设置tomcat 5.5版本的Log4j日志功能

在tomcat 5.5中好象没有早期版本的log功能,为了能让tomcat使用者方便的查看web应用中出现的错误,以便调试程序,可以手工配置log日志输出。步要步骤如下：

1. 我们可以在tomcat 5.5/common/classes/下创建一个log4j.properties文件,内容如下

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
log4j.logger.org.apache.catalina=debug, R

建议日志级别设为error,因为debug输出的内容过多,反而不宜查看.设置方式是把log4j.properties中的第一行和最后一行的debug改为error。

2. 将commons-logging.jar和log4j.jar复制到${catalina.home}/common/lib目录下。重启tomcat服务器，在tomcat 5.5/log/里出现tomcat.log日志文档.

tomcat官方网站上给出了log4j在tomcat中应用的说明文档,下面即是摘录的一段说明文档:

log4j
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:
1. Create a file called log4j.properties with the following content and save it into common/classes.
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
log4j.logger.org.apache.catalina=DEBUG, R

2. Download Log4J (v1.2 or later) and place the log4j jar in $CATALINA_HOME/common/lib.
3. Download Commons Logging and place the commons-logging.jar (not commons-logging-api.jar) in $CATALINA_HOME/common/lib with the log4j jar.
4. 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.