Cloud Native Java: Micronaut Fundamentals

Micronaut is a modern JVM-based framework designed for building modular, easily testable microservices and serverless applications. It is designed to work with Java, Kotlin, and Groovy.

2.1 Dependency Injection

Micronaut uses compile-time dependency injection, which means that all dependencies are resolved at compile-time, leading to faster startup times and lower memory consumption.

2.2 Aspect-Oriented Programming (AOP)

AOP features allow you to define cross-cutting concerns such as logging and security without cluttering your business logic.

2.3 HTTP Client and Server

Micronaut provides a built-in HTTP client and server, making it easy to create RESTful APIs.

To get started with Micronaut, you need to have Java 11 or later installed. You can use the following command to create a new Micronaut application:

mn create-app example.micronaut.app

This command will generate a complete Micronaut application in the specified directory.

4.1 Application Structure

The generated application includes several important directories:

• src/main/java - Your Java source files.
• src/main/resources - Configuration files and other resources.
• src/test/java - Your test cases.

4.2 Writing a Controller

To create a simple REST endpoint, you can create a controller class in the src/main/java directory:

package example.micronaut.app;

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

@Controller("/hello")
public class HelloController {

    @Get
    public String index() {
        return "Hello, Micronaut!";
    }
}

4.3 Running the Application

You can run your application using:

./gradlew run

Visit http://localhost:8080/hello to see your endpoint in action.

• Keep your services small and focused on a single responsibility.
• Utilize Micronaut's built-in features for configuration management.
• Implement health checks and metrics for better observability.
• Use proper error handling and exception management.