java.lang.NoClassDefFoundError: scala/collection/immutable/Seq

[danielbasso]

Hello,

I received a Gradle Scala project from a colleague that is working in production, and I'm trying to run it on my machine. When I try to run, this error appear:

Exception in thread "main" java.lang.NoClassDefFoundError: scala/Serializable
    (...)
Caused by: java.lang.ClassNotFoundException: scala.Serializable

I can't find a good answer to this error online. I also should mention that I receive this message when running from Visual Studio Code:

2021.12.03 18:11:49 INFO no build target: using presentation compiler with only scala-library: 2.13.5

Gradle settings:

    apply plugin: 'scala'
    apply plugin: 'java'
    apply plugin: 'idea'

    idea {
    	module {
    		inheritOutputDirs = true
    		downloadJavadoc = false
    		downloadSources = false
    	}
    }

    sourceCompatibility = 1.11
    targetCompatibility = 1.11
    def scalaVersion = '2.13.5'
    def scalaRelease = scalaVersion.split('\\.').take(2).join('.')

    repositories {
    	mavenCentral()
    	maven {url "https://repository.cloudera.com/artifactory/cloudera-repos/"}
    }

    //def deploy = 'desm'
    def deploy = 'prod'

    dependencies {
    	if (deploy == 'prod') {
    		compileOnly "org.scala-lang:scala-library:$scalaVersion"
    		compileOnly group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.11.2'
    		compileOnly group: 'com.fasterxml.jackson.module', name: "jackson-module-scala_$scalaRelease", version: '2.11.2'
    		compileOnly group: 'org.apache.hbase', name: 'hbase-client', version: '2.1.0-cdh6.3.3'
    		compileOnly group: 'org.apache.kafka', name: 'kafka-clients', version: '2.2.1-cdh6.3.3'
    	}else if (deploy == 'desm'){
    		compile "org.scala-lang:scala-library:$scalaVersion"
    		compile group: 'com.fasterxml.jackson.core', name: 'jackson-databind', version: '2.11.2'
    		compile group: 'com.fasterxml.jackson.module', name: "jackson-module-scala_$scalaRelease", version: '2.11.2'
    		compile group: 'org.apache.hbase', name: 'hbase-client', version: '2.1.0-cdh6.3.3'
    		compile group: 'org.apache.kafka', name: 'kafka-clients', version: '2.2.1-cdh6.3.3'
    	}
    	compile group: 'ml.dmlc', name: 'xgboost4j', version: '0.72', {
    		exclude group: 'com.typesafe.akka', module: 'akka-actor_2.11'
    		exclude group: 'com.typesafe.akka', module: 'akka-testkit_2.11'
    		exclude group: 'junit', module: 'junit'
    		exclude group: 'org.scala-lang', module: 'scala-compiler'
    		exclude group: 'org.scala-lang', module: 'scala-reflect'
    		exclude group: 'org.scala-lang', module: 'scala-library'
    		exclude group: 'org.scalatest',  module: 'scalatest_2.11'
    	}
    }

JVM: 11.0.13
XGBoost: 0.72 (It's an old version, I know)
Scala: 2.13.5

Some answers online point out to the absence of an library called scala-library. In my project, this library does appear:

And in bloop:

What could be wrong?

[kpodsiad]

Looks like scala/bug#11832

[danielbasso]

I've just realized something. My project has .bloop folder and inside it a .json file with the name of my project. This json has two properties:

{
    "classpath": [(list of jars - 1)],
    (...)
    "platform": {
            "name": "jvm",
            "config": {
                "home": "/usr/lib/jvm/jdk-11.0.13+8",
                "options": [
                    
                ]
            },
            "mainClass": [
                
            ],
            "classpath": [(another list of jars - 2)]
} 

It seems that only the jars in the list nr. 2 count as I'm debugging, or simply trying to run my code. But the second list has waaay less jars than the list nr.1 . If I manually add a jar from the first list to the second, the error related to that jar disappears. Could you explain in layman's terms why is this? There is a simple option to copy all jars from the project classpath to the jvm classpath?

[kpodsiad]

That's a boomer, I think it should just work, but I'll take a closer look at this tomorrow.

[danielbasso]

I've downgraded the scala version to 2.12.15 than copied the project classpath to the jvm classpath and now it's working. But I'm still little puzzled why they aren't the same to begin with.

[kpodsiad]

I'm not a Gradle expert but compileOnly caught my attention. According to this article dependencies added as compile only ones shouldn't appear on the runtime classpath. It matches what you described, that the second classpath (runtime) is much smaller than the first one (compile).

Here's pic from linked article

[danielbasso]

That's it. Great advice. The code has:

//def deploy = 'desm'
def deploy = 'prod'

So it was using production settings, which only create the "Compile classpath". The word "compile" is the old word for "implementation", so that makes sense. Thanks a lot!

Now, about the version 2.13.5 I will still have to check it out.