Creating a Java/Scala Maven project

In this post, I will explain how I set up my first program, allowing me to create and run an extremely simple Scala program in my favorite IDE using Maven.

Structure

I started out with creating the following directory structure:

scalasim
+-- src
|   +-- main
|   |   +-- java
|   |   +-- resources
|   |   \-- scala
|   |       \-- Simulation.scala
|   \-- test
|       +-- java
|       +-- resources
|       \-- scala
\-- pom.xml

Nothing exciting here – just an ordinary Maven project structure with two extra scala directories.

The POM

Creating the file pom.xml was not very exciting either; I basically copy-pasted it from the Scala website:

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<?xml version="1.0" encoding="UTF-8"?>  <project xmlns="http://maven.apache.org/POM/4.0.0"           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0                               http://maven.apache.org/maven-v4_0_0.xsd">   <modelVersion>4.0.0</modelVersion>   <groupId>nl.scalasim</groupId>   <artifactId>scalasim</artifactId>   <version>1.0-SNAPSHOT</version>   <packaging>jar</packaging>   <name>Scala SIM</name>   <description>     Tutorial application for creating a city simulation in the Scala     programming language.   </description>   <url>http://scala-simulation.blogspot.com</url>   <inceptionYear>2010</inceptionYear>   <dependencies>     <dependency>       <groupId>org.scala-lang</groupId>       <artifactId>scala-library</artifactId>       <version>2.8.0</version>     </dependency>   </dependencies>   <build>     <pluginManagement>       <plugins>         <plugin>           <groupId>org.scala-tools</groupId>           <artifactId>maven-scala-plugin</artifactId>           <version>2.9.1</version>         </plugin>       </plugins>     </pluginManagement>     <plugins>       <plugin>         <groupId>org.apache.maven.plugins</groupId>         <artifactId>maven-compiler-plugin</artifactId>         <configuration>           <source>1.6</source>           <target>1.6</target>           <encoding>UTF-8</encoding>         </configuration>       </plugin>       <plugin>         <groupId>org.scala-tools</groupId>         <artifactId>maven-scala-plugin</artifactId>         <executions>           <execution>             <goals>               <goal>compile</goal>               <goal>testCompile</goal>             </goals>           </execution>         </executions>         <configuration>           <launchers>             <launcher>               <id>main</id>               <mainClass>nl.scalasim.Simulation</mainClass>             </launcher>           </launchers>         </configuration>       </plugin>     </plugins>   </build>   <repositories>     <repository>       <id>scala-tools.org</id>       <name>Scala-tools Maven2 Repository</name>       <url>http://scala-tools.org/repo-releases</url>     </repository>   </repositories>   <pluginRepositories>     <pluginRepository>       <id>scala-tools.org</id>       <name>Scala-tools Maven2 Repository</name>       <url>http://scala-tools.org/repo-releases</url>     </pluginRepository>   </pluginRepositories> </project>

The only interesting part can be found in lines 62–67 where I added a launcher configuration which enables me to run my scala program from the command line using mvn scala:run.

Using my favorite IDE I installed the Scala plugin, imported the POM, and was ready to go.

My first program

Now, everything was ready to run, and I created the following program in src/main/scala/Simulation.scala:

object Simulation extends Application {
  println("My first Scala simulation")
}

Running the code (using mvn scala:run) resulted in the usual Maven output, interspersed with the text:

[INFO] My first Scala simulation

I did my hurray-it-works-dance, wrote this blog entry, and went on to do the next entry where actually exciting stuff will happen.

Lessons learned

Even in this short exercise, I learned a few things about Scala:

• Setting up a Scala project is just as easy as setting up an arbitrary Java project;
• Creating a small Scala program is easier than creating a similar program in Java;
• Scala's support for object definitions instead of convoluted singletons is nice.

Get the code

The full code for this post can be found at code.google.com.