log4j将日志写入任意名字的文件中，支持动态写入

log4j.logger.presentOperatorLog=DEBUG, stdout, ilog  #既输出到控制台，也写入文件
log4j.additivity.presentOperatorLog = false  #日志不输出到父日志中，既rootLogger中
log4j.appender.ilog=org.apache.log4j.FileAppender
log4j.appender.ilog.File=/temp/test.log
log4j.appender.ilog.layout=org.apache.log4j.PatternLayout
#log4j.appender.ilog.layout.ConversionPattern=%d %p [%c] - %m%n
log4j.appender.ilog.layout.ConversionPattern=%d{yyyy-mm-dd HH:mm:ss} | %m

private static Logger log = Logger.getLogger("presentOperatorLog"); //这里的presentOperatorLog就是上面定义的log4j.logger.presentOperatorLog

Appender appender = Logger.getLogger("presentOperatorLog").getAppender("ilog");
if(appender instanceof FileAppender){
FileAppender fappender = (FileAppender) appender;
Date dt = new Date();
SimpleDateFormat sf = new SimpleDateFormat("yyyymmddhhmmss");
String nowDate = sf.format(dt);

fappender.setFile("E:/" + nowDate + ".log");//新日志文件的文件名:"E:/" + nowDate + ".log"
fappender.activateOptions();  //启用新的日志文件
}
log.debug("you got it man");