Building an Application with Micronaut

Hello everyone, today we will learn how to create a Micronaut based project via Micronaut Launch.

Micronaut is a modern, JVM-predicated, full-stack Java framework designed for building modular, facilely testable JVM applications with support for Java, Kotlin and the Groovy language.

Micronaut  provides:

  • Dependency Injection and Inversion of Control (IoC)
  • Aspect-Oriented Programming (AOP)
  • Sensible Defaults and Auto-ConfigurationMessage-Driven Applications
  • HTTP Routing
  • Client-Side Load Balancing
  • Command-Line Applications
  • HTTP ServersDistributed Configuration
  • Service Discovery
  • Fast startup time
  • Reduced memory footprint
  • Minimal use of reflection
  • Minimal use of proxies
  • No runtime bytecode generation
  • Easy Unit Testing

What We Will build today?

We will build a simple web hello world application with Micronaut.

Technologies used:

  • Java 11
  • Micronaut 3.1.1
  • Maven 3.6.3
  • IntelliJ IDEA

Starting with Micronaut Launch

  • Navigate to https://micronaut.io/launch/ This service pulls in all the dependencies you need for an application and does most of the setup for you.

  • Choose Application Type - Micronaut Application
  • Choose Java Version - Java 11
  • Enter the Application Name - helloworld
  • Enter the Base package - org.knf.dev.demo
  • Choose Micronaut Version - 3.1.1
  • Choose Language - Java
  • Choose either Gradle or Maven or Gradle or Kotlin - Maven
  • Choose Test Framework - JUnit
  • Click Generate
  • Download the resulting ZIP file, which is an archive of a web application that is configured with your choices.
  • Open the Project in your favourite IDE, I am using IntelliJ IDEA

Project Directory:


Dependency management:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.knf.dev.demo</groupId>
<artifactId>micronaut-helloworld</artifactId>
<version>0.1</version>
<packaging>${packaging}</packaging>

<parent>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-parent</artifactId>
<version>3.1.1</version>
</parent>

<properties>
<packaging>jar</packaging>
<jdk.version>11</jdk.version>
<release.version>11</release.version>
<micronaut.version>3.1.1</micronaut.version>
<exec.mainClass>org.knf.dev.demo.Application</exec.mainClass>
<micronaut.runtime>netty</micronaut.runtime>
</properties>

<repositories>
<repository>
<id>central</id>
<url>https://repo.maven.apache.org/maven2</url>
</repository>
</repositories>

<dependencies>
<dependency>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-inject</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-validation</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.micronaut.test</groupId>
<artifactId>micronaut-test-junit5</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-http-client</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-http-server-netty</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-runtime</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>javax.annotation</groupId>
<artifactId>javax.annotation-api</artifactId>
<scope>compile</scope>
</dependency>
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<scope>runtime</scope>
</dependency>
</dependencies>

<build>
<plugins>
<plugin>
<groupId>io.micronaut.build</groupId>
<artifactId>micronaut-maven-plugin</artifactId>
</plugin>

<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<!-- Uncomment to enable incremental compilation -->
<!-- <useIncrementalCompilation>false</useIncrementalCompilation> -->

<annotationProcessorPaths combine.children="append">
<path>
<groupId>io.micronaut</groupId>
<artifactId>micronaut-http-validation</artifactId>
<version>${micronaut.version}</version>
</path>
</annotationProcessorPaths>
<compilerArgs>
<arg>-Amicronaut.processing.group=org.knf.dev.demo</arg>
<arg>-Amicronaut.processing.module=helloworld</arg>
</compilerArgs>
</configuration>
</plugin>
</plugins>
</build>

</project>

Controller:

package org.knf.dev.demo.controller;

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

@Controller("/echo")
public class HelloWorld {

@Get
@Produces(MediaType.APPLICATION_JSON)
public String index() {
return "Hello World";
}
}

Application:

package org.knf.dev.demo;

import io.micronaut.runtime.Micronaut;

public class Application {

public static void main(String[] args) {
Micronaut.run(Application.class, args);
}
}

Execute the application in development mode:

mvn mn:run
 __  __ _                                  _   
|  \/  (_) ___ _ __ ___  _ __   __ _ _   _| |_ 
| |\/| | |/ __| '__/ _ \| '_ \ / _` | | | | __|
| |  | | | (__| | | (_) | | | | (_| | |_| | |_ 
|_|  |_|_|\___|_|  \___/|_| |_|\__,_|\__,_|\__|
  Micronaut (v3.1.1)

00:11:49.785 [main] INFO  io.micronaut.runtime.Micronaut - Startup completed in 4546ms. Server Running: http://localhost:8080


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