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Deploying a Kotlin Application

Deploying a Kotlin application might seem daunting at first, especially if you're a beginner, but don't worry! This tutorial will guide you through the process from start to finish. We'll be covering everything from creating a simple Kotlin application to deploying it on a server. Let's get started!

Step 1: Creating a Simple Kotlin Application​

Before we can deploy an application, we need to have an application to deploy! So, let's start by creating a simple HelloWorld application.

First, install the Kotlin compiler by following the instructions on the official Kotlin website. Once you've done that, create a new file called HelloWorld.kt and add the following code:

fun main(args: Array<String>) {
    println("Hello, World!")
}

You can run this application locally by using the Kotlin compiler:

kotlinc HelloWorld.kt -include-runtime -d HelloWorld.jar
java -jar HelloWorld.jar

Step 2: Packaging the Application​

Packaging is the process of combining compiled code into a format that can be easily distributed and used. In Kotlin, we typically package applications into a JAR (Java Archive) file. When we ran our HelloWorld application in the previous step, we already created a JAR file. Let's take a closer look at the commands we used:

kotlinc HelloWorld.kt -include-runtime -d HelloWorld.jar

This command tells the Kotlin compiler to compile the HelloWorld.kt file, include the Kotlin runtime in the JAR file (which is necessary to run the application), and produce a JAR file named HelloWorld.jar.

Step 3: Deploying the Application​

Now comes the fun part - deploying our application! In this tutorial, let's deploy our application on a simple server. We'll be using Docker for this purpose.

First, you need to install Docker on your machine. Refer to the official Docker installation guide for instructions.

Next, create a Dockerfile in the same directory as your HelloWorld.jar file. The Dockerfile should look like this:

FROM openjdk:8-jre-alpine
COPY ./HelloWorld.jar /app/
CMD ["java", "-jar", "/app/HelloWorld.jar"]

This Dockerfile tells Docker to:

  1. Start with a base image that includes the Java 8 runtime (openjdk:8-jre-alpine).
  2. Copy the HelloWorld.jar file into the /app/ directory inside the Docker image.
  3. When a container is started from this image, run the command java -jar /app/HelloWorld.jar to start our application.

Now we can build a Docker image and start a container:

docker build -t helloworld:latest .
docker run -p 8080:8080 helloworld:latest

Congratulations! You've just deployed a Kotlin application.

Deploying a Kotlin application involves several steps, including writing the application, packaging it into a JAR file, and deploying it using Docker. While there are many ways to deploy a Kotlin application, this tutorial provides a simple and straightforward method suitable for beginners. As you gain more experience with Kotlin and deployment strategies, you can explore more complex deployment options.