Apache Log4j API for Kotlin contains Kotlin-specific enhancements to the Log4j 2 API. This includes support for mixin interfaces and coroutine contexts.

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Apache Log4j 2 (Kotlin API)

Log4j Kotlin API is a Kotlin logging facade based on Apache Log4j API. Log4j Kotlin API provides Log4j Core 2.x as its default logging implementation, but this is not strictly required (e.g., this API can also be used with Logback or other Log4j 2 API provider implementations). Idiomatic Kotlin features are provided as an alternative to using the Log4j Java API.

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Users should refer to Maven, Ivy and Gradle Artifacts on the Log4j website for instructions on how to include Log4j into their project using their chosen build tool.

Using the Kotlin API is as simple as mixing in the Logging interface to your class. Example:

import org.apache.logging.log4j.kotlin.Logging

class MyClass: BaseClass, Logging {
    fun doStuff() {
        logger.info("Doing stuff")
    fun doStuffWithUser(user: User) {
        logger.info { "Doing stuff with ${user.name}." }

The Logging interface can also be mixed into object declarations, including companions. This is generally preferable over the previous approach as there is a single logger created for every instance of the class.

import org.apache.logging.log4j.kotlin.Logging

class MyClass: BaseClass {
    companion object : Logging
    // ...

Alternatively, a more traditional style can be used to instantiate a logger instance:

import org.apache.logging.log4j.kotlin

class MyClass: BaseClass {
    val logger = logger()
    // ...

The function logger() is an extension function on the Any type (or more specifically, any type T that extends Any).


The user guide for Log4j Kotlin API is available here.


The minimum requirements for Log4j Kotlin API are Java 8 and Kotlin 1.3.x. Log4j API is also required, though this is already specified as a transitive dependency for log4j-api-kotlin which is supported by common build systems like Maven, Gradle, SBT, and Ivy. A logging backend library such as Log4j Core, Logback, or java.util.logging is required at runtime for an application to configure the output of logging. Log4j Core version 2.x includes various plugins and configuration options which may require additional dependencies. See the Log4j manual for more details.

This library requires a dependency on kotlin-reflect in order to determine appropriate logger names from classes. When kotlinx-coroutines-core is available, this library provides a CoroutineThreadContext for supporting the ThreadContext API (and MDC/NDC APIs) in coroutines.

This library declares a provided scope dependency on Kotlin 1.3. This is to ensure that consumers of this library specify the proper Kotlin dependencies corresponding to the version of the Kotlin language in use and avoiding dependency conflicts.


Apache Log4j Kotlin API is distributed under the Apache License, version 2.0.


How to download Log4j Kotlin API, and how to use it from Maven, Ivy and Gradle. You can access the latest development snapshot by using the Maven repository https://repository.apache.org/snapshots, see Snapshot builds.

Issue Tracking

Issues, bugs, and feature requests should be submitted to the GitHub issues page for this project.

Pull request on GitHub are welcome; corresponding GitHub issues should be referenced in the PR.

Building From Source

Log4j Kotlin API requires Maven 3 and Java 8 to build. To install to your local Maven repository, execute the following:

mvn install


We love contributions! Take a look at our contributing page.