reactive_programming_for_java_developers.pdf
- 1. Reactive Programming for Java Developers Rossen Stoyanchev
- 2. About Me ❖ Spring Framework committer ❖ Spring MVC, WebSocket messaging ❖ Spring 5 Reactive
- 4. 10 years ago Self-sufficient apps, App server, Keep it simple, don’t distribute Today Independent services, Cloud environment, Distributed apps
- 5. Changing expectations Internet scale & resilience, Efficient use of resources, Latency is common
- 6. Impact on programming model Imperative logic not so simple when latency is the norm Forced to deal with asynchronicity Limits of scale
- 7. There is another way Fundamentally async & non-blocking Using very few threads Major shift but also major benefits
- 9. In this talk How would we design an async API in Java ? Can we do better ? Introducing reactive libraries Spring reactive experience
- 10. Design async API in Java
- 12. Usage
- 13. Return it async style ... May occur in different thread
- 14. Usage Ugh
- 15. CompletableFuture (JDK 1.8) ❖ Future with actions ❖ Actions trigger when Future completes ❖ Callback mechanism
- 16. Return it async style with Java 1.8 ... ...
- 20. Return many ... ... No callback till all users collected
- 21. Return many ... ... It may be too many
- 24. Can we do better?
- 25. ❖ One notification per data item ❖ One notification for either completion or error Async results as a stream
- 26. Return Type Description Notifications void Success onComplete() void Failure onError(Throwable) User Match onNext(User), onComplete() User No match onComplete() User Failure onError(Throwable) List<User> Two matches onNext(User), onNext(User), onComplete() List<User> No match onComplete() List<User> Failure onError(Throwable)
- 27. ➢ Functional, declarative programming model ➢ Combine, transform, reduce sequences ➢ Focus on what, not how Stream abstraction
- 28. ➢ Great example of the benefits of a stream API ➢ However built for collections mainly ➢ Pull-based, usable once Java 8 Stream
- 29. ➢ Latency-sensitive data streams ➢ Infinite sequences ➢ Push-based notifications Beyond collections
- 31. Reactive library? ➢ Stream-like API similar to Java 8 ➢ Suited for any data sequence ➢ Latency-sensitive, infinite, collections
- 32. Project Reactor ➢ Reactive Streams foundation for the JVM ➢ API similar to ReactiveX ➢ Easy to bridge to Java 8 Stream
- 33. Flux -- sequence of 0..N
- 34. Mono -- sequence of 0..1
- 35. Flux to Java Stream
- 37. More than a stream API ➢ Reactor is back-pressure ready ➢ Reactive Streams spec ➢ Producers must not overwhelm consumers
- 38. ❖ Industry collaboration ❖ Small API, rules, TCK ❖ Reactive interoperability across libraries Reactive Streams Spec
- 39. “No single best fluent async/parallel API. CompletionStage best supports continuation-style programming on futures, and java.util.stream best supports (multi-stage, possibly- parallel) "pull" style operations on the elements of collections. Until now, one missing category was "push" style operations on items as they become available from an active source.“ Reactive Streams included in Java 9 Doug Lea, from initial announcement
- 40. ❖ Interfaces in java.util.concurrent.Flow ❖ SubmissionPublisher standalone bridge to Reactive Streams ❖ Tie-ins to CompletableFuture and Stream Reactive Streams in Java 9
- 41. Reactive Streams API public interface Publisher<T> { void subscribe(Subscriber<? super T> subscriber); }
- 42. Reactive Streams API public interface Subscriber<T> { void onSubscribe(Subscription sub); void onNext(T item); void onError(Throwable ex); void onComplete(); }
- 43. Reactive Streams API public interface Subscriber<T> { void onSubscribe(Subscription sub); void onNext(T item); void onError(Throwable ex); void onComplete(); }
- 45. Using the reactive repository
- 46. Using the reactive repository Subscriber triggers flow of data
- 47. Using the reactive repository Consume all data by default
- 49. Usage Consume two at a time
- 50. Output onSubscribe request(2) onNext(User: Jason) onNext(User: Jay) request(2) onNext(User: Joe) onNext(User: John) ...
- 51. ❖ Currently 2.5 M4 (might change to 3.0 label) ❖ GA release scheduled for July ❖ Hands-on exercise, blog post series More on Reactor
- 52. Reactive Spring
- 56. Spring MVC Spring Web Reactive Annotated controllers
- 57. ...
- 58. ... Mono<Object>
- 59. Spring MVC Spring Web Reactive Servlet API ??? @MVC
- 60. Spring MVC Spring Web Reactive Servlet API ??? Servlet Container ??? @MVC
- 61. Spring Web Reactive @MVC HTTP Reactive Streams Servlet 3.1 Reactor I/O RxNetty
- 64. Reactive Journey
- 65. @rstoya05