Enable scala in your appengine/sculptor project

I've recently started to interest myself in the Scala language. It is a language that runs on the jvm. It's very rich in its syntax and it has a very pleasant mix of OO- and functional programming.

But since I always starts my explorations with the solid foundation of maven the first problem I encountered was how to integrate scala in my build process in a project that already mixes GAE and Sculptor. I.e. I start off from a project that has been created with our maven appengine archetype. So this is a log of my steps for making this happen.

1) In your pom, add a property for the version of Scala:

<scala.version>2.7.7</scala.version>

2) In your pom, add repository for scala:

<repository>
<id>scala-tools.org</id>
<name>Scala-Tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</repository>

3) In your pom , add pluginRepository:

<pluginRepository>
<id>scala-tools.org</id>
<name>Scala-Tools Maven2 Repository</name>
<url>http://scala-tools.org/repo-releases</url>
</pluginRepository>

4) In your pom, add dependency:

<dependency>
<groupId>org.scala-lang</groupId>
<artifactId>scala-library</artifactId>
<version>${scala.version}</version>
</dependency>

5) In your pom, add entry in maven-dependency-plugin in the build section:

<artifactItem>
<groupId>org.scala-lang</groupId>
<artifactId>scala-library</artifactId>
<version>${scala.version}</version>
<outputDirectory>war/WEB-INF/lib</outputDirectory>
</artifactItem>

6) In your pom, add dependency to specs-library (if you want it):

<dependency>
<groupId>org.specs</groupId>
<artifactId>specs</artifactId>
<version>1.4.3</version>
<scope>test</scope>
</dependency>

7) In your pom, add the scala-plugin to the build section:

<plugin>
<groupId>org.scala-tools</groupId>
<artifactId>maven-scala-plugin</artifactId>
<executions>
<execution>
 <id>scala-compile-first</id>
 <phase>process-resources</phase>
 <goals>
   <goal>add-source</goal>
   <goal>compile</goal>
 </goals>
</execution>
<execution>
 <id>scala-test-compile</id>
 <phase>process-test-resources</phase>
 <goals>
   <goal>testCompile</goal>
 </goals>
</execution>
</executions>
<configuration>
<scalaVersion>${scala.version}</scalaVersion>
<args>
 <arg>-target:jvm-1.5</arg>
</args>
</configuration>
</plugin>

8) In your project file structure, add a simple scala file: src/main/scala/org/foo/App.scala

package org.foo

/**
* Hello world!
*
*/
object App extends Application {
println( "Hello World!" )
}

9) In your project file structure, add a simple scala test: src/test/scala/org/foo/AppTest.scala

package org.foo

import org.junit._
import Assert._

@Test
class AppTest {

 @Test
 def testOK() = assertTrue(true)

}

10) In the root of your project file structure, run mvn install to see that everything builds ok