Lesson 8: GraalVM with Quarkus – Mutiny and RESTEasy .

Lesson 8: GraalVM with Quarkus – Mutiny and RESTEasy
This lesson explores the integration of GraalVM in Quarkus with a focus on Mutiny for reactive programming and RESTEasy for building RESTful APIs.

Mutiny Integration: 4 Key Points

1. Reactive Programming with Mutiny
   Mutiny is Quarkus's reactive programming library that simplifies asynchronous workflows. It provides a developer-friendly API for handling streams and events, ensuring scalability and performance in reactive applications built on GraalVM.

2. Non-Blocking I/O
   Mutiny leverages non-blocking I/O to handle high-concurrency workloads efficiently. This is crucial in cloud-native applications where scaling horizontally with minimal resource use is vital. GraalVM’s native image ensures these reactive operations are lightweight and fast.

3. Event-Driven Architecture
   Mutiny supports event-driven designs, allowing developers to react to data streams and user actions dynamically. Its integration with GraalVM-optimized Quarkus applications ensures low latency and high throughput, suitable for real-time systems.

4. Simplified Error Handling
   Mutiny includes intuitive error-handling methods such as onFailure() and recoverWith(). This reduces complexity when managing failures in asynchronous flows, making applications more resilient while maintaining high performance.

Examples for Mutiny

1. Reactive Service with Mutiny

@ApplicationScoped
public class ReactiveService {
    public Uni<String> getData() {
        return Uni.createFrom().item("Hello, Mutiny!")
                  .onItem().transform(String::toUpperCase);
    }
}

This creates a reactive service that transforms a string asynchronously.

2. Error Recovery with Mutiny

public Uni<String> fetchData() {
    return Uni.createFrom().failure(new RuntimeException("Error"))
              .onFailure().recoverWithItem("Default Data");
}

This handles a failure by providing default data, ensuring the application remains responsive.

RESTEasy Integration: 2 Key Points

1. Efficient RESTful APIs
   RESTEasy, integrated into Quarkus, enables developers to build lightweight REST APIs. With GraalVM, REST endpoints benefit from fast startup times and minimal resource use, ideal for microservices.

2. Reactive REST with RESTEasy Reactive
   RESTEasy Reactive allows building non-blocking REST APIs that handle high concurrency efficiently. Combined with GraalVM, these APIs achieve low latency and optimal performance for cloud-native deployments.

Examples for RESTEasy

1. Basic REST Endpoint

@Path("/hello")
public class HelloResource {
    @GET
    public String hello() {
        return "Hello, RESTEasy!";
    }
}

This defines a simple REST endpoint.

2. Non-Blocking REST Endpoint

@Path("/data")
public class DataResource {
    @GET
    public Uni<String> getData() {
        return Uni.createFrom().item("Hello from Reactive REST!");
    }
}

This demonstrates a non-blocking REST endpoint using RESTEasy Reactive and Mutiny.