Log4J2 - assigning file appender filename at runtime

Question

I have a log4j2.xml config file in the class path. One of the appenders is a File appender, and I would like to set the target file name at run time in the Java application

Answer 1

I know this topic is old, but the answers did not really suit me. Here is a function which allows you to reconfigure an existing Appender at runtime:

static void updateLogger(String file_name, String appender_name, String package_name){
LoggerContext context = (LoggerContext) LogManager.getContext(false);
    Configuration configuration = context.getConfiguration();
    Layout old_layout = configuration.getAppender(appender_name).getLayout();

    //delete old appender/logger
    configuration.getAppender(appender_name).stop();
    configuration.removeLogger(package_name);

    //create new appender/logger
    LoggerConfig loggerConfig = new LoggerConfig(package_name, Level.INFO, false);
    FileAppender appender = FileAppender.createAppender(file_name, "false", "false", appender_name, "true", "true", "true",
            "8192", old_layout, null, "false", "", configuration);
    appender.start();
    loggerConfig.addAppender(appender, Level.INFO, null);
    configuration.addLogger(package_name, loggerConfig);

    context.updateLoggers();
}

You can specify a file name, the name of your appender and the package name which you want to log.

Example Logger:

Can be reconfigured calling like this:

updateLogger("log/api_new.log", "fileWriter_api", "my.package");