A sample Kotlin app using Spark framework in AWS Lambda.

Handler.kt

package com.example.lambda

import com.amazonaws.serverless.exceptions.ContainerInitializationException
import com.amazonaws.serverless.proxy.model.AwsProxyRequest
import com.amazonaws.serverless.proxy.model.AwsProxyResponse
import com.amazonaws.serverless.proxy.spark.SparkLambdaContainerHandler
import com.amazonaws.services.lambda.runtime.Context
import com.amazonaws.services.lambda.runtime.RequestHandler
import spark.Request
import spark.Response
import spark.Spark.*

class Handler @Throws(ContainerInitializationException::class)
constructor() : RequestHandler<AwsProxyRequest, AwsProxyResponse> {
    private val handler = SparkLambdaContainerHandler.getAwsProxyHandler()
    private var initialized = false

    override fun handleRequest(request: AwsProxyRequest, context: Context?): AwsProxyResponse {
        if(!initialized){
            initRoutes()
            initialized = true
        }
        return handler.proxy(request, context)
    }

    companion object {
        @kotlin.jvm.JvmStatic
        fun main(args: Array<String>){
            initRoutes()
        }

        private fun initRoutes(){
            initExceptionHandler { e ->
                println("Spark initialization failed")
                System.exit(100)
            }

            path("/greetings"){
                get(""){_, _ -> "Hello World"}
                get("/:name"){req, res -> greetName(
                        req,
                        res
                )}
            }
        }

        private fun greetName(req: Request, res: Response): String {
            val name = req.params("name") ?: ""
            return "Hello $name"
        }
    }
}