Dockerizing Scala Applications

Introduction

Docker is a powerful tool that allows developers to package applications and their dependencies into a standardized unit called a container. This tutorial will guide you through the process of Dockerizing a Scala application, enabling you to run your application consistently across different environments.

Prerequisites

Before you begin, ensure you have the following installed:

• Java Development Kit (JDK)
• SBT (Scala Build Tool)
• Docker

Setting Up a Sample Scala Application

Create a simple Scala application using SBT. First, create a new directory for your project:

Follow the prompts to set up your project. This will create a basic Scala application structure.

Writing a Simple Application

Open the generated project and modify the src/main/scala/Main.scala file. Replace its contents with the following simple program:

object Main {
    def main(args: Array[String]): Unit = {
        println("Hello, Dockerized Scala!")
    }
}
                

This program simply prints a message to the console.

Creating a Dockerfile

The next step is to create a Dockerfile in the root of your project directory. This file contains instructions on how to build the Docker image for your Scala application. Create a file named Dockerfile with the following content:

# Use the official Scala image as the base image
FROM frolvlad/alpine-scala:latest

# Set the working directory
WORKDIR /app

# Copy the build files
COPY . .

# Build the Scala application
RUN sbt compile

# Command to run the application
CMD ["sbt", "run"]
                

This Dockerfile uses a lightweight Scala image, sets the working directory, copies the application files, compiles the Scala application, and finally specifies the command to run the application.

Building the Docker Image

Open your terminal, navigate to your project directory, and build the Docker image using the following command:

This command builds the Docker image and tags it as scala-docker-example.

Running the Docker Container

Once the image is built, you can run it in a Docker container:

The --rm flag automatically removes the container when it exits. You should see the output:

Hello, Dockerized Scala!

Conclusion

You have successfully Dockerized a Scala application! This process allows you to run your application in any environment that supports Docker, ensuring consistency and ease of deployment. You can further explore Docker's features, such as networking and volume management, to enhance your applications.