RanZilber RanZilber - 1 month ago 6
Java Question

how to write to a text file using to log4j?

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.

DwB DwB
Answer

Change the ConsoleAppender to a FileAppender. One file appender that I find useful is org.apache.log4j.RollingFileAppender. You will have to 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, will have to make a guess as to a good value for maxFileSize and then address the size at a future date if it is causing issues.

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