uncaught exceptions, but are still valuable to the developer.  They can now be found in the stdout log.
　　If you need to setup cross-context detailed logging from within Tomcat's  code, then you can use a simple log4j configuration. Note that this logging van  be very verbose depending on the log level you chose to use. Note also that a  log4j logging configuration is not going to produce stack trace type logging:  those stack traces are output to stdout as discussed above.
　　Follow the following steps to setup a file named tomcat.log that has internal  Tomcat logging output to it:

• Create a file called log4j.properties with the following content and save it  into common/classes.
  

  http://xiaoruanjian.iteye.com/blog/./images/void.gif	http://xiaoruanjian.iteye.com/blog/./images/void.gif	http://xiaoruanjian.iteye.com/blog/./images/void.gif
  http://xiaoruanjian.iteye.com/blog/./images/void.gif	log4j.rootLogger=DEBUG, R             log4j.appender.R=org.apache.log4j.RollingFileAppender             log4j.appender.R.File=${catalina.home}/logs/tomcat.log             log4j.appender.R.MaxFileSize=10MB             log4j.appender.R.MaxBackupIndex=10             log4j.appender.R.layout=org.apache.log4j.PatternLayout             log4j.appender.R.layout.ConversionPattern=%p %t %c - %m%n	http://xiaoruanjian.iteye.com/blog/./images/void.gif
  http://xiaoruanjian.iteye.com/blog/./images/void.gif	http://xiaoruanjian.iteye.com/blog/./images/void.gif	http://xiaoruanjian.iteye.com/blog/./images/void.gif

  
  
• 
  Download Log4J (v1.2 or later)  and place the log4j jar in $CATALINA_HOME/common/lib.
  
• 
  Download  Commons Logging and place the commons-logging.jar (not  commons-logging-api.jar) in $CATALINA_HOME/common/lib with the log4j jar.
  
• Start Tomcat
  

　　This log4j configuration sets up a file called tomcat.log in your Tomcat logs  folder with a maximum file size of 10MB and up to 10 backups. DEBUG level is  specified which will result in the most verbose output from Tomcat.
　　You can (and should) be more picky about which packages to include in the  logging. Tomcat 5.5 uses defines loggers by Engine and Host names. For example,  for a default Catalina localhost log, add this to the end of the  log4j.properties above. Note that there are known issues with using this naming  convention (with square brackets) in log4j XML based configuration files, so we  recommend you use a properties file as described until a future version of log4j  allows this convention.  

• log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=DEBUG,  R
  
• log4j.logger.org.apache.catalina.core=DEBUG, R
  
• log4j.logger.org.apache.catalina.session=DEBUG, R
  

Be warned a  level of DEBUG will produce megabytes of logging and slow startup of Tomcat.  This level should be used sparingly when debugging of internal Tomcat operations  is required.　　Your web applications should certainly use their own log4j configuration.  This is valid with the above configuration. You would place a similar  log4j.properties file in your web application's WEB-INF/classes folder, and  log4j1.2.8.jar into WEB-INF/lib. Then specify your package level logging. This  is a basic setup of log4j which does *not* require Commons-Logging, and you  should consult the log4j  documentation for more options. This page is intended only as a  bootstrapping guide.