Different Log Levels in SLF4j

There are different ways to log messages, in order of fatality:

1. ERROR
2. WARN
3. INFO
4. DEBUG
5. TRACE

Common levels

Level	Description
ERROR	Other runtime errors or unexpected conditions. Expect these to be immediately visible on a status console.
WARN	O
INFO	Interesting runtime events (startup/shutdown). Expect these to be immediately visible on a console, so be conservative and keep to a minimum.
DEBUG	detailed information on the flow through the system. Expect these to be written to logs only.
TRACE	more detailed information. Expect these to be written to logs only.

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

 

public class Log4jExample {

 

    private static Logger logger = LoggerFactory.getLogger(Log4jExample.class);

 

    public static void main(String[] args) {

        logger.trace("Trace log message");       

  logger.debug("Debug log message");

        logger.info("Info log message");

        logger.warn("Warning log message");        

logger.error("Error log message");

    }

}

if INFO is set then output:

2018-06-16 17:02:13 INFO  Info log message

2018-06-16 17:02:13 WARN Warning log message

2018-06-16 17:02:13 ERROR Error log message




if trace is set:

2018-06-16 17:02:13 TRACE Trace log message

2018-06-16 17:02:13 DEBUG Debug log message

2018-06-16 17:02:13 INFO  Info log message

2018-06-16 17:02:13 WARN Warning log message

2018-06-16 17:02:13 ERROR Error log message