如何正确进行Log4j配置

Question

I am new to the Log4j framework and after reading some stuff i got some fare idea about logging mechanism, but still i have some doubt about the following properties.

log4j.category.com.cloud.sample=INFO, file, C
log4j.additivity.com.cloud.sample=true

log4j.appender.C=org.apache.log4j.ConsoleAppender
log4j.appender.C.Target=System.out
log4j.appender.C.ImmediateFlush=true
log4j.appender.C.layout=org.apache.log4j.PatternLayout
log4j.appender.C.layout.ConversionPattern=%-5p %d [%t] %m%n

#log4j.rootLogger=INFO, A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%d [%t] %-5p %c - %m%n

### direct messages to file ###
log4j.appender.file=org.apache.log4j.RollingFileAppender
log4j.appender.file.File=${catalina.home}/var/basic/logs/sample.log
log4j.appender.file.Append=true
log4j.appender.file.MaxFileSize=10MB
# mylog.log.10 \u307e\u3067\u4fdd\u6301
log4j.appender.file.MaxBackupIndex=50
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d %5p [%t] %c{1} - %m%n

log4j.rootLogger=INFO, C, file

In the first line of the above code contains two appenders(file, C) after that we will be having appender for both file and C. So as per my understanding logs will of category will be stored to Console and sample.log. Please let me know if i am wrong.

log4j.rootLogger=INFO, A1 and respective properties are not used right?

log4j.rootLogger=INFO, C, file: This line is about root logger, I think in my case it is not useful, because it is defined at the last line and there is no properties defined over here.

Please could any body confirm my understanding and suggest me if any changes required in the above configuration

Answer 1

The root logger resides at the top of the logger hierarchy. It is exceptional in three ways:

it always exists,
its level cannot be set to null
it cannot be retrieved by name.

The rootLogger is the father of all appenders. Each enabled logging request for a given logger will be forwarded to all the appenders in that logger as well as the appenders higher in the hierarchy (including rootLogger).