Log4J API not printing messages in the java program

Question

I am trying to implement Log4J API in my java project. To do that, I have created a properties as shown in the image below (highlighted in yellow): Project Structure Image

These are the properties I set in the file:

# TRACE < DEBUG < INFO < WARN < FATAL
log4j.rootLogger=TRACE, DEBUG, INFO, file

# Console
# log4j.appender.toConsole=org.apache.log4j.ConsoleAppender
# log4j.appender.toConsole.layout=org.apache.log4j.PatternLayout
# log4j.appender.toConsole.layout.ConversionPatter=%d{HH:mm:ss} %5p [%t] - $c.%M - %m%n

# Redirecting log messages to console
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

I declared the LOGGER object in my class as following:

import org.apache.log4j.Level;
import org.apache.log4j.Logger;
public class Credits{

    Logger LOGGER = null;
    public Credits(String sources) {
        LOGGER = Logger.getLogger(ChunkRecon.class.getName());
        LOGGER.setLevel(Level.DEBUG);
        String  creditNames = "select tablename, creditNumbers, credit_type from schema.table where credit_type in ("sources")";
        LOGGER.debug("This is a debug message");
        system.out.println("This message is from println");
    }
}

In the output, I see the message from sysout: This message is from println but not the debug message.

Could anyone let me know what is the mistake I am doing here ?

ilinykhma · Answer 1 · 2019-02-11T11:31:33.090

Try to rename your loggerproperties to log4j.properties and check it is in classpath. Another problem with rootLogger, see explanation here

Also Logger is usually used as static variable. For example:

public class Credits {

    private static final Logger logger = Logger.getLogger(Credits.class);

    public Credits(String sources) {
        logger.setLevel(Level.DEBUG);
        logger.debug("This is a debug message");

        System.out.println("This message is from println");
    }
}

log4j.properties

log4j.rootLogger=debug, 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

If I make it static or private static, the compiler says: Illegal modifier for parameter LOGGER; only final is permitted. Also changing file name wouldn't have any impact. — Torque, Feb 11 '19 at 11:21

Haripriya · Answer 2 · 2019-02-11T12:43:40.470

Your log4j.rootLogger declaration seems incorrect. Try as -

log4j.rootLogger=TRACE,stdout,file
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.file=org.apache.log4j.RollingFileAppender

If you only want the logs on console then remove file logging fully.

log4j.rootLogger=TRACE,stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender

Refer section Configuring loggers from JavaDoc.
The syntax for configuring the root logger is:

log4j.rootLogger=[level], appenderName, appenderName, ...

Log4J API not printing messages in the java program

2 Answers2