log4j.properties文件的内容：
log4j.rootLogger=INFO,A1,R
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%c]-[%p] %m%n
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=/log_file.log
log4j.appender.R.MaxFileSize=1024KB
log4j.appender.R.MaxBackupIndex=1
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} [%c] [%p] - %m%n
放到web-inf目录下
使用方法：
import org.apache.log4j.*;
if (logger.isInfoEnabled()){
logger.info("Here is information from log4j");
}
