Functional Reactive Endpoints using Spring 5
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The document discusses the concepts of reactive programming and functional reactive programming (FRP) as implemented in Spring 5, emphasizing their advantages like non-blocking applications and efficient scaling. It provides an overview of key components such as observers, streams, and back-pressure, as well as the implementation of reactive repositories and REST endpoints in a sample code. Additionally, it outlines both the benefits and challenges of adopting reactive programming, including issues related to debugging and the learning curve.
![Angular
quotes: Quote[] = new Array();
url: string = 'http://localhost:8080/quotes-reactive';
getQuoteStream(page?: number, size?: number): Observable<Array<Quote>> {
this.quotes = new Array();
return Observable.create((observer) => {
let url = this.url;
let eventSource = new EventSource(url);
eventSource.onmessage = (event) => {
console.debug('Received event: ', event);
let json = JSON.parse(event.data);
this.quotes.push(new Quote(json['id'], json['book'], json['content']));
observer.next(this.quotes);
};
eventSource.onerror = (error) => observer.error('EventSource error: ' + error);
});
}](https://image.slidesharecdn.com/reactive-180131104332/85/Functional-Reactive-Endpoints-using-Spring-5-13-320.jpg)
![Angular
quotes: Quote[] = new Array();
url: string = 'http://localhost:8080/quotes-reactive';
getQuoteStream(page?: number, size?: number): Observable<Array<Quote>> {
this.quotes = new Array();
return Observable.create((observer) => {
let url = this.url;
let eventSource = new EventSource(url);
eventSource.onmessage = (event) => {
console.debug('Received event: ', event);
let json = JSON.parse(event.data);
this.quotes.push(new Quote(json['id'], json['book'], json['content']));
observer.next(this.quotes);
};
eventSource.onerror = (error) => observer.error('EventSource error: ' + error);
});
}](https://image.slidesharecdn.com/reactive-180131104332/85/Functional-Reactive-Endpoints-using-Spring-5-14-320.jpg)
Functional Reactive Endpoints using Spring 5
- 1. Reactive Spring 5 (AKA Functional Reactive Programming with Spring)
- 2. Why I chose this talk?
- 3. A definition Reactive Programming is all about non-blocking applications that are asynchronous and event-driven and require a small number of threads to scale -Spring.io
- 4. What is Reactive Programming? • Observer • Interface to notify an object that the next item in a sequence it is watching it is available • Streams • Controlled exchange of stream data across Applications • Back-pressure • control the flow of a Stream between producer and consumer
- 6. What is Functional Reactive Programming? Conal Elliot defined FRP back in 1998, in his paper "Functional Reactive Animation”: • “FRP expressions describe entire evolutions of values over time, representing these evolutions directly as first-class values
- 7. What is Functional reactive programming? • Compositionality • Being able to compose functions • Immutability • Guarantees inherently parallelisable
- 10. Reactive Mongo public interface QuoteMongoReactiveRepository extends ReactiveCrudRepository<Quote, String> { }
- 12. Reactive Rest @GetMapping("/quotes-reactive") public Flux<Quote> getQuoteFlux() { return quoteMongoReactiveRepository.findAll(); }
- 13. Angular quotes: Quote[] = new Array(); url: string = 'http://localhost:8080/quotes-reactive'; getQuoteStream(page?: number, size?: number): Observable<Array<Quote>> { this.quotes = new Array(); return Observable.create((observer) => { let url = this.url; let eventSource = new EventSource(url); eventSource.onmessage = (event) => { console.debug('Received event: ', event); let json = JSON.parse(event.data); this.quotes.push(new Quote(json['id'], json['book'], json['content'])); observer.next(this.quotes); }; eventSource.onerror = (error) => observer.error('EventSource error: ' + error); }); }
- 14. Angular quotes: Quote[] = new Array(); url: string = 'http://localhost:8080/quotes-reactive'; getQuoteStream(page?: number, size?: number): Observable<Array<Quote>> { this.quotes = new Array(); return Observable.create((observer) => { let url = this.url; let eventSource = new EventSource(url); eventSource.onmessage = (event) => { console.debug('Received event: ', event); let json = JSON.parse(event.data); this.quotes.push(new Quote(json['id'], json['book'], json['content'])); observer.next(this.quotes); }; eventSource.onerror = (error) => observer.error('EventSource error: ' + error); }); }
- 15. Demo Time
- 16. How do you test? • curl -H "Accept: text/event-stream" http://localhost:8080/quotes-reactive • Spring WebClient • Spring WebTestClient • Postman? Soapui? Browser?
- 17. Thoughts on Reactive Spring • Pros • Safer concurrency • scale with a small, fixed number of threads and less memory. • makes applications more resilient under load because they scale in a more predictable way • Baked into Spring • Java 10 Oracle Drivers Planned
- 18. Thoughts on Reactive Spring • Cons • Debugging complexity • Steeeeeeep learning curve • Do we understand Blocking? • “it doesn’t matter if you use a Reactive Web approach in the backend, it won’t be really reactive and non-blocking unless your client is able to handle it as well”
- 19. Finally • Source - https://github.com/roryp/full-reactive-stack • Resources • Project Reactor Site - https://projectreactor.io/ • Conal’s original paper https://github.com/conal/talk-2015-essence-and- origins-of-frp