log4j logger标签中additivity属性
将logger中的 additivity 属性配置为 false，则这个logger不会将日志流反馈到root中。
可以达到以logger中配置的appender方式来输出日志而其他地方输出的目的，看配置：
< appender name = "DEMO" class = "com.XXXXX.RollingFileAppender" >
< param name = "file" value = "${loggingRoot}/xxx.log" />
< param name = "append" value = "true" />
< param name = "encoding" value = "GB2312" />
< param name = "threshold" value = "info" />
< param name = "MaxFileSize" value = "50MB" />
< param name = "MaxBackupIndex" value = "10" />
< layout class = "org.apache.log4j.PatternLayout" >
< param name = "ConversionPattern" value = "%d [%X{requestURIWithQueryString}] %-5p %c{2} - %m%n" />
</ layout >
</ appender >
< logger name = "XXXX.XXXX.XXXX" additivity = "false" >
< level value = "${loggingLevel}" />
< appender-ref ref = "DEMO" />
</ logger >root的作用是收集下面所有反馈上来的信息流并根据配置在root中appender进行输出，只要你在looger中配置了additivity="false"，就不会反馈到root中。
意味着不会重复输出！
log4j.additivity用法和例子
因为需要将packageOne和packageTwo的日志写入各自单独的文件，同时在总的日志中不出现packageOne和PackageTwo的日志。
可以使用log4j.additivity。因为log4j是层次的，如果没有log4j.additivity默认写入到packageOneFileAppender和packageTwoFileAppender的都会写入rootLogger的rootFileAppender
log4j.logger.com.demo.packageOone = INFO, packageOneFileAppender
log4j.additivity.com.demo.packageOne
= false
log4j.category.com.demo.packageTwo = INFO, packageTwoFileAppender
log4j.additivity.com.demo.packageTwo = false
log4j.rootLogger = INFO, rootFileAppender以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
