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Scala and Vaadin HOWTO

Introduction #

Since Vaadin is a server-side library it works very well with all JVM languages, including Scala. This article provides instructions on how to get started with Vaadin using Scala. First, we'll go through setting up a new project. After that we'll introduce the Scaladin add-on and see how it enhances Vaadin components by adding features that leverage the power of Scala.

Creating a new Eclipse Vaadin project with Scala #

Installing the required software components #

  • Download and install Eclipse Helios or Indigo by unpacking it to a location of your choice. Please note that only Eclipse Helios is officially supported by Scala IDE but also Indigo can be used.
  • Start Eclipse, and install the Vaadin Eclipse Plug-in and Scala IDE Eclipse Plug-in using the plug-in installation feature of Eclipse (available under Help -> Install New Software...).

You also need a servlet container to run your application. In this example we use Tomcat, but any standard container (Jetty, JBoss, Glassfish, Oracle WebLogic, IBM WebSphere etc.) should be fine.

  • Download and install Tomcat by unpacking it to a location of your choice.
  • Add the server to Eclipse
  • Open the Servers view
  • Right click in the Servers view and choose New -> Server
  • Choose the type of your server, in this case Apache -> Tomcat
  • Choose the server runtime environment in the dialog by selecting the folder you unpacked Tomcat to.

Creating a new project #

  • Create a new Vaadin project in Eclipse:
  • Choose File -> New...
  • Choose Other...
  • Choose Vaadin -> Vaadin Project from the list. You can use the filter to narrow down the list.
  • Choose a name for your project, eg. "ScalaTest"
The New Vaadin Project Wizard allows you to configure different aspects your project, but the defaults are fine.

At this point you have a ready-to-go Vaadin Java project. To start doing Scala we need to do a few more things:

  • Add the Scala nature to your project: right click your project root, and choose Configure -> Add Scala Nature from the menu.
  • Navigate to the src folder, and delete the generated Java file under the default package (eg. com.example.scalatest)

Next up, some Scala!

  • Add a new Scala class in your project: right click the default package, and choose New -> Scala Class
  • Choose a name for the class, eg. "ScalaApp"
  • Our new class should extend the com.vaadin.Application, so in the wizard, click the Browse... button next to the "Superclass" field, and choose that from the list.
  • Click "Finish" to let Eclipse generate the class.

Now we need to write some code in the method of our new Vaadin application.

  • Open the ScalaApp.scala
  • Add the following lines in the init() method:
setMainWindow(new Window("Scala Rocks!"))
getMainWindow.addComponent(new Label("Hello World!"))

You can let Eclipse add the imports as you go, or just import the Vaadin components (import com.vaadin.ui._) yourself. The resulting file should look like this:

import com.vaadin.Application
import com.vaadin.ui._

class ScalaApp extends Application {
	def init(): Unit = {
		setMainWindow(new Window("Scala Rocks!"))
		getMainWindow.addComponent(new Label("Hello World!"))
	}
}

Next we make sure the servlet container knows which class it should load.

  • Open WebContent/WEB-INF/web.xml
  • Under the <web-app><servlet> branch change the param-value of the application init-param to contain to your application class, including the package name. Eg. "com.example.scalatest.ScalaApp"

Additional configuration #

We're almost done. The last thing we need to do is make sure that the scala-library.jar is available at runtime. We do this by adding the JAR into the classpath of our servlet container.

First, we need the JAR file itself. You already have this in the Scala IDE installation folder under Eclipse, or you can download the Scala distribution from http://www.scala-lang.org/downloads.

We have a few options how to make sure the JAR is available at runtime.

  • Put the file in the WEB-INF/lib folder under your project.
  • Put the file directly in the lib folder of your servlet container.
  • Add the Scala library to the deployment assembly: project properties -> Deployment assembly -> Add... -> Java build path entries

After you have done this we can fire up our application!

Running the application #

Running the application is simple

  • Right click your project, and choose Run As -> Run On Server
  • Choose the previously created Tomcat instance as the target. You might also want to check the "Always use this server when running this project" checkbox.

Eclipse should then start the server and open the UI in a internal browser window.

Creating a new project using a Giter8 template #

Giter8 is a command-line tool that generates project skeletons from templates that are published on GitHub. The Vaadin-Scala template creates the basic structure for a SBT-project that has Vaadin, Scala and Scaladin included.

First, install Giter8 following the instructions on their readme. Then just

g8 ripla/vaadin-scala
And answer the questions, or press enter for defaults. After that launch the server (jetty):
cd <project dir>
sbt
container:start
You can then browse to http://localhost:8080 for the app. The created project is a standard SBT-project that uses the normal maven style layout, so you'll find the application source from src/main/scala.

To create Eclipse project files, type eclipse in the sbt prompt. After this, the project can be imported as an Eclipse project.

Scaladin #

Scaladin is a library that extends Vaadin and adds Scala-like features to Vaadin classes. It's just a single add-on (one JAR) and is highly recommended for any Scala Vaadin development. See the GitHub wiki and the Directory page for more information.
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