Java : How to use a logger to log from multiple classes into a same file?

Question

I have a main class say class A where :

public class A {
    someMethod(){
        log.debug("inside some method in class A");
    }
}

And then class B where :

public class B {
    someOtherMethod(){
        log.debug("inside some other method in class B");
    }
}

Now how do I use loggers here, i.e., to log from both these classes and log into a common log file? What should be configuration of the properties file?

Answer 1

if you are using log4j, you can add a config.properties file to your resources:

# Root logger option
log4j.rootLogger=INFO, file, stdout

# Direct log messages to a log file
log4j.appender.file=org.apache.log4j.RollingFileAppender
# this is the ouput file path and name
log4j.appender.file.File=filename.log
log4j.appender.file.MaxFileSize=10MB
log4j.appender.file.MaxBackupIndex=10
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

# Direct log messages to stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L - %m%n

Then you can use like this:

import org.apache.log4j.Logger;

public class A {
    Logger log= Logger.getLogger(A.class);
    someMethod(){
       log.debug("inside some method in class A");
    }

public class B {
    Logger log= Logger.getLogger(B.class);
    someOtherMethod(){
        log.debug("inside some other method in class B");
    }
}