Is it possible to use Lombok with Kotlin?

Question

I have a Kotlin Gradle project. I added Lombok as a dependency and also registered it with kapt

compileOnly("org.projectlombok:lombok:$lombokVersion")
kapt("org.projectlombok:lombok:$lombokVersion")

I would like to use the @Slf4j annotation for automatic logger generation. It works for Java classes but not for the Kotlin ones.

Is using Kotlin and Lombok together even possible as of now? If I annotate a Kotlin class with @Slf4j and use log inside it I get

Unresolved reference: log

Evidently no annotation processing is applied.

If its just for logging you may want to check https://discuss.kotlinlang.org/t/best-practices-for-loggers/226/9 — Emanuel, Sep 03 '17 at 21:22
Does this answer your question? [Kotlin doesn't see Java Lombok accessors?](https://stackoverflow.com/questions/35517325/kotlin-doesnt-see-java-lombok-accessors) — knittl, Oct 04 '22 at 09:42

score 23 · Answer 1 · answered Nov 03 '17 at 15:10

Lombok does not run on your source code, but on the AST. Anyway, it is an annotation processor that is run at compile-time by the Java compiler. The Kotlin compiler does not use these annotation processors. See also the answer https://stackoverflow.com/a/35530223/2621917 straight from the horse’s mouth.

YetAnotherMatt · Answer 2 · 2022-07-19T12:00:16.837

10

If all you want to use Lombok for is @Slf4j, then I'd suggest using kotlin-logging instead: https://github.com/MicroUtils/kotlin-logging

It's a simple wrapper around slf4j, so instead of annotating your class with @Slf4j, you use:

// Place definition above class declaration to make field static
private val logger = KotlinLogging.logger {}
// ...

logger.debug { "A message only logged if debug is enabled. With $variable support." }

edited Jul 19 '22 at 12:00

answered Sep 30 '18 at 15:12

YetAnotherMatt

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can you please give the reason why kotling logging is better> – taegyun kim Jul 13 '22 at 04:44
3

@taegyunkim I wouldn't argue that it's _better_, just that Lombok isn't available in Kotlin and KotlinLogging is a nice, simple, wrapper around Slf4j. – YetAnotherMatt Jul 19 '22 at 12:02
Oh it was a silly question. thx – taegyun kim Jul 20 '22 at 08:21

score 10 · Accepted Answer · answered Nov 23 '18 at 03:27

10

You cannot use annotation @Slf4j, but manually create its object in the class required.

Refer https://www.reddit.com/r/Kotlin/comments/8gbiul/slf4j_loggers_in_3_ways/

answered Nov 23 '18 at 03:27

Sahil Chhabra

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score 3 · Answer 4 · answered Dec 29 '22 at 11:18

Lombok's builder annotation support has been added to kotlin 1.8 as of late December 2022.

You can learn how to configure the plugin here.

In Short, add

plugins {
    id 'org.jetbrains.kotlin.plugin.lombok' version '1.8.0'
    id 'io.freefair.lombok' version '5.3.0'
}

to your Groovy/Gradle files, and/or take a look at the sample project.

score 1 · Answer 5 · answered Nov 03 '17 at 15:15

1

It's not supported and, by the looks of things, it isn't going to be.

answered Nov 03 '17 at 15:15

Michael

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score 1 · Answer 6 · answered Oct 04 '22 at 09:37

1

from kotlin 1.7.20 with K2 compiler it is possible.

https://kotlinlang.org/docs/whatsnew1720.html#support-for-kotlin-k2-compiler-plugins

answered Oct 04 '22 at 09:37

Никулин Данил

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score 0 · Answer 7 · answered Dec 14 '19 at 12:55

0

For logging the best I could do - because @Slf4j did not work - was like creating abstract log class like:

package org.example

import org.slf4j.LoggerFactory
import org.slf4j.Logger

abstract class Log {
    val log: Logger = LoggerFactory.getLogger(this.javaClass)
}

and usage:

package org.example

class MyClass { 
    companion object : Log() {}
    @Test
    fun someFun() {
        log.info("Logging info")
    }
}

answered Dec 14 '19 at 12:55

pirho

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@Michael it is not per instance since the companion object inherits from Log, but what I don't like is that you can't use this solution if you actually need to inherit from another class – Osman Oct 11 '22 at 14:52
1

@Osman A misunderstanding of the semantics of a companion object. My bad, thanks for the correction. – Michael Oct 11 '22 at 16:31

score -1 · Answer 8 · answered Sep 03 '17 at 21:17

-1

I can't see how it would work without additional support from the lombok team. Lombok is based on annotation processing so it runs during compilation time and runs on your source code, so I guess it assumes Java's syntax.

answered Sep 03 '17 at 21:17

Eyal

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Lombok doesn't run directly on your source code; rather, it exploits the Java compiler's built-in support for compile-time annotation processors. – ruakh Sep 03 '17 at 21:19
If I'm not mistaken, some of the advanced features of Lombok actually need access to the Java sources. – hotkey Sep 03 '17 at 22:03
AFAIK Lombok runs at compile-time. So it has access to your source code. It also uses some techniques to modify the generated AST – Alberto S. Sep 04 '17 at 06:26

Is it possible to use Lombok with Kotlin?

8 Answers8

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