How to configure slf4j-simple

Question

api 1 7 and slf4j-simple as implementation  I just can t find how to configure the logging level with this combination    Can anyone help out

User · Answer

You can programatically change it by setting the system property:

public class App {

    public static void main(String[] args) {

        System.setProperty(org.slf4j.impl.SimpleLogger.DEFAULT_LOG_LEVEL_KEY, "TRACE");

        final org.slf4j.Logger log = LoggerFactory.getLogger(App.class);

        log.trace("trace");
        log.debug("debug");
        log.info("info");
        log.warn("warning");
        log.error("error");

    }
}

The log levels are ERROR > WARN > INFO > DEBUG > TRACE.

Please note that once the logger is created the log level can't be changed. If you need to dynamically change the logging level you might want to use log4j with SLF4J.

User · Answer

It s either through system property   -Dorg slf4j simpleLogger defaultLogLevel debug   or simplelogger properties file on the classpath  see http   www slf4j org api org slf4j impl SimpleLogger html for details

User · Answer

This is a sample simplelogger properties which you can place on the classpath  uncomment the properties you wish to use      SLF4J s SimpleLogger configuration file   Simple implementation of Logger that sends all enabled log messages  for all defined loggers  to System err     Default logging detail level for all instances of SimpleLogger    Must be one of   trace    debug    info    warn   or  error      If not specified  defaults to  info    org slf4j simpleLogger defaultLogLevel info    Logging detail level for a SimpleLogger instance named  xxxxx     Must be one of   trace    debug    info    warn   or  error      If not specified  the default logging detail level is used   org slf4j simpleLogger log xxxxx     Set to true if you want the current date and time to be included in output messages    Default is false  and will output the number of milliseconds elapsed since startup   org slf4j simpleLogger showDateTime false    The date and time format to be used in the output messages    The pattern describing the date and time format is the same that is used in java text SimpleDateFormat    If the format is not specified or is invalid  the default format is used    The default format is yyyy-MM-dd HH mm ss SSS Z   org slf4j simpleLogger dateTimeFormat yyyy-MM-dd HH mm ss SSS Z    Set to true if you want to output the current thread name    Defaults to true   org slf4j simpleLogger showThreadName true    Set to true if you want the Logger instance name to be included in output messages    Defaults to true   org slf4j simpleLogger showLogName true    Set to true if you want the last component of the name to be included in output messages    Defaults to false   org slf4j simpleLogger showShortLogName false

User · Answer

I noticed that Eemuli said that you can t change the log level after they are created - and while that might be the design  it isn t entirely true   I ran into a situation where I was using a library that logged to slf4j - and I was using the library while writing a maven mojo plugin   Maven uses a  hacked  version of the slf4j SimpleLogger  and I was unable to get my plugin code to reroute its logging to something like log4j  which I could control   And I can t change the maven logging config   So  to quiet down some noisy info messages  I found I could use reflection like this  to futz with the SimpleLogger at runtime   import org slf4j Logger  import org slf4j LoggerFactory  import org slf4j spi LocationAwareLogger      try               Logger l   LoggerFactory getLogger  full classname of noisy logger       This is actually a MavenSimpleLogger  but due to various classloader issues  can t work with the directly          Field f   l getClass   getSuperclass   getDeclaredField  currentLogLevel            f setAccessible true           f set l  LocationAwareLogger WARN INT             catch  Exception e                getLog   warn  Failed to reset the log level of     loggerName      it will continue being noisy    e           Of course  note  this isn t a very stable   reliable solution    as it will break the next time the maven folks change their logger

[java] How to configure slf4j-simple

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