Using Vaadin with Kotlin

You can use Vaadin with the Kotlin language as well. Kotlin offers awesome tooling which includes a plugin for Intellij IDEA, Eclipse and Netbeans. The plugin includes the possibility to convert any Java class to Kotlin, therefore the easiest way is to generate the sample Java Vaadin Maven project and then convert the MyUI class to Kotlin, by pressing Ctrl+Alt+Shift+K. The Kotlin plugin will convert the class and include Kotlin Maven plugin to your pom.xml.

The Karibu-DSL library offers a more Kotlin-like API for Vaadin. The library will allow you to create your UI in a hierarchical way. For more details please see Kotlin Type-Safe Builders. There is a Karibu Helloworld Application sample which demonstrates this technique. It is a standard Gradle project, thus you only need to git clone the project and open it in your IDE. The hierarchical code looks as follows:

kotlin

  1. @Theme("mytheme")
  2. class MyUI : UI() {
  4.     private lateinit var layout: VerticalLayout
  6.     @Override
  7.     override fun init(vaadinRequest: VaadinRequest) {
  8.         layout = verticalLayout {
  9.             val name = textField {
  10.                 caption = "Type your name here:"
  11.             }
  12.             button("Click Me", {
  13.                 println("Thanks ${name.value}, it works!")
  14.                 layout.label("Thanks ${name.value}, it works!")
  15.             })
  16.         }
  17.     }
  18. }

It is also possible to use Kotlin to access your database, allowing you to build full-blown web applications. For details please see the Vaadin-on-Kotlin library. Just follow the Getting Started tutorial there - the tutorial will guide you step-by-step.