CODEWITHSUNDEEP
scalajarjvmuberjar
schwadan
schwadan

Reputation: 158

Running multiple Scala apps from one jar on JVM

I have a Scala application that successfully runs on the JVM using an uber jar via the command: java -jar myapp.jar. I need to create a separate, but related Scala job that utilizes many of the same objects/functions/dependencies as the first, making it a great candidate to keep in the same code repository & uber jar. Please note that these Scala jobs do not utilize Spark, so spark2-submit is out of the equation.

Question: How can I run 2 separate Scala jobs from the same uber jar on the JVM? (I am using Scala 2.11.8 and SBT for jar assembly)

Additional Context:

I've already looked into related StackOverflow discussions, namely this post about specifying Java classes using java -cp myapp.jar MyClass and this post, which only presented the solution of running the Scala equivalent using scala -classpath myapp.jar MyClass.

While the scala -classpath solution may have worked for the OP of the second linked discussion, I'll be deploying my code to an environment that doesn't have executables for scala or sbt, only java.

Let's say these are the 2 Scala jobs I want to run:

// MyClass.scala
package mypackage

object MyClass {
  def main(args: Array[String]): Unit = {
    println("Hello, World!")
  }
}

// MyClass2.scala
package mypackage

object MyClass2 {
  def main(args: Array[String]): Unit = {
    println("Hello, World! This is the second job!")
  }
}

Is there a way to run Scala code using java -cp myapp.jar MyClass? I've tried this and receive the following error:

Error: Could not find or load main class MyClass

The main alternative I can think of would be to create a Scala object that serves as a main entry point and takes a parameter to determine which job gets run. I'd like to avoid that solution if possible, but it would allow me to continue using java -jar myapp.jar, which has been working fine.

Upvotes: 2

Views: 502

Answers (1)

Tim
Tim

Reputation: 27356

You need to use a fully qualified name for the App instance:

java -cp myapp.jar mypackage.MyClass

Upvotes: 4

Related Questions