Kotlin/JVM Inline Logging

Powered by SLF4J, fully inlined, and say goodbye to lambda object creation 😲

Prerequisites

• Java 8+
• Kotlin 1.5.0+

Features

• Fully inlined SLF4J logger
• lazily create log message without creating lambda object (because everything is inlined 😋)
• only showing lazy logging methods on your IDE (e.g. showing logger.info {} on your auto-complete hint instead of logger.info())

How to import

Check JitPack to see how to import

How to use

Simply add

private val logger = KInlineLogging.logger()

to anywhere you want and enjoy logging 😁

For example:

private val logger = KInlineLogging.logger() // an instance of KInlineLogger, which is a value class of SLF4J Logger

class MainApp {
  fun start() {
    logger.info { "an info msg" }
    val exception = SomeException()
    logger.debug(exception) { "a debug msg with exception $exception" }
  }
}

Under the hook, this should be compiled as:

private val logger: Logger = LoggerFactory.getLogger(
  KInlineLoggerNameResolver.fixName(MethodHandles.lookup().lookupClass())
) // A SLF4J Logger, not the KInlineLogger 😯

class MainApp {
  fun start() {
    if (logger.isInfoEnabled()){
      logger.info("an info msg") // no lambda object created 😊
    }
    val exception = SomeException()
    if (logger.isDebugEnabled()){
      // notice that this string creation will not happen if the debug level is not enabled
      logger.debug("a debug msg with exception $exception", exception) 
    } 
  }
}

Q: Can you support multi-platform?

A: Sorry, I am not supporting it, but you can just grab the only two source files in this library and modify it to suit your needs.