在tomcat启动的时候，出现这个警告：
log4j:WARN No appenders could be found for logger (org.apache.commons.digester.Digester.sax).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN No appenders could be found for logger (org.ajax4jsf.renderkit.ChameleonRenderKitFactory).
log4j:WARN Please initialize the log4j system properly.
解决办法，将log4j.properties放在web-inf\classes下，将 log4j.jar放在web-inf\lib下。