proper way to run kotlin application from gradle task

Question

I've got simple script

package com.lapots.game.journey.ims.example


fun main(args: Array<String>) {
    println("Hello, world!")
}

And here is gradle task

task runExample(type: JavaExec) {
    main ='com.lapots.game.journey.ims.example.Example'
    classpath = sourceSets.main.runtimeClasspath
}

But when I try to run task gradle runExample I get error

Error: Could not find or load main class com.lapots.game.journey.ims.example.Example

What is the proper way to run application?

Possible duplicate of [how to run compiled class file in Kotlin?](http://stackoverflow.com/questions/9355690/how-to-run-compiled-class-file-in-kotlin) — Jayson Minard, Sep 19 '16 at 14:58
There is a section on using Gradle application plugin to run a Kotlin app: http://stackoverflow.com/a/26402542/3679676 ... or did you need it to run as-if it is a task in some other way? But that answer could also give you the clues you need. — Jayson Minard, Sep 19 '16 at 14:59

score 21 · Accepted Answer · edited May 23 '17 at 10:30

21

Thanks to the link how to run compiled class file in Kotlin? provided by @JaysonMinard that main

@file:JvmName("Example")

package com.lapots.game.journey.ims.example


fun main(args: Array<String>) {
    print("executable!")
}

and that task

task runExample(type: JavaExec) {
    main = 'com.lapots.game.journey.ims.example.Example'
    classpath = sourceSets.main.runtimeClasspath
}

did the trick

edited May 23 '17 at 10:30

Community

1
1

answered Sep 19 '16 at 17:53

lapots

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Is there a way to get runtimeClasspath for apps with android application plugin? – Tamim Attafi Feb 24 '21 at 12:41
how to pass arguments to the main function? – George Shalvashvili Aug 06 '21 at 10:47

score 14 · Answer 2 · edited Feb 01 '22 at 12:02

14

You can also use gradle application plugin for this.

// example.kt
package com.lapots.game.journey.ims.example

fun main(args: Array<String>) {
    print("executable!")
}

add this to your build.gradle

// build.gradle
apply plugin: "application"
mainClassName = 'com.lapots.game.journey.ims.example.ExampleKt'

Then run your application as follows.

./gradlew run

edited Feb 01 '22 at 12:02

Egor Neliuba

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answered Feb 21 '18 at 11:37

Subash

7,098
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2

For someone having the same stupid problem as me: it should be `apply plugin: "application"` (note the `:` here!) – Michel Dec 06 '19 at 10:44
it appears the colon is not in the answer. – Nailuj29 Jan 13 '21 at 17:02

Holger Brandl · Answer 3 · 2018-08-27T13:21:14.233

In case you're using a Kotlin buildfile build.gradle.kts you would need to do

apply {
    plugin("kotlin")
    plugin("application")
}    

configure<ApplicationPluginConvention> {
    mainClassName = "my.cool.App"
}

If you apply the application plugin using the plugins {} block instead you could make it simpler:

plugins {
    application
}

application {
    mainClassName = "my.cool.App"
}

For details see https://github.com/gradle/kotlin-dsl/blob/master/doc/getting-started/Configuring-Plugins.md

score 6 · Answer 4 · answered Jun 10 '20 at 15:13

6

For build.gradle.kts users

main file:

package com.foo.game.journey.ims.example


fun main(args: Array<String>) {
    println("Hello, world!")
}

build.gradle.kts file:

plugins {
    application
    kotlin("jvm") version "1.3.72" // <-- your kotlin version here
}

application {
    mainClassName = "com.lapots.game.journey.ims.example.ExampleKt"
}

...

And run with the following command:

./gradlew run

answered Jun 10 '20 at 15:13

Lukas Kirner

3,989
6
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this, rather than the `apply { _plugin_}` is what jetbrains is now pushing. – BobHy Nov 03 '22 at 02:09

score 5 · Answer 5 · answered Apr 26 '20 at 02:41

5

I found another way from the @lapots answer.

In your example.kt:

@file:JvmName("Example")

package your.organization.example

fun main(string: Array<String>) {
    println("Yay! I'm running!")
}

Then in your build.gradle.kts:

plugins {
    kotlin("jvm") version "1.3.72"
    application
}

application {
    mainClassName = "your.organization.example.Example"
}

answered Apr 26 '20 at 02:41

Jerv Norsk

51
1
2

Thank you for that post, really helpful :) Configuration is nice and clean :) – Hunter_71 May 04 '20 at 21:13

score 0 · Answer 6 · answered Aug 06 '21 at 11:02

it is possible to do it without adding package name. Run your app with the green play icon and it should show the main class name at the end of the command it runs.

inside build.gradle add className and application like this

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.5.10'
    id 'application'
}

mainClassName = 'AppKt'
...

now you can do ./gradlew run and to pass arguments also add --args='foo --bar'

proper way to run kotlin application from gradle task

6 Answers6

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