Creating Your First Micronaut Application

Introduction

Micronaut is a modern, cloud-native Java framework built for microservices and serverless applications. Unlike traditional Java frameworks, Micronaut focuses on:

• Fast startup times
• Low memory consumption
• Compile-time dependency injection

In this tutorial, you will create your first Micronaut application from scratch using the package name com.kscodes.micronaut. Don’t worry — no prior experience with Micronaut is required!

Why Micronaut?

Before we jump into coding, let’s understand why many developers choose Micronaut:

• Minimal runtime overhead.
• No reflection — faster and safer.
• Built-in support for reactive programming.
• Great for microservices architecture.
• Excellent integration with cloud services.

Prerequisites

Before we begin, make sure you have the following:

For a maven based project you can go through the Installing Micronaut CLI and Setting Up Your First Project

Step 1 — Install Micronaut CLI

Install via SDKMAN

If you use SDKMAN, installation is super easy:

sdk install micronaut

Verify installation

mn --version

Step 2 — Generate Micronaut Application

Now let’s scaffold your first Micronaut application.

mn create-app com.kscodes.micronaut.demo –build=gradle –lang=java

• com.kscodes.micronaut.demo — package name
• --build=gradle — Gradle as the build system
• --lang=java — language is Java

✅ Tip: You can replace demo with your project name.

Step 3 — Understanding Project Structure

Micronaut will generate a ready-to-use project:

demo/
├── build.gradle
├── src/
│   ├── main/
│   │   ├── java/com/kscodes/micronaut/demo/
│   │   │   └── Application.java
│   └── test/
├── gradlew
└── README.md

Step 4 — Writing Your First REST Endpoint

Let’s build a simple greeting API.

Create Controller

Create a new file:
src/main/java/com/kscodes/micronaut/demo/GreetingController.java

package com.kscodes.micronaut.demo;

import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;

@Controller("/greet")
public class GreetingController {

    @Get("/{name}")
    public String greet(String name) {
        return "Hello, " + name + "!";
    }
}

Explanation

• @Controller("/greet") — base URL path.
• @Get("/{name}") — accepts name as a path parameter.
• Returns a greeting message.

Step 5 — Run the Application

Start the application:

gradlew run

Step 6 — Test the API

Open your browser or API tool (Postman, Curl, etc.)

http://localhost:8080/greet/John

Response

Hello, John!

🎉 Congratulations! You’ve successfully created your first Micronaut REST API.

Step 7 — Add Health Check

Micronaut provides built-in health endpoints.

Enable Management Endpoints

Add to src/main/resources/application.yml:

micronaut:
  application:
    name: demo
  server:
    port: 8080
endpoints:
  health:
    enabled: true
    sensitive: false

Now visit:

http://localhost:8080/health

You’ll see health information for your app.

Step 8 — Build a Fat JAR

To package the application for deployment:

gradlew assemble

The fat JAR will be in:

build/libs/

Step 9 — Where to Go Next

Now that you have your basic Micronaut app running, you can explore:

• Micronaut Data — for database access.
• Micronaut Security — for authentication/authorization.
• Micronaut Messaging — for Kafka/RabbitMQ integration.
• Deploy to Cloud — AWS Lambda, Google Cloud Functions, Azure Functions.

Conclusion

Micronaut simplifies microservices development while keeping things blazing fast and memory-efficient. You’ve successfully:

• Installed Micronaut CLI
• Created your first Micronaut app
• Built and tested a REST API

From here, the Micronaut ecosystem offers a huge set of features to explore.