kotlin+Sparkでハンズオンを行うまでの知見

 $ kotlinc src/hello.kt -include-runtime -d jar/hello.jar
 $ java -jar jar/hello.jar 

FROM zenika/alpine-kotlin
RUN apk add gradle

version: '3'
services:
  app:
    build: .
    container_name: kotlin
    working_dir: /app
    volumes:
      - ./:/app
    ports:
      - "4567:4567"

$ gradle init

plugins {
  id "org.jetbrains.kotlin.jvm" version "1.3.72"
}

apply plugin: 'kotlin'
apply plugin: 'application'
mainClassName = 'demo.HelloKt'

defaultTasks 'run'

repositories {
  mavenCentral()
}

dependencies {
  compile "org.jetbrains.kotlin:kotlin-gradle-plugin:1.3.72"
  compile "com.sparkjava:spark-core:2.6.0"
}

└── src
    ├── main
    │   ├── kotlin

.
└── src
    ├── main
    │   ├── kotlin
    │   │   ├── demo
    │   │   │    ├── Hello.kt

package demo
import spark.Spark.get

fun main(args: Array<String>) {
		get("/hello") { req, res -> "Hello World" }
}

$ gradle

FROM gradle:5.4-jdk-alpine

ENV APP_ROOT /usr/src/app

WORKDIR $APP_ROOT

USER root

RUN apk add --no-cache curl \
	zip \
	libc6-compat \
	bash

RUN ln -s /lib/libc.musl-x86_64.so.1 /lib/ld-linux-x86-64.so.2

RUN curl -s https://get.sdkman.io | bash

RUN bash -c " \
	source "$HOME/.sdkman/bin/sdkman-init.sh" && \
	sdk install kotlin 1.3.72 \
	"