how to log4j.properties configuration file that the error appears on a text file and not in the consol
This is standard log4j - not really anything to do with KonaKart....
Nevertheless, you could use something like this:
// KonaKart Appender
log4j.appender.KonaKartAppender=org.apache.log4j.FileAppender
log4j.appender.KonaKartAppender.layout=org.apache.log4j.PatternLayout
log4j.appender.KonaKartAppender.layout.ConversionPattern=%d{dd-MMM HH:mm:ss} %-5p (%F:%M:%L) %m%n
log4j.appender.KonaKartAppender.file=../logs/KonaKart.log
Remember to add the "KonaKartAppender" to the log4j.rootLogger definition as well.