Kotlin Could not find or load main class

Question

I'm trying to build a jar from a kotlin app using intelliJ idea, everything works from intellij, it's able to run kotlin files with the main method, however after building the jar with gradle jar I get:

java -cp build/libs/sensorPreprocessor-1.0-SNAPSHOT.jar co.myapp.sensorPreprocessor.MqttPollerKt
Error: Could not find or load main class co.myapp.sensorPreprocessor.MqttPollerKt

my build.gradle is this:

plugins {
    id 'org.jetbrains.kotlin.jvm' version '1.3.31'
    id "com.commercehub.gradle.plugin.avro" version '0.16.0'
}

apply plugin: 'kotlin'
apply plugin: 'application'
mainClassName = 'co.myapp.sensorPreprocessor.MqttPollerKt'

group 'co.myapp'
version '1.0-SNAPSHOT'

repositories {
    mavenCentral()
    jcenter()
    maven {
        url  "https://dl.bintray.com/cbeust/maven"
    }
    maven {
        url  "http://packages.confluent.io/maven/"
    }
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
    compile "org.jetbrains.kotlin:kotlin-reflect:1.3.31"
    testCompile group: 'junit', name: 'junit', version: '4.12'

    compile group: 'org.apache.kafka', name: 'kafka-streams', version: '2.2.0'
    compile group: 'com.igormaznitsa', name: 'jbbp', version: '1.4.1'
    compile group: 'software.amazon.awssdk', name: 'sqs', version: '2.5.45'
    compile group: 'com.amazonaws', name: 'aws-iot-device-sdk-java', version: '1.3.0'
    compile group: 'com.amazonaws', name: 'aws-iot-device-sdk-java-samples', version: '1.3.0'
    compile group: 'com.beust', name: 'klaxon', version: '5.0.5'
    compile group: 'org.apache.kafka', name: 'kafka-clients', version: '2.2.0'
    compile group: 'io.confluent', name: 'kafka-avro-serializer', version: '5.2.1'
    compile group: 'io.confluent', name: 'kafka-streams-avro-serde', version: '5.2.1'
    compile group: 'io.confluent', name: 'monitoring-interceptors', version: '5.2.1'
    compile group: 'org.apache.avro', name: 'avro', version: '1.9.0'
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

jar {
    manifest {
        attributes 'Main-Class': 'co.myapp.sensorPreprocessor.MqttPollerKt'
    }

    from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
}

my main file is this:

package co.myapp.sensorPreprocessor

import software.amazon.awssdk.services.sqs.model.Message as AwsSqsMessage
....


class MqttPoller {
    companion object {
        @JvmStatic fun main(args: Array<String>) {
            start()
        }

        fun start() {
            ...
        }
    }
}

class MessagesTopic(topic: String, qos: AWSIotQos, private val kafkaProducer: KafkaProducer<String, SensorData>) : AWSIotTopic(topic, qos) {
    override fun onMessage(message: AWSIotMessage?) {
        ....
    }
}


fun main() {
    MqttPoller.start()
}

I've tried both co.myapp.sensorPreprocessor.MqttPollerKt and co.myapp.sensorPreprocessor.MqttPoller with the same results. If after I type java -cp JAR_PATH <tab> I try to autocomplete I can see it autocompletes with my class names, but still it doesn't work.

If I try to use javap it also shows the class:

➜  iot-services-sensor-preprocessor git:(master) ✗ javap -cp build/libs/sensorPreprocessor-1.0-SNAPSHOT.jar co.myapp.sensorPreprocessor.MqttPollerKt
Compiled from "MqttPoller.kt"
public final class co.myapp.sensorPreprocessor.MqttPollerKt {
  public static final void main();
  public static void main(java.lang.String[]);
}
➜  iot-services-sensor-preprocessor git:(master) ✗ javap -verbose -cp build/libs/sensorPreprocessor-1.0-SNAPSHOT.jar co.myapp.sensorPreprocessor.MqttPollerKt
Classfile jar:file:///Users/alex/Projects/myapp/build/libs/sensorPreprocessor-1.0-SNAPSHOT.jar!/co/myapp/sensorPreprocessor/MqttPollerKt.class
  Last modified May 21, 2019; size 754 bytes
  MD5 checksum 52febc7a2f38ef786ded2198193827b3
  Compiled from "MqttPoller.kt"
public final class co.myapp.sensorPreprocessor.MqttPollerKt
  minor version: 0
  major version: 52
  flags: (0x0031) ACC_PUBLIC, ACC_FINAL, ACC_SUPER
  this_class: #2                          // co/myapp/sensorPreprocessor/MqttPollerKt
  super_class: #4                         // java/lang/Object
  interfaces: 0, fields: 0, methods: 2, attributes: 2
Constant pool:
   #1 = Utf8               co/myapp/sensorPreprocessor/MqttPollerKt
   #2 = Class              #1             // co/myapp/sensorPreprocessor/MqttPollerKt
   #3 = Utf8               java/lang/Object
   #4 = Class              #3             // java/lang/Object
   #5 = Utf8               main
   #6 = Utf8               ()V
   #7 = Utf8               ([Ljava/lang/String;)V
   #8 = NameAndType        #5:#6          // main:()V
   #9 = Methodref          #2.#8          // co/myapp/sensorPreprocessor/MqttPollerKt.main:()V
  #10 = Utf8               co/myapp/sensorPreprocessor/MqttPoller
  #11 = Class              #10            // co/myapp/sensorPreprocessor/MqttPoller
  #12 = Utf8               Companion
  #13 = Utf8               Lco/myapp/sensorPreprocessor/MqttPoller$Companion;
  #14 = NameAndType        #12:#13        // Companion:Lco/myapp/sensorPreprocessor/MqttPoller$Companion;
  #15 = Fieldref           #11.#14        // co/myapp/sensorPreprocessor/MqttPoller.Companion:Lco/myapp/sensorPreprocessor/MqttPoller$Companion;
  #16 = Utf8               co/myapp/sensorPreprocessor/MqttPoller$Companion
  #17 = Class              #16            // co/myapp/sensorPreprocessor/MqttPoller$Companion
  #18 = Utf8               start
  #19 = NameAndType        #18:#6         // start:()V
  #20 = Methodref          #17.#19        // co/myapp/sensorPreprocessor/MqttPoller$Companion.start:()V
  #21 = Utf8               Lkotlin/Metadata;
  #22 = Utf8               mv
  #23 = Integer            1
  #24 = Integer            15
  #25 = Utf8               bv
  #26 = Integer            0
  #27 = Integer            3
  #28 = Utf8               k
  #29 = Integer            2
  #30 = Utf8               d1
  #31 = Utf8               \u0000\b\n\u0000\n\u0002\u0010\u0002\n\u0000\u001a\u0006\u0010\u0000\u001a\u00020\u0001¨\u0006\u0002
  #32 = Utf8               d2
  #33 = Utf8
  #34 = Utf8               sensorPreprocessor
  #35 = Utf8               MqttPoller.kt
  #36 = Utf8               Code
  #37 = Utf8               LineNumberTable
  #38 = Utf8               SourceFile
  #39 = Utf8               RuntimeVisibleAnnotations
{
  public static final void main();
    descriptor: ()V
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=1, locals=0, args_size=0
         0: getstatic     #15                 // Field co/myapp/sensorPreprocessor/MqttPoller.Companion:Lco/myapp/sensorPreprocessor/MqttPoller$Companion;
         3: invokevirtual #20                 // Method co/myapp/sensorPreprocessor/MqttPoller$Companion.start:()V
         6: return
      LineNumberTable:
        line 78: 0
        line 79: 6

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: (0x1009) ACC_PUBLIC, ACC_STATIC, ACC_SYNTHETIC
    Code:
      stack=0, locals=1, args_size=1
         0: invokestatic  #9                  // Method main:()V
         3: return
}
SourceFile: "MqttPoller.kt"
RuntimeVisibleAnnotations:
  0: #21(#22=[I#23,I#23,I#24],#25=[I#23,I#26,I#27],#28=I#29,#30=[s#31],#32=[s#5,s#33,s#34])
    kotlin.Metadata(
      mv=[1,1,15]
      bv=[1,0,3]
      k=2
      d1=["\u0000\b\n\u0000\n\u0002\u0010\u0002\n\u0000\u001a\u0006\u0010\u0000\u001a\u00020\u0001¨\u0006\u0002"]
      d2=["main","","sensorPreprocessor"]
    )

Answer 1

I've found the issue, in the jar task I had to add

exclude 'META-INF/*.RSA', 'META-INF/*.SF','META-INF/*.DSA'

so it becomes:

jar {
    manifest {
        attributes 'Main-Class': 'co.myapp.sensorPreprocessor.MqttPollerKt'
    }

    exclude 'META-INF/*.RSA', 'META-INF/*.SF','META-INF/*.DSA'

    from {
        (configurations.compile).collect {
            it.isDirectory() ? it : zipTree(it)
        }
    }
}