I can't for the life of me get an executable JAR f...

# announcements

[Kris Wong]

I can't for the life of me get an executable JAR for my kotlin project. I have tried adding an artifact to my project and specifying Main-Class in MANIFEST.MF, but still I get "no main manifest attribute" when running java -jar

[LeoColman]

Do you use Gradle? I usually just add the Shadow plugin and let it do the rest xD

[Kris Wong]

yes

[Kris Wong]

I can look into that

[LeoColman]

It embeds all the libraries in a big jar for you to execute

[Kris Wong]

yeah i've got that much working, so I can at least java -cp my.jar Main

[Kris Wong]

but I can't java -jar my.jar

[Big Chungus]

Here's how I've done it https://gitlab.com/mp.bootstrappers/kotlin-fullstack-mpp/blob/master/build.gradle.kts

It might be a bit outdated by now

[Big Chungus]

or this:

getByName("jar", Jar::class) {
      dependsOn("frontendJar", "backendJar")
      group = "package"
      manifest {
        attributes(
            mapOf(
                "Implementation-Title" to rootProject.name,
                "Implementation-Group" to rootProject.group,
                "Implementation-Version" to rootProject.version,
                "Timestamp" to System.currentTimeMillis(),
                "Main-Class" to mainClassName
            )
        )
      }
      val dependencies = configurations["backendRuntimeClasspath"].filter { it.name.endsWith(".jar") } +
          project.tasks["backendJar"].outputs.files +
          project.tasks["frontendJar"].outputs.files
      dependencies.forEach {
        if (it.isDirectory) from(it) else from(zipTree(it))
      }
      exclude("META-INF/*.RSA", "META-INF/*.SF", "META-INF/*.DSA")
      inputs.files(dependencies)
      outputs.file(archiveFile)
    }

[Kris Wong]

shadow seems to be what I am looking for, however it appears to use the configuration from the java plugin, and java is kind of ambiguous in the gradle script

[Kris Wong]

specifically it returns a type of JavaPluginExtension, which is very different than the plugin type itself

[Kris Wong]

public interface JavaPluginExtension {
    /**
     * Returns the source compatibility used for compiling Java sources.
     */
    JavaVersion getSourceCompatibility();

    /**
     * Sets the source compatibility used for compiling Java sources.
     *
     * @param value The value for the source compatibility
     */
    void setSourceCompatibility(JavaVersion value);

    /**
     * Returns the target compatibility used for compiling Java sources.
     */
    JavaVersion getTargetCompatibility();

    /**
     * Sets the target compatibility used for compiling Java sources.
     *
     * @param value The value for the target compatibility
     */
    void setTargetCompatibility(JavaVersion value);
}

[Kris Wong]

no manifest function

[Big Chungus]

I was facing the same issues myself with it, thus in the end I've decided to just do it manually

[Big Chungus]

It's quite easy too

[Big Chungus]

Dont forget to add Kt to your main class btw

[Big Chungus]

As in com.package.MainKt

[Kris Wong]

i've tried every permutation of adding main

[Big Chungus]

Also, if you could post a snippet of your error i could assist better

[Big Chungus]

I think i had some issues with manifest in the past too

[Kris Wong]

i see that the gradle block is actually supposed to be jar , not java, but that doesn't work either

[Big Chungus]

Are you able to post your gradle config for inspection? The one where you tried manual approach

[Kris Wong]

well, the jar creation is outside of the gradle file. it's an IDEA feature.

[Big Chungus]

Umm, why don't you just do that in gradle? Seems much easier

[Kris Wong]

because i need to create a fat jar... and it would have taken me a week to figure that out 😛

[Kris Wong]

i am going to give this shadow a try, i see how I can configure it

[Big Chungus]

If you can post your gradlefile i can write up a fatJar gradle task for you

[Kris Wong]

i appreciate that, but I would much prefer to leverage a plugin than maintain that myself

[Big Chungus]

No worries. It all comes down to preferences in the end

[Kris Wong]

shadow works 😃

[jimn]

-cp./target/lib/* with maven deps plugin (not sure how to do same with gradle) makes a simple painless footprint with no uberjar manifest collisions