This is a very short tutorial

If you need to learn how to setup Kotlin with Maven, please follow the beginning of our Kotlin CRUD REST API tutorial

Dependencies

<dependency>
    <groupId>io.javalin</groupId>
    <artifactId>javalin-bundle</artifactId>
    <version>6.7.0</version>
</dependency>

Our main class

import io.javalin.http.staticfiles.Location
import io.javalin.http.bodyAsClass

data class Todo(val id: Long, val title: String, val completed: Boolean)

fun main() {

    var todos = arrayOf(Todo(123123123, "My very first todo", false))

    val app = Javalin.create {
        it.staticFiles.add("/public", Location.CLASSPATH)
        it.router.mount {
            it.get("/todos") { ctx ->
                ctx.json(todos)
            }
            it.put("/todos") { ctx ->
                todos = ctx.bodyAsClass<Array<Todo>>()
                ctx.status(204)
            }
        }
    }.start(7070)

}

We’re use Javalin to serve our static files, as well as handle two endpoints: get and put.

Most of the work here is being done by ctx.json and ctx.bodyAsClass, which map a Todo data-class:

data class Todo(val id: Long = -1, val title: String = "", val completed: Boolean = false)

That’s it. The rest of the logic is in index.html (vue template) and todomvc.js (vue logic).
This is not a JavaScript tutorial, so please have a look at those files for yourself.