ClassNotFoundException for mixed java and kotlin code when running from command line

Question

I have mixed Java & Kotlin code in a demo project which I want to run from command line. For only java, I am able to run the program with java -jar foo.jar but when I use any class from Kotlin code, it generates java.lang.NoClassDefFoundError: kotlin/jvm/internal/Intrinsics

I have tried different solutions and checked the jar file. It contains both the classes but I guess kotlin-runtime is missing from jar.

Here is build.gradle file

plugins {
    id 'java-library'
    id 'org.jetbrains.kotlin.jvm'
}

sourceSets {
    main.java.srcDirs += 'src/main/kotlin/'
    test.java.srcDirs += 'src/test/kotlin/'
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
    testImplementation 'junit:junit:4.12'
}

jar {
    manifest {
        attributes 'Main-Class': 'com.mallaudin.App'
    }
    from {
        configurations.compile.collect {
            it.isDirectory()? it: zipTree(it)
        }
    }
}

Content of generated jar file

.
├── com
│   └── mallaudin
│       ├── App.class
│       └── User.class
└── META-INF
    ├── basics.kotlin_module
    └── MANIFEST.MF

Content of MANIFEST.MF

Manifest-Version: 1.0
Main-Class: com.mallaudin.App

Exception I get when I run jar form command line

allaudin@geek ~/Desktop/KotlinLab (master) $ java -jar basics/build/libs/basics.jar 
Exception in thread "main" java.lang.NoClassDefFoundError: kotlin/jvm/internal/Intrinsics
    at com.mallaudin.User.<init>(User.kt)
    at com.mallaudin.App.main(App.java:5)
Caused by: java.lang.ClassNotFoundException: kotlin.jvm.internal.Intrinsics
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:190)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:499)
    ... 2 more

Answer 1

The issue is in the way you build your fat jar. While you use the more recent and recommended implementation scope for your dependencies, you are only adding to the fat jar the content of the compile configuration.

You should replace the configuration to be used in the fat jar by runtimeClasspath which is the full set of runtime components.

That is:

jar {
  manifest {
    attributes 'Main-Class': 'com.mallaudin.App'
  }
  from {
    configurations.runtimeClasspath.collect {
      it.isDirectory()? it: zipTree(it)
    }
  }
}  

Have a look at the documentation to understand the different dependency configurations for a java project.