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🚀 Setting Up a Java Micronaut API with Docker and Maven

Micronaut is a modern, JVM-based framework optimized for building microservices. Here's how to quickly set up a Micronaut project with Maven and Docker for local development and containerized deployment.

🛠 Prerequisites

Java 17+
Maven 3.8+
Docker
SDKMAN (optional, to install Micronaut CLI)

⚙️ 1. Create a Micronaut App (Maven)

You can generate the project using Micronaut CLI:

mn create-app com.example.hellomicronaut \
  --build maven \
  --lang java \
  --features http-server,graalvm,logback \
  --jdk 17

Or via Micronaut Launch

📁 2. Project Structure Overview

hellomicronaut/
├── src/
│ └── main/java/com/example/hellomicronaut/
│ └── Controller.java
├── pom.xml
├── Dockerfile
└── application.yml

🧱 3. Basic Controller Example

Create a controller:

📄 src/main/java/com/example/hellomicronaut/HelloController.java

package com.example.hellomicronaut;

import io.micronaut.http.annotation.*;

@Controller("/hello")
public class HelloController {
    @Get("/")
    public String index() {
        return "Hello Micronaut!";
    }
}

⚙️ 4. Run Locally

Use Maven to run the app locally:

./mvnw mn:run

Visit: http://localhost:8080/hello

🐳 5. Dockerize the App

📄 Dockerfile

FROM eclipse-temurin:17-jdk as builder
WORKDIR /app
COPY . .
RUN ./mvnw package -DskipTests

FROM eclipse-temurin:17-jdk
WORKDIR /app
COPY --from=builder /app/target/hellomicronaut-*.jar app.jar
EXPOSE 8080
ENTRYPOINT ["java", "-jar", "app.jar"]

🔨 6. Build and Run Docker Image

docker build -t micronaut-api .
docker run -p 8080:8080 micronaut-api

Access your API at http://localhost:8080/hello

⚙️ 7. Configuration (Optional)

📄 src/main/resources/application.yml

micronaut:
  application:
    name: hellomicronaut
  server:
    port: 8080

✅ 8. Test Endpoint with curl

curl http://localhost:8080/hello

Expected output:

Hello Micronaut!

📦 9. Tips for Production

Use micronaut-runtime and enable GraalVM native image support if needed.
Mount configuration via Docker volumes or environment variables.
Use micronaut-openapi for Swagger generation.
Use micronaut-security for JWT/OAuth support.

📚 References

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