How to change root logging level programmatically for Logback

java

logging

logback

configuration

byAnton Shumikhin·Jan 4, 2025

Switch logging levels in Logback as if you're flipping switches on a late-night coding spree! 👨‍💻💡

// Set root logger level to save your sanity (e.g., Level.INFO)
((LoggerContext) LoggerFactory.getILoggerFactory())
  .getLogger(Logger.ROOT_LOGGER_NAME).setLevel(Level.INFO);

Swap Level.INFO for your desired log level—Level.DEBUG if you're into mysteries or Level.ERROR if you like the thrill. This code snippet is the golden key 🔑 to configure the root log level in Logback.

Mini-glossary

LoggerContext: The underworld 🕳️ of all your logging contexts.
LoggerFactory: The factory 🏭 where all your loggers are crafted.
Logger.ROOT_LOGGER_NAME: Universal broadcaster 📢—everyone hears if you yell here.
setLevel(Level.INFO): Leveling up the logger to your current need.

Deep dive into log level manipulation

Direct modifications to the logging Gatekeeper

When a specific event occurs in your app and it requires you to be extra alert, updating the log level is as easy as changing your clothes.👕👖

Logger rootLogger = (Logger) LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME); // Find your ROOT_LOGGER
rootLogger.setLevel(Level.WARN); // Whisper, yells are so 2020!

Embracing real-time configurations

Configure Logback to conduct periodic scans of your config file, a habit even your dentist would be proud of: 🦷😁

<configuration scan="true" scanPeriod="30 seconds">
  ...
</configuration>

Switching log level gears based on application events

if (alienInvasionDetected()) { // 👽 When the extraordinary happens
  rootLogger.setLevel(Level.ERROR); // Shine the Bat-Signal 🦇💡
}

Discover advanced logging techniques

Context-centric logging with MDC

Be like Spiderman🕷️, act locally while thinking globally.

MDC.put("userId", "PeterParker");

Testing - because we are all humans

Favorite activity of developers after coding: testing loggers! And a way to verify we get what we expect with mockAppender.

rootLogger.addAppender(mockAppender);
// Logs emitted will now be caught by the mockAppender. Sneaky, isn't it? 🕵️‍♂️
rootLogger.detachAppender(mockAppender); // Always remember to clean up your mess

Scala and Logger setting - a perfect blend

For you Scala folks out there, this one's for you. Here's how you can elegantly set the logging level:

import org.slf4j.LoggerFactory
import ch.qos.logback.classic.{Level, Logger}
object LoggerConfigurer {
  def setRootLevel(level: Level): Unit = {
    val rootLogger = LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME).asInstanceOf[Logger]
    rootLogger.setLevel(level) // Fancy, isn't it? 🎩
  }
}