Problem creating an executable jar from scala file - scala

Question

I'm tryign to export my project as a jar with IntelliJ 9.0. My project compiles and runs with no problem in Intellij, but when I write it to a .jar and open it, it will show an error.
My Main class is something like:
package Main
//Imports
object Main{
def main(args: Array[String]) {
println("Main: Hello, world!")
//do stuff
}
Now, in the artifacts window I created a .jar with the following:
Main Clas: Main.Main
Class Path: lib/javacsv lib/scala-compiler.jar lib/scala-library.jar lib/scalatest-1.0-test.jar lib/scalatest-1.0.jar lib/tools.jar lib/jtds-1.2.2.jar lib/flex-messaging-common.jar lib/flex-messaging-core.jar lib/spring.jar lib/mysql-connector-java-5.1.7-bin.jar lib/ojdbc14.jar lib/commons-logging.jar lib/postgresql-8.4-701.jdbc3.jar lib/log4j-1.2.15.jar lib/poi-3.6-20091214.jar lib/poi-ooxml-3.6-20091214.jar lib/dom4j-1.6.1.jar lib/poi-ooxml-schemas-3.6-20091214.jar lib/geronimo-stax-api_1.0_spec-1.0.jar lib/xmlbeans-2.3.0.jar lib/rt.jar lib/ifxjdbc.jar lib/db2jcc4.jar
I have double checked that all those classes are on the project and are the onnly classes on it. Notice that it inlcudes lib/scala-compiler.jar and lib/scala-library.jar.
Build the project: java -jar myScalaApp.jar and I get:
Exception in thread "main" java.lang.NoClassDefFoundError: scala/ScalaObject
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:675)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:288)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:374)
at Main.Main.main(Main.scala)
Caused by: java.lang.ClassNotFoundException: scala.ScalaObject
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:316)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:288)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:374)
... 13 more
I understand that it's not finding the scala classes but I made sure they are there. What else can be the problem and how could I fix it?

Answer 1

I'd say one of two things has gone wrong:
scala-library.jar is not in your jar; or
the class path at runtime doesn't include scala-library.jar.
I don't know how IntelliJ builds your jar: Does it unpack all your library jars and mung them together with your code into one big jar, or does it add the library jars as-is to your big jar and manipulate the classpath to get at the jars-within-jar?
The first point is easy enough to check: Either use jar -tvf yourJar.jar to list out the contents of your jar, or use an archive viewer to look into it graphically. Note that a .jar is basically a .zip, so you can rename the extension and then use a tool that can look into .zip files.
Just had an idea about the second part: Can you build a simple Java main class that prints out System.getProperty("java.class.path") ? A Java class should be able to run in that jar even if a Scala class isn't.

Answer 2

There are at least three ways to do this. (One applies to Netbeans but should work in Idea too)
Use jarjar as explained here
Use the idea on this page (not so elegant but the easiest) - essentially unpack the Scala directory from scala-library.jar and add this directory to your jar.
Use the idea on this page (for NB) - essentially add "scala-library.jar" to your project libraries.