Lightweight logging framework for Kotlin. A convenient and performant logging library wrapping slf4j with Kotlin extensions.

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• Call log methods, without checking whether the respective log level is enabled:

logger.debug { "Some $expensive message!" }

Behind the scenes the expensive message do not get evaluated if debug is not enabled:

if (logger.isDebugEnabled) logger.debug("Some $expensive message!")

• Define the logger, without explicitly specifiying the class name:

val logger = KotlinLogging.logger {}

or

companion object: KLogging()

Behind the scenes val logger will be created in the class, with the class/file name:

val logger = LoggerFactory.getLogger("class name")

• Log exceptions in a Kotlin-style

logger.error(exception) { "a $fancy message about the $exception" }

val logger = KotlinLogging.logger {} 
class FooWithLogging {
    val message = "world"
    fun bar() {
        logger.info { "hello $message" }
    }
}

An Android example project with kotlin logging can be found in kotlin-logging-example-android.

Important note: kotlin-logging depends on slf4j-api. In runtime, it is also required to depend on a logging implementation. More details here.

<dependency>
  <groupId>io.github.microutils</groupId>
  <artifactId>kotlin-logging</artifactId>
  <version>1.4.1</version>
</dependency>

See full example in kotlin-logging-example-maven.

compile 'io.github.microutils:kotlin-logging:1.4.1'

Or alternatively, download jar from github or bintray or maven-central.

After seeing many questions like Idiomatic way of logging in Kotlin and Best practices for loggers, It seems like there should be a standard for logging and obtaining a logger in kotlin. kotlin-logging provide a wrapper for slf4j api to be used by kotlin classes with the following advantages:

• No need to write the logger and class name or logger name boileplates.
• A straight forward way to log messages with lazy-evaluated string using lambda expression {}.
• All previous slf4j implementation still can be used.

• Why not use plain slf4j? kotlin-logging has better native kotlin support. It adds more functionality and enable less boilerplates.
• Is all slf4j implementation supported (Markers, params, etc')? Yes, KLogger inherits Logger and all methods are supported.
• Is location logging possible? Yes, location awerness was added in kotlin-logging 1.4.

• See wiki for more examples.

• Open an issue here: https://github.com/MicroUtils/kotlin-logging/issues
• Ask a question in StackOverflow with kotlin-logging tag.
• Chat on Slack channel: https://kotlinlang.slack.com/messages/kotlin-logging

• kotlin-logging is hosted on bintray and maven central.
• https://medium.com/@OhadShai/logging-in-kotlin-95a4e76388f2
• kotlin-logging vs AnkoLogger for Android
• How kotlin-logging was published

• Pull requests are welcome!