How to compile scala into runnable jar file

Question

I didnt find a good way to compile scala in Linux so I tried following commands,

mkdir runnablescala
cd runnablescala
mkdir -p src/main/scala
mkdir -p src/main/resources
mkdir -p src/test/scala
mkdir -p src/test/resources
cd src/main/scala
mkdir -p com/johnathanmarksmith/gradle
vi com/johnathanmarksmith/gradle/HelloWorld.scala

package com.johnathanmarksmith.gradle;
 object HelloWorld {
    def main(args: Array[String]) {
      println("Hello, world!")
    }
  }

cd ../../..
vi build.gradle

apply plugin: 'scala' 

 jar { 
        baseName = 'smith' 
        version = '1.0' 
        manifest { 
                     attributes 'Main-Class': 'com.johnathanmarksmith.gradle.HelloWorld' } 
     }
gradle build

The build failed with this result

:compileJava UP-TO-DATE
:compileScala FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileScala'.
> 'compileScala.scalaClasspath' must not be empty

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

BUILD FAILED

Can anyone tell me how to compile scala? thanks! Do I need anyother plug in or something?

Do you mean using Gradle specifically? If yes, you should add the gradle tag. If no, SBT is usually easiest to get off the ground. — Rex Kerr, Oct 22 '15 at 22:08
I took the liberty to change tags, because that's a Gradle error, not a compiler error. — Alexey Romanov, Oct 23 '15 at 07:09
@RexKerr Is there any tutorial for using sbt to compile scala code? I've never use it before. Thanks! — Gavin Niu, Oct 23 '15 at 14:08
@GavinNiu - http://www.scala-sbt.org/documentation.html is one source. If you just want to compile one file, http://www.scala-sbt.org/0.13/tutorial/Hello.html is an example of that. If you want to build a jar file with everything needed on the classpath (and then some--it's not for optimizing, just convenience), search for the assembly plugin. — Rex Kerr, Oct 23 '15 at 14:13
@RexKerr I tried tong@tong-VirtualBox:/usr/local/jars/hello/hello$ addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.0") bash: syntax error near unexpected token `"com.eed3si9n"' How can I modify the command — Gavin Niu, Oct 23 '15 at 15:10
@GavinNiu - It's not a bash shell command! You have to put the command in the file `project/assembly.sbt`! — Rex Kerr, Oct 23 '15 at 23:16

score 4 · Answer 1 · edited May 23 '17 at 12:34

https://docs.gradle.org/current/userguide/scala_plugin.html:

Unless a task's scalaClasspath is configured explicitly, the Scala (base) plugin will try to infer it from the task's classpath. This is done as follows:

If a scala-library Jar is found on classpath, and the project has at least one repository declared, a corresponding scala-compiler repository dependency will be added to scalaClasspath.

Otherwise, execution of the task will fail with a message saying that scalaClasspath could not be inferred.

i.e. you need to add

dependencies {
  compile 'org.scala-lang:scala-library:2.11.7'
}

to build.gradle. If you want to build a stand-alone jar, see Building a uberjar with Gradle.

As Rex Kerr mentions, if you don't have a specific reason to use Gradle, I'd go with SBT for a Scala project.

Is there any tutorial for using sbt to compile scala code? I've never use it before. Thanks!! — Gavin Niu, Oct 23 '15 at 14:08

How to compile scala into runnable jar file

1 Answers1