loger in tomcat55

Logging in Tomcat
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Introduction
Tomcat 5.5 uses Commons Logging throughout its internal code allowing the developer to choose a logging configuration that suits their needs, e.g java.util.logging or Log4J. Commons Logging provides Tomcat the ability to log hierarchially across various log levels without needing to rely on a particular logging implementation.

An important consequence for Tomcat 5.5 is that the <Logger> element found in previous versions to create a localhost_log is no longer a valid nested element of <Context>. Instead, the default Tomcat configuration will use java.util.logging. If the developer wishes to collect detailed internal Tomcat logging (i.e what is happening within the Tomcat engine), then they should configure a logging system such as java.util.logging or log4j as detailed next.

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:


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
         
 
  

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.


我用的依然是Log 4J,几点建议就是：
1
log4j.rootLogger=debug, R
log4j.logger.org.apache.catalina=DEBUG, R
中的debug, DEBUG根据你的记录级别调整，我喜欢用error ERROR
2
log4j.appender.R.File=${catalina.home}/logs/tomcat.log
这个地方不需要人为修改
3
建议在系统环境变量增加：CATALINA_HOME一项配置以下Tomcat的安装目录




另外一篇：
习惯用log4j来配置log信息的输出。

新建log4j.properties，内容为

log4j.rootLogger=info,Console,R

log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
#log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p %c - %m%n
log4j.appender.Console.layout.ConversionPattern=%d{yy-MM-dd HH:mm:ss} %5p %c{1}:%L - %m%n

log4j.appender.R=org.apache.log4j.DailyRollingFileAppender
log4j.appender.R.File=${catalina.home}/logs/tomcat.log
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d{yyyy.MM.dd HH:mm:ss} %5p %c{1}(%L):  %m%n

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

最后四行是tomcat的信息，如果改为debug日志文件将十分庞大。

将这个文件放入${catalina.home}/common/classes下，再将log4j.jar和commons-logging.jar放入${catalina.home}/common/lib下，就可以在${catalina.home}/logs/下见到日志了。