java - how to write to a text file using to log4j?

Question

I'm wondering how to convert the following code to output those lines into a text file, and not to standard output:

import org.apache.log4j.Logger; import org.apache.log4j.PropertyConfigurator;

public class HelloWorld {

    static final Logger logger = Logger.getLogger(HelloWorld.class);

    public static void main(String[] args) {
        PropertyConfigurator.configure("log4j.properties");
        logger.debug("Sample debug message");
        logger.info("Sample info message");
        logger.warn("Sample warn message");
        logger.error("Sample error message");
        logger.fatal("Sample fatal message");
    }
}

The properties file is :

log4j.rootLogger=DEBUG, CA
log4j.appender.CA=org.apache.log4j.ConsoleAppender
log4j.appender.CA.layout=org.apache.log4j.PatternLayout
log4j.appender.FA.layout.ConversionPattern=%m%n

Thanks.

Answer 1

Change the ConsoleAppender to a FileAppender.

I find the org.apache.log4j.RollingFileAppender to be useful. If you use this, you must add a property for the fileName and may want to set the maxFileSize as well. Here is an example (put these in the log4j.properties file):

log4j.appender.NotConsole=org.apache.log4j.RollingFileAppender
log4j.appender.NotConsole.fileName=/some/path/to/a/fileName.log
log4j.appender.NotConsole.maxFileSize=20MB

There are other appenders. DailyRollingFileAppender rolls based on time. FileAppender does not roll. If you use the RollingFileAppender, you will need to guess as to a good value for maxFileSize and then address the size at a future date if it is causing issues.