Kotlin for Server-Side Development: A Practical Guide

Are you looking for a modern programming language that is efficient, safe and reliable to develop server-side applications? If so, then look no further than Kotlin! This programming language has rapidly gained popularity among developers for its expressive syntax, type safety, null safety, and interoperability with the industry-standard Java Virtual Machine (JVM).

This article is a practical guide for anyone who wants to develop server-side applications in Kotlin. We will explore the key features of Kotlin that make it an ideal choice for server-side development, and provide you with a step-by-step guide on how to create a web application using Kotlin.

Why Use Kotlin for Server-Side Development?

Kotlin has a lot of features that make it a top choice for server-side development. Here are some of the key benefits that Kotlin offers:

Conciseness and Readability

Kotlin syntax is concise and expressive, making it easy to read and write. You can write less code in Kotlin to achieve the same functionality as Java, thanks to features such as data classes, object expressions, extension functions, and much more. Additionally, Kotlin offers easy-to-read code, which makes it easier to maintain, refactor and scale your applications.

Interoperability with Java

Kotlin is fully interoperable with Java, which means that you can use Java libraries and frameworks in your Kotlin code, and vice versa. This interoperability is enabled by the fact that Kotlin is designed to be compiled into Java-compatible bytecode that runs on the JVM. This allows developers to use Kotlin for development of new software on established Java codebases, making many projects simpler and easier to support or update.

Type and Null Safety

Kotlin is designed with type and null safety in mind, which makes it easier to avoid common runtime errors caused by null objects or incorrect type assignments. Moreover, Kotlin provides a concise syntax to handle null objects and helps reduce the "NullPointerException" exceptions, common in Java programming, by declaring variables with an initial value or using nullable types explicitly.

Easy Concurrency with Kotlin Coroutines

Concurrency is essential for server-side development, and Kotlin offers simple and targeted tools to handle concurrency with Kotlin Coroutines. They are lightweight, fast and efficient, which makes it easier for developers to manage and ensure thread-safety in their applications. Kotlin's Coroutines handle parallel processes by allowing to write asynchronous calls without the worry of blocking or deadlocks, making them a great tool for server-side application development.

Compatibility with Popular Frameworks and Libraries

Kotlin is compatible with many popular frameworks and libraries that are widely used on the server-side such as Spring Boot, Ktor, and SparkJava. This compatibility makes it easy for developers to integrate Kotlin into existing applications, which eases the learning curve for developers new to the language, and promotes easy integration for Kotlin libraries or features.

Finally: Performance

Kotlin is designed from the ground-up to be an efficient language with JVM optimizations for the backend; it performs better than Java in many cases. Kotlin also outperforms interpreted or dynamic programming languages in terms of speed and memory allocation. Kotlin compiles to Java byte code, which makes it possible for Kotlin to run as fast or faster than Java JIT.

Building a Kotlin Server-Side Web Application

Now that we have seen why you should consider Kotlin for server-side development, let's get into the practical process of building a simple web application using Kotlin.

Set up a Development Environment

The first step to creating a Kotlin server-side application is setting up your development environment. Here are the tools that you need:

Create the Project

Once you have installed the above-mentioned tools, the next step is creating a new project in IntelliJ IDEA.

  1. Open IntelliJ IDEA.
  2. From the home screen, click on "Create New Project" or choose "File" > "New Project".
  3. Then select "Gradle" > "Kotlin/JVM" under the "New Project" popup.
  4. Enter the project name, location and other options required.
  5. Click on "Finish".

Now, you have created a new Kotlin server-side application project that allows utilizing features of both Kotlin and Java to build a robust and efficient app.

Setting up the Dependencies

Your Kotlin server-side application will require some dependencies, such as a web framework, database driver, and other necessary libraries. Gradle makes it easy to configure and manage such dependencies.

  1. Open the build.gradle directory and add dependencies to it for the framework you choose like, Spring Boot or Ktor.
  2. click on the "File" > "Sync Project with Gradle Files" option to load the dependencies and download them. 3, Restart your IDE after the dependencies update.

After the above steps are completed, your Kotlin server-side application project should have all the dependencies required to build an application.

Writing the Server-Side Code

Now that our application is set up, let's write server-side code. For the purpose of this article, we are using the Ktor framework as it comes bundled with its own lightweight HTTP server.

  1. In the project directory, add a new Kotlin file named Server.kt in the src directory.
  2. Add the necessary class and function and import the Ktor library.
    import io.ktor.application.*
    import io.ktor.response.*
    import io.ktor.routing.*
    import io.ktor.server.engine.*
    import io.ktor.server.netty.*
    fun main() {
        embeddedServer(Netty, port = 9000) {
            routing {
                get("/") {
                    call.respondText("Hello, Kotlin Server-side!")
        }.start(wait = true)

    In the above code snippet, we have added the basic HTTP server functionality using the Ktor library. The main() function is used to configure the server instance to run on port 9000. In this file, a routing block is used to map the / URL to a server response message for the root of the application.

  3. Run the application using the IntelliJ IDEA IDE's "Run" button or simply run it from the command line.

Now, your Kotlin web application server is running and configured to run at port 9000. You can test it by going to the address http://localhost:9000/ in your web browser, and it should display the message, "Hello, Kotlin Server-side!”.


In conclusion, Kotlin is a powerful and feature-rich programming language that is becoming increasingly popular for server-side development. Kotlin's strengths lie in its interoperability with Java, efficient null safety handling, easy readability, and support for popular frameworks and libraries. Building a web application using Kotlin is simple, and we have covered a practical step-by-step guide on how to create your server-side application using Ktor in Kotlin.

This tutorial is just the beginning; as there limitless possibilities with Kotlin server-side development. To take your project to the next level and develop a more advanced app, we would recommend looking into alternative frameworks such as Spring Boot, Javalin, or Vert.x, and investigating their respective advantages and drawbacks.

In the end, Kotlin proves to be a promising server-side language that offers significant advantages and makes writing efficient, robust, and scalable web applications a much smoother and more intuitive process.

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