Hominem quaero

log4j без конфигов

Создание логгера log4j в виде объекта.

package your.package;

import org.apache.log4j.*;
import java.io.IOException;

public class LoggerHelper {

    public Logger log;

    public LoggerHelper(String loggerName, String logFileName, String conversionPattern, String logLevel) {
        PatternLayout layout = new PatternLayout();
        layout.setConversionPattern(conversionPattern);

        RollingFileAppender appender;
        try {
            appender = new RollingFileAppender(layout, logFileName);
            appender.setName(loggerName);
            appender.setFile(logFileName);
            appender.setMaxFileSize("1MB");

            layout.activateOptions();
            appender.activateOptions();
            BasicConfigurator.configure();

            log = LogManager.getLogger(loggerName);
            Logger.getRootLogger().addAppender(appender);
            Logger.getRootLogger().setLevel(getLevel(logLevel));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void close() {
        log.getLoggerRepository().shutdown();
    }

    private Level getLevel(String level) {
        Level loggerLevel;
        switch (level) {
            case "Info":
                loggerLevel = Level.INFO;
                break;
            case "Debug":
                loggerLevel = Level.DEBUG;
                break;
            default:
                loggerLevel = Level.INFO;
                break;
        }
        return loggerLevel;
    }
}

Использование:

String loggerName = "loggerName";
String logName = @"C:\someFolder\logname.log";
LoggerHelper logger = new LoggerHelper(loggerName, logName, "%d  %-5p %m%n", "Debug");
logger.log.info("Hello World!");
logger.log.debug("Hello World!");
//
logger.close();

Содержимое лога:

2018-04-22 13:23:29,575  INFO  Hello World!
2018-04-22 13:23:29,575  DEBUG Hello World!