Introduction to Micronaut with Java

What is Micronaut?

The concept of the Micronaut Foundation stems from the real-time exchange of quality information in the field of building physics, from monoliths to microservices, using the perspective of Spring, Spring Boot, and Grails. With the help of the Micronaut Foundation, the Essential team built and maintained the Micronaut project.

• It is created by the OCI team, headed by Graeme Roecher
• 1.0 released in 2018
• Open-sourced in May 2018
• Inspired other frameworks to improve and new frameworks to be born on the same approach
• Latest release 4.5.3

The Micronaut organization aims to demonstrate all specific practices in JVM design:

• Dependency Injection and Inversion of Control (IoC)
• Aspect Oriented Programming (AOP)
• Sensible Defaults and Auto-Configuration

The following resources are provided by the Micronaut Foundation to address the shortcomings of the Spring, and Grails foundations.

• Fast startup period
• Reduced thought footmark
• Minimal use of impression
• No runtime bytecode creation
• Easy Unit Testing

This aim is realized through the use of Java’s annotation processors, that are working on some JVM style that supports bureaucracy, in addition to an HTTP Server (accompanying various runtimes Undertow, Tomcat, Jetty, Netty…​)and an HTTP client (with multiple runtimes Java HTTP Client, Netty, …​).

Key Features of Micronaut

1. Compile-Time Dependency Injection (DI): Micronaut performs dependency injection at compile time, unlike traditional Java programs that use runtime images. This approach eliminates the performance overhead associated with images, resulting in faster start-up times and reduced memory consumption.
2. Ahead of Time (AOT) Compilation: Micronaut uses AOT compilation to pre-calculate most application configurations and wiring. This results in efficient and high-quality applications that are ready to run as soon as they are deployed.
3. Functional applications: Micronaut’s responsive operating system provides robust support, enabling users to create scalable concurrent applications. With built-in support for libraries like Reactor and RxJava, Micronaut makes it easy to use responsive modeling in your applications.
4. Minimal Configuration: With practical defaults and minimum boilerplate code, Micronaut makes it smooth to get started and reduces the overhead related to utility configuration.
5. Interoperability: Micronaut integrates seamlessly with existing Java libraries and frameworks, ensuring that builders can leverage their existing knowledge and codebase while adopting Micronaut.
6. Simplified testing skills: Testing is a crucial issue of software program development and Micronaut stands proud on this subject with its simplified checking out talents. By presenting an integrated guide for unit, integration, and stop-to-end testing, Micronaut empowers developers to write strong tests that ensure the reliability and balance of their applications.
7. Lightning-Fast Start-up Time: One of the standout functions of Micronauts is its lightning-speedy start-up time. Unlike many different frameworks that may be slow to initialize, Micronaut boasts a remarkable pace, permitting builders to get up and strolling in a count of milliseconds.
8. Modular Architecture: Micronaut’s modular architecture permits you to select and pick out the functions you need, resulting in a lightweight and green application. This modularity additionally makes it easy to increase the framework with custom modules as needed.

Benefits of Using Micronaut

1. Performance: Compile-time DI and AOT compilation methods used by Micronaut provide significant performance improvements. Applications developed with Micronaut launch faster and consume less memory than applications developed with traditional Java frameworks. This is especially beneficial for microservices and serverless applications, where fast start-up times and resource efficiency are important.
2. Flexibility: Micronaut is a versatile framework suitable for various applications. Whether you are building microservices, server-less tasks, or traditional web applications.
3. Interoperability: Micronaut is designed to work seamlessly with existing Java libraries and programs.
4. Cloud-native Design: Micronaut was designed from the start to support cloud-native development. With built-in features for usage discovery, distributed analytics, and cloud deployment, Micronaut simplifies the process of building and deploying microservices in a cloud environment this native cloud supports the developers so that they can concentrate on fixing the problems because they don’t have to worry about infrastructure.
5. Developer Productivity: Micronaut’s minimalist approach to programming and its use of logical pre-sets makes it easy to get started. Developers can quickly build and deploy applications without complicated configuration files or boilerplate code.

Setting your own development environment

Before we dive into the Micronaut application, let’s set up our development environment.

Prerequisites
Java 8 or more
Gradle or Maven
IDE (Eclipse, IntelliJ IDEA, etc.) .

1. Install Micronaut Command-Line Interface (CLI): Micronaut offers a CLI tool(you can use SDKMAN) to streamline the process of creating and handling tasks.
2. Micronaut Launch: if the CLI is not installed, you can create the same application by visiting Micronaut Launch.
3. Setting up an IDE: https://docs.micronaut.io/snapshot/guide/#ideSetup

Basic Annotations

@Controller- In Micronaut, a class is defined as a controller using the @Controller annotation. It routes HTTP requests to the proper channels after processing them.

@Controller("/first")
public class FirstController {

@Get("/")
public String firstService() {
return "First Micronaut Service.";
}

}

@Inject- In Micronaut, the @Inject annotation is used to set dependencies in your classes.

@Controller("/service")
public class ServiceController {

@Inject
private MyService myService;

}

@Singleton- In Micronaut, using the @Singleton annotation indicates that a bean instance should be created and shared.

@Singleton
public class MyService {
// Some service logic
}

@Value- In Micronaut, the @Value annotation is used to inject configuration properties.

@Singleton
public class ConfigService {

@Value("${myapp.message}")
private String message;

public String getMessage() {
return message;
}

}

@Requires- In Micronaut, the @Requires annotation is used to conditionally enable a bean based on certain conditions, like the presence of a property.

@Singleton
@Requires(property = "myapp.enabled", value = "true")
public class MyService {
// Service logic
}

@Property- In Micronaut, the @Property annotation is used to bind configuration properties to a class.

@Singleton
@Property(name = "myapp.service")
public class MyAppService {

private final String name;

public MyAppService(@Property(name = "myapp.service.name") String name) {
this.name = name;
}

public String getName() {
return name;
}

}

@Client- In Micronaut, the @Client annotation is used to create a declarative HTTP client.   

@Client("/external")
public interface ExternalClient {

@Get("/data")
String getData();

}

@EventListener- In Micronaut, the @EventListener annotation is used to mark a method as an event listener.

@Singleton
public class MyEventListener {

@EventListener
public void onEvent(Event event) {
// event logic
}

}

@Filter- In Micronaut, the @Filter annotation is used to define a filter for HTTP requests.

@Filter("/api/**")
public class CustomFilter implements HttpServerFilter {

@Override
public Publisher<HttpResponse<?>> doFilter(HttpRequest<?> request, ServerFilterChain chain) {
// Filtering logic
return chain.proceed(request);
}

}

For More Annotations — https://micronaut-projects.github.io/micronaut-data/latest/guide/#shared

Source Code — https://github.com/Akash1691/employee-management-service

Conclusion 

Micronaut is a significant advancement in the development of the Java framework. Its emphasis on functionality, simplicity, and contemporary application development positions it as a preferred option for developers seeking enhanced power and performance. With Micronaut, you can leverage the full power of Java with the performance gains normally associated with low-level systems.

Whether you’re building microservices, server less applications, or traditional web applications, Micronaut provides a robust and efficient platform to build on. Start exploring Micronaut today and get Java application development in the future!

References:

Micronaut Guide —  https://redis.io/docs/getting-started/installation/

Miconaut Webinars — https://www.youtube.com/watch?v=Fn_Yac_NReE&list=PLzR4N8lGQvWiNW17TfJ2tksWFjjKJbbqZ&index=26