DevOps for Java Developers: How to Get Started with Docker and Kubernetes

Why DevOps Is Essential for Java Developers

In the past, a developer’s responsibilities were limited to writing code and unit tests. Once compiled, the code was handed off to deployment teams or client-side administrators. Today, this model has evolved. With the rise of cloud computing, containerization, and the DevOps culture, the boundaries between development and operations have blurred.

Modern development practices increasingly require developers to understand how to package applications into containers and manage them effectively. This shift is not due to convenience but necessity. In the era of microservices—where local environments, integration testing, and CI/CD pipelines are common—basic knowledge of containerization is indispensable.

This article explores the first steps with Docker and Kubernetes from a Java developer’s perspective.

Docker, Virtual Machines, and Kubernetes – Core Concepts

Server – a physical machine providing resources such as applications. Traditionally, Java applications were deployed directly on servers, often resulting in dependency conflicts and maintenance challenges.

Virtual Machine (VM) – an isolated environment running on a server. Virtualization enables multiple operating systems on a single machine. Each VM has its own OS and libraries, preventing conflicts. However, VMs consume more resources and have slower startup times.

Docker / Container – lightweight, fast runtime environments that share the host OS, making them more efficient than VMs. A container includes only what is necessary—such as JDK, libraries, and the application—resulting in minimal resource usage and near-instant startup. This allows significantly more containers than VMs on the same hardware, though managing large numbers of containers can be complex.

Kubernetes – a container orchestration platform that automates deployment, monitoring, scaling, and recovery, reducing manual intervention and improving reliability.

How Docker Simplifies Java Application Deployment

Consider a Spring Boot application. Traditionally, it runs locally via Maven (mvn spring-boot:run), while in production, administrators configure servers and deploy the application. With Docker, you create a portable image that runs consistently across development, testing, and production environments.

Key benefits of Docker in DevOps:

• Scalability and automation – lightweight containers are easy to replicate, enabling efficient orchestration.
• Environment consistency – identical behavior across local, test, and production environments.
• Faster deployment – no need to copy JAR/WAR files and configure servers; simply start a container.
• Isolation and security – containers run in isolated environments, minimizing conflicts.

Building a Docker Image for a Spring Boot Application

A typical workflow includes:

1. Build the application – use Maven to generate a JAR or WAR in the target/ directory.
2. Create a Dockerfile – define the base image (e.g., Java 17), set the working directory, copy the JAR, and specify the startup command.
3. Build the image – run docker build to create the Docker image.
4. Run the container – execute docker run -p 8080:8080 to start the application and map ports.

Your application now runs inside a containerized environment.

Why Kubernetes Is Critical in Modern DevOps

Docker is ideal for single-container deployments. However, scaling applications or managing thousands of containers requires orchestration. Kubernetes (K8s) addresses this challenge by automating scaling, configuration management, secret handling, and failover recovery. Think of Docker as a single package and Kubernetes as the logistics system managing thousands of packages.

Deploying a Java Application on Kubernetes – Step by Step

1. Build the application – create a Spring Boot app using Maven.
2. Create a Docker image – prepare the runtime environment.
3. Run the container locally.
4. Orchestrate with Kubernetes – deploy multiple instances, scale automatically based on traffic, and ensure high availability.

Kubernetes Essentials for Beginners

• Pod – the smallest deployable unit, which may contain multiple containers.
• Deployment – defines how the application should run and update.
• Service – exposes the application externally and balances traffic across Pods.
• ConfigMap and Secret – store configuration and sensitive data securely.
• Ingress – manages HTTP access to applications.

Getting Started Locally with Minikube

Running Kubernetes in production requires infrastructure, which can be costly. Minikube provides a lightweight way to run a local Kubernetes cluster for development and testing.

Adopting the DevOps Mindset

Applications are more than just code—they are deployable packages. Testing within containers ensures consistent behavior across environments and simplifies automation. Instead of manual commands, developers should leverage scripts and CI/CD pipelines to streamline deployments.

Summary: What Java Developers Need to Know

Docker and Kubernetes have transformed software delivery. Today, developers are not only writing code but also managing the systems that run it. These technologies enable efficient packaging, portability, and scalability. To remain competitive, Java developers must master these tools alongside their programming skills.

---

Author: Sebastian Pieróg, Senior Fullstack Java Developer, ALTEN Polska

Related articles