Tomcat 使用Log4j问题

    用上tomcat5.5，发现日志信息没有，出错了也找不着有用的信息.

    apache官方声明：

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

习惯用log4j来配置log信息的输出。

1、新建log4j.properties，内容为

### set log levels ###log4j.rootLogger=info,A,R ### 输出到控制台 A部分linux不加，否则日志打印两份， 若在window系统则加 ### log4j.appender.A=org.apache.log4j.ConsoleAppenderlog4j.appender.A.layout=org.apache.log4j.PatternLayoutlog4j.appender.A.layout.ConversionPattern=%p:\t%d{yy-MM-dd HH:mm} %c{1}:%L - %m%n ### 输出到日志文件,文件过大则重新生成一个 ###log4j.appender.R=org.apache.log4j.RollingFileAppenderlog4j.appender.R.layout=org.apache.log4j.PatternLayoutlog4j.appender.R.File=${catalina.home}/logs/catalina.outlog4j.appender.R.MaxFileSize = 30MBlog4j.appender.R.MaxBackupIndex = 50log4j.appender.R.layout.ConversionPattern=%p:\t%d{yy-MM-dd HH:mm} %c{1}_%L - %m%n#加了以下这一行会打印两份。#log4j.logger.org.apache=info, Rlog4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=info, R log4j.logger.org.apache.catalina.core=info, Rlog4j.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，。

#log4j.logger.org.apache=info, R

这句保留的话，catalina.out将会打印两次，切记！

2、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。