如何在logback日志配置文件中配置相对路径

#相对路径

log_home=./infoLogs
log4j.rootLogger=info,stdout,R
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

log4j.appender.stdout.layout.ConversionPattern=[%t] (%F:%L) %d{yyyy-MM-dd HH:mm:ss} - %m%n

log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=[%d{yyyyMMdd HH:mm:ss}-%p][%F:%L][%t]-- %m%n
log4j.appender.R=org.apache.log4j.RollingFileAppender
log4j.appender.R.File=${log_home}/app.log
log4j.appender.R.MaxFileSize=1024KB
log4j.appender.R.MaxBackupIndex=10