Kotlin: How to create a runnable jar? - kotlin

Question

I'm trying to create a runnable jar with Kotlin.
My gradle.build is this:
plugins {
id 'org.jetbrains.kotlin.jvm' version '1.3.11'
}
group 'com.github.dynamik'
version '1.0-SNAPSHOT'
apply plugin: 'application'
apply plugin: 'kotlin'
mainClassName = "interpreter.Repl"
repositories {
mavenCentral()
maven { setUrl("https://dl.bintray.com/hotkeytlt/maven") }
}
configurations {
ktlint
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
compile 'com.github.h0tk3y.betterParse:better-parse-jvm:0.4.0-alpha-3'
// https://mvnrepository.com/artifact/junit/junit
testCompile group: 'junit', name: 'junit', version: '4.4'
ktlint "com.github.shyiko:ktlint:0.31.0"
implementation 'com.github.ajalt:clikt:1.7.0'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.2.0'
}
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
run {
standardInput = System.in
}
jar {
manifest {
attributes 'Main-Class': 'interpreter.Repl'
}
}
(As it stands, when I do ./gradlew run, everything works as expected.)
I'm reading an article here on how to proceed, and it says to do: java -jar <MY_PROJECT_NAME>.jar.
I don't quite understand this -- where do we run this? I tried running it from my project root and I got an error:
Error: Unable to access jarfile <my_jarname>.jar

Answer 1

As of Gradle 5.4.1, a build.gradle.kts would need a section like this:
tasks.register<Jar>("uberJar") {
archiveClassifier.set("uber")
manifest {
attributes(
"Main-Class" to "mytest.AppKt",
"Implementation-Title" to "Gradle",
"Implementation-Version" to archiveVersion
)
}
from(sourceSets.main.get().output)
dependsOn(configurations.runtimeClasspath)
from({
configurations.runtimeClasspath.get().filter { it.name.endsWith("jar") }.map { zipTree(it) }
})
}

Answer 2

Ok, I figured it out :)
So, the way to create a jar is to go: ./gradlew build. This creates a jar in build/libs.
The problem is, when running that jar, one would run into an exception about java.lang.intrinsics because the kotlin stdlib hasn't been packed into the jar.
While there is a way to manually accomplish that, I found the easiest solution is to simply use the shadowjar plugin.
My build.gradle ended up looking like this:
buildscript {
repositories {
jcenter()
}
dependencies {
classpath 'com.github.jengelman.gradle.plugins:shadow:2.0.4'
}
}
plugins {
id 'org.jetbrains.kotlin.jvm' version '1.3.11'
}
group 'com.github.dynamik'
version '1.0-SNAPSHOT'
apply plugin: 'application'
apply plugin: 'kotlin'
apply plugin: 'java'
mainClassName = "interpreter.Repl"
repositories {
mavenCentral()
jcenter()
maven { setUrl("https://dl.bintray.com/hotkeytlt/maven") }
maven {
url = uri("https://plugins.gradle.org/m2/")
}
}
configurations {
ktlint
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
compile 'com.github.h0tk3y.betterParse:better-parse-jvm:0.4.0-alpha-3'
// https://mvnrepository.com/artifact/junit/junit
testCompile group: 'junit', name: 'junit', version: '4.4'
ktlint "com.github.shyiko:ktlint:0.31.0"
implementation 'com.github.ajalt:clikt:1.7.0'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.2.0'
}
apply plugin: 'com.github.johnrengelman.shadow'
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
run {
standardInput = System.in
}
jar {
manifest {
attributes 'Main-Class': 'interpreter.Repl'
}
}

Answer 3

When using a Kotlin main class you need to add a Kt at the end of the class name while referencing it on MANIFEST.
So, if your main class is called interpreter.Repl, use:
jar {
manifest {
attributes 'Main-Class': 'interpreter.ReplKt'
}
}
instead of
jar {
manifest {
attributes 'Main-Class': 'interpreter.Repl'
}
}