Micronaut Framework Cheatsheet

Micronaut is a modern, JVM-based framework designed for building modular and microservices-based applications. It boasts features like low memory consumption, fast startup times, and efficient use of resources. Whether you’re a seasoned Micronaut developer or just getting started, having a cheatsheet handy can be a great way to streamline your development process. In this cheatsheet, we’ll cover some key concepts and commands to accelerate your Micronaut development.

1. Getting Started

1.1 Create a Micronaut Project

mn create-app my-micronaut-app

1.2 Run the Application

./gradlew run

2. Controllers and Endpoints

2.1 Create a Controller

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

@Controller("/api")
public class MyController {

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

2.2 Path Variables

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

3. Dependency Injection

3.1 Inject a Bean

import javax.inject.Inject;

@Controller("/example")
public class ExampleController {

    @Inject
    private MyService myService;

    // Controller methods using myService
}

4. Configuration

4.1 Configuration Properties

my:
  property:
    value: 42

@Value("${my.property.value}")
private int myPropertyValue;

5. Data Persistence with JPA

5.1 Define an Entity

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Book {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String title;

    // Getters and setters
}

5.2 Repository Interface

import io.micronaut.data.annotation.Repository;
import io.micronaut.data.repository.CrudRepository;

@Repository
public interface BookRepository extends CrudRepository<Book, Long> {

    List<Book> findByTitle(String title);
}

6. Testing

6.1 Unit Testing with JUnit

import io.micronaut.test.extensions.junit5.annotation.MicronautTest;
import org.junit.jupiter.api.Test;

@MicronautTest
public class MyControllerTest {

    // Test methods
}

7. Logging

7.1 Log a Message

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Controller("/log")
public class LogController {

    private static final Logger LOG = LoggerFactory.getLogger(LogController.class);

    @Get("/message")
    public String logMessage() {
        LOG.info("This is a log message");
        return "Logged!";
    }
}

8. Security

8.1 Securing Endpoints

import io.micronaut.security.annotation.Secured;
import io.micronaut.security.rules.SecurityRule;

@Controller("/secure")
@Secured(SecurityRule.IS_AUTHENTICATED)
public class SecureController {

    // Secured methods
}

This Micronaut cheatsheet provides a quick reference for common tasks and concepts, helping you navigate the framework efficiently. Whether you’re working on controllers, configuring your application, or dealing with data persistence, this cheatsheet is a handy companion for your Micronaut development journey. Keep exploring and building with Micronaut to leverage its powerful features for creating robust and efficient applications.

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