vaadin-framework/documentation/getting-started/getting-started-scala.asciidoc

---
title: Using Vaadin with Scala
order: 1000
layout: page
---

[[getting-started.scala]]
= Using Vaadin with Scala

You can use Vaadin with any JVM compatible language, such as Scala or Groovy.
There are, however, some caveats related to libraries and project set-up. In the
following, we give instructions for creating a Scala UI in Eclipse, with the
Scala IDE for Eclipse and the Vaadin Plugin for Eclipse.

. Install the link:http://scala-ide.org/[Scala IDE for Eclipse], either from an
Eclipse update site or as a bundled Eclipse distribution.

. Open an existing Vaadin Java project or create a new one as outlined in
<<dummy/../../../framework/getting-started/getting-started-first-project#getting-started.first-project,"Creating
and Running a Project with Eclipse">>. You can delete the UI class created by
the wizard.

. Switch to the Scala perspective by clicking the perspective in the upper-right
corner of the Eclipse window.

. Right-click on the project folder in [guilabel]#Project Explorer# and select
"Configure > Add Scala Nature".

. The web application needs [filename]#scala-library.jar# in its class path. If
using Scala IDE, you can copy it from somewhere under your Eclipse installation
to the class path of the web application, that is, either to the
[filename]#WebContent/WEB-INF/lib# folder in the project or to the library path
of the application server. If copying outside Eclipse to a project, refresh the
project by selecting it and pressing kbd:[F5].

+
You could also get it with a Maven dependency, just make sure that the
version is same as what the Scala IDE uses.


You should now be able to create a Scala UI class, such as the following:


[source, scala]
----
@Theme("mytheme")
class MyScalaUI extends UI {
  override def init(request: VaadinRequest) = {
    val content: VerticalLayout = new VerticalLayout
    setContent(content)

    val label: Label = new Label("Hello, world!")
    content addComponent label

    // Handle user interaction
    content addComponent new Button("Click Me!",
      new ClickListener {
        override def buttonClick(event: ClickEvent) =
          Notification.show("The time is " + new Date)
      })
  }
}
----

Eclipse and Scala IDE should be able to import the Vaadin classes automatically
when you press kbd:[Ctrl+Shift+O].

You need to define the Scala UI class either in a servlet class (in Servlet 3.0
project) or in a [filename]#web.xml# deployment descriptor, just like described
in
<<dummy/../../../framework/getting-started/getting-started-first-project#getting-started.first-project.exploring,"Exploring
the Project">> for Java UIs.

ifdef::web[]
The link:https://github.com/henrikerola/scaladin[Scaladin add-on] offers a more
Scala-like API for Vaadin. A Vaadin 7 compatible version is under development.
endif::web[]

ifdef::web[]
[[getting-started.scala.lambdas]]
== Defining Listeners with Lambda Expressions

Scala does not support use of lambda expressions for calling functional
interfaces, like Java 8 does. Hence, we can't just use a lambda expression for
the [interfacename]#ClickListener# in the example above. You can, however,
define implicit conversions from lambda expressions to such interface
implementations. For example, for click listeners:


[source, scala]
----
implicit def clickListener(f: ClickEvent => Unit) =
  new ClickListener {
    override def buttonClick(event: ClickEvent) {
      f(event)
    }
  }
----

You could then use a lambda expression as follows:


[source, scala]
----
content addComponent new Button("Click Me!",
  (event: ClickEvent) =>
      Notification.show("The time is " + new Date))
----

endif::web[]