running a maven scala project

Question

Im starting to learn scala and mongo , my IDE is intellij IDEA. I created a scala project using

mvn:archetype-generate

and typed a simple h

Answer 1

maven-exec-plugin

Try with this code:

package com.example

object Main {
    def main(args: Array[String]) {
        println(5)
        val i = 1 + 2
        println(i)
    }
}

Place it under /src/main/scala/com/example/Main.scala and run it using:

$ mvn package exec:java -Dexec.mainClass=com.example.Main

If you don't want to pass mainClass manually, you can do this in plugin configuration:

  
    org.codehaus.mojo
    exec-maven-plugin
    1.1
    
      com.example.Main
    
  

There are other possibilities, this is the easiest one. Of course in IntelliJ you should be able to run the program directly.

maven-jar-plugin

If you want to ship the application, use maven-jar-plugin to add Main-Class and Class-Path entries to the manifest:

Main-Class: com.example.Main
Class-Path: lib/scala-library-2.9.0-1.jar lib/slf4j-api-1.6.1.jar ...

The following configuration does that and also copies all the dependencies (including Scala runtime library) to target/lib.

    maven-jar-plugin
    2.3.1
    
        
            
                com.example.Main
                true
                custom
                lib/$${artifact.artifactId}-$${artifact.version}$${dashClassifier?}.$${artifact.extension}
                
            
        
    


    maven-dependency-plugin
    2.3
    
        ${project.build.directory}/lib
    
    
        
            package
            
                copy-dependencies
            
        
    

Now you can simply run your application by (note the target/lib directory is required):

$ java -jar target/your_app-VERSION.jar

You can ship your application simply by copying your JAR file along with /lib subdirectory.

Also see Exec Maven Plugin and Playing with Scala and Maven.