Getting started on Java Operator SDK

Introduction to Kubernetes operators

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What are Kubernetes Operators?

Kubernetes operators are software extensions that manage both cluster and non-cluster resources on behalf of Kubernetes. The Java Operator SDK (JOSDK) makes it easy to implement Kubernetes operators in Java, with APIs designed to feel natural to Java developers and framework handling of common problems so you can focus on your business logic.

Why Use Java Operator SDK?

JOSDK provides several key advantages:

Java-native APIs that feel familiar to Java developers
Automatic handling of common operator challenges (caching, event handling, retries)
Production-ready features like observability, metrics, and error handling
Simplified development so you can focus on business logic instead of Kubernetes complexities

Learning Resources

Getting Started

Introduction to Kubernetes operators - Core concepts explained
Implementing Kubernetes Operators in Java - Introduction talk
Kubernetes operator pattern documentation - Official Kubernetes docs

Deep Dives

Problems JOSDK solves - Technical deep dive
Why Java operators make sense - Java in cloud-native infrastructure
Building a Kubernetes operator SDK for Java - Framework design principles

Tutorials

Writing Kubernetes operators using JOSDK - Step-by-step blog series

Bootstrapping and samples

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Creating a New Operator Project

Using the Maven Plugin

The simplest way to start a new operator project is using the provided Maven plugin, which generates a complete project skeleton:

mvn io.javaoperatorsdk:bootstrapper:[version]:create \
 -DprojectGroupId=org.acme \
 -DprojectArtifactId=getting-started

This command creates a new Maven project with:

A basic operator implementation
Maven configuration with required dependencies
Generated CustomResourceDefinition (CRD)

Building Your Project

Build the generated project with Maven:

mvn clean install

The build process automatically generates the CustomResourceDefinition YAML file that you’ll need to apply to your Kubernetes cluster.

Patterns and best practices

Mon, 01 Jan 0001 00:00:00 +0000

This document describes patterns and best practices for building and running operators, and how to implement them using the Java Operator SDK (JOSDK).

See also best practices in the Operator SDK.

Implementing a Reconciler

Always Reconcile All Resources

Reconciliation can be triggered by events from multiple sources. It might be tempting to check the events and only reconcile the related resource or subset of resources that the controller manages. However, this is considered an anti-pattern for operators.