Executable Scala Jar from Eclipse using Java main class

Question

I am trying to create an executable Jar from my Scala project. Therefore, I followed a tutorial. It suggested creating a Java main class within eclipse, which calls the Scala entry point. This works fine when executing within eclipse. After adding this class I was able to export an executable jar. However, it wont work with

java -jar myjar.jar

I made sure to activate "Package required library into jar" when exporting. My Java main class looks like this (where Driver is also located in the package core)

package core;

public class Main {
     public static void main(String[] args) {
        Driver.main(args);
    }
}

And when executing the exported char the follwing error is thrown, which I can debug:

Exception in thread "main" java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
Caused by: java.lang.NoClassDefFoundError: scala/collection/Seq
    at core.Driver$.main(Driver.scala:14)
    at core.Driver.main(Driver.scala)
    at core.Main.main(Main.java:5)
    ... 5 more
Caused by: java.lang.ClassNotFoundException: scala.collection.Seq
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)

Scott Greene · Accepted Answer · 2014-08-27 16:53:42Z

1

You could use the One-jar application to guarantee all the necessary jars are in the jarfile, I suspect the scala-lang jars are not in it or in the classpath of the command line.

Maven: https://code.google.com/p/onejar-maven-plugin/ SBT: https://github.com/sbt/sbt-onejar

If you aren't using either maven or SBT I would suggest switching to them as well as they are the main supported build systems in Scala

answered Aug 27, 2014 at 16:53

Scott Greene

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1 Comment

smoes Over a year ago

I used sbt, not with onejar, but assembly. It worked great and was easy to setup. However, I had some little problems with Maven. To be honest I did not try that hard, since I had sbt already running ;) I accept your answer, however it would be even finer, if others would directly answer my question!

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