Question

s2sh框架，中加入log4j架包，在src下有log4j.properties文件，没有在web.xml里配置它，但为什么就会自动

输出日志信息，log4j是如何进行初始化的啊？

Answer 1

1.将log4j-1.2.14.jar加入你的项目中；
2.在src/下创建log4j.properties|log4j.xml文件；
3.在web.xml中配置log4j的信息，如下：
<context-param>
<param-name>log4jConfigLocation</param-name>
<param-value>/WEB-INF/classes/log4j.properties</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>
</listener>
4.在项目webroot下创建你想要保存日志文件的文件夹及文件，如webroot/logs/web_app.log；
具体log4j.properties文件，给你一个示例吧，如下:
log4j.rootLogger=INFO, stdout, logfile

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
#log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n
log4j.appender.stdout.layout.ConversionPattern=- %m%n

log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.File=$/logs/webapp.log
log4j.appender.logfile.MaxFileSize=512KB
# Keep three backup files.
log4j.appender.logfile.MaxBackupIndex=3
# Pattern to output: date priority [category] - message
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

log4j.logger.com.opensymphony.xwork2=ERROR

# Control logging for other open source packages
log4j.logger.org.springframework=ERROR
log4j.logger.org.quartz=ERROR
log4j.logger.net.sf.ehcache=ERROR
log4j.logger.net.sf.navigator=ERROR
log4j.logger.org.apache.commons=ERROR
log4j.logger.org.apache.struts=ERROR

# Struts OgnlUtil issues unimportant warnings
log4j.logger.com.opensymphony.xwork2.util.OgnlUtil=error
log4j.logger.com.opensymphony.xwork2.ognl.OgnlValueStack=error
具体写法可根据自己的项目进行配置。