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reactive_programming_for_java_developers.pdf
- 1. Reactive Programming for JavaDevelopers Rossen Stoyanchev
- 2. About Me ❖ SpringFramework committer ❖ Spring MVC, WebSocket messaging ❖ Spring 5 Reactive
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- 4. 10 years ago Self-sufficientapps, 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 programmingmodel Imperative logic not so simple when latency is the norm Forced to deal with asynchronicity Limits of scale
- 7. There is anotherway Fundamentally async & non-blocking Using very few threads Major shift but also major benefits
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- 9. In this talk Howwould we design an async API in Java ? Can we do better ? Introducing reactive libraries Spring reactive experience
- 10. Design async APIin Java
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- 13. Return it asyncstyle ... May occur in different thread
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- 15. CompletableFuture (JDK 1.8) ❖Future with actions ❖ Actions trigger when Future completes ❖ Callback mechanism
- 16. Return it asyncstyle with Java 1.8 ... ...
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- 20. Return many ... ... Nocallback till all users collected
- 21. Return many ... ... Itmay be too many
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- 24. Can we dobetter?
- 25. ❖ One notificationper data item ❖ One notification for either completion or error Async results as a stream
- 26. Return Type DescriptionNotifications 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, declarativeprogramming model ➢ Combine, transform, reduce sequences ➢ Focus on what, not how Stream abstraction
- 28. ➢ Great exampleof the benefits of a stream API ➢ However built for collections mainly ➢ Pull-based, usable once Java 8 Stream
- 29. ➢ Latency-sensitive datastreams ➢ Infinite sequences ➢ Push-based notifications Beyond collections
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- 31. Reactive library? ➢ Stream-likeAPI similar to Java 8 ➢ Suited for any data sequence ➢ Latency-sensitive, infinite, collections
- 32. Project Reactor ➢ ReactiveStreams foundation for the JVM ➢ API similar to ReactiveX ➢ Easy to bridge to Java 8 Stream
- 33. Flux -- sequenceof 0..N
- 34. Mono -- sequenceof 0..1
- 35. Flux to JavaStream
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- 37. More than astream 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 bestfluent 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 injava.util.concurrent.Flow ❖ SubmissionPublisher standalone bridge to Reactive Streams ❖ Tie-ins to CompletableFuture and Stream Reactive Streams in Java 9
- 41. Reactive Streams API publicinterface Publisher<T> { void subscribe(Subscriber<? super T> subscriber); }
- 42. Reactive Streams API publicinterface Subscriber<T> { void onSubscribe(Subscription sub); void onNext(T item); void onError(Throwable ex); void onComplete(); }
- 43. Reactive Streams API publicinterface Subscriber<T> { void onSubscribe(Subscription sub); void onNext(T item); void onError(Throwable ex); void onComplete(); }
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- 45. Using the reactiverepository
- 46. Using the reactiverepository Subscriber triggers flow of data
- 47. Using the reactiverepository Consume all data by default
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- 49. Usage Consume two ata time
- 50. Output onSubscribe request(2) onNext(User: Jason) onNext(User: Jay) request(2) onNext(User:Joe) onNext(User: John) ...
- 51. ❖ Currently 2.5M4 (might change to 3.0 label) ❖ GA release scheduled for July ❖ Hands-on exercise, blog post series More on Reactor
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- 56. Spring MVC SpringWeb Reactive Annotated controllers
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- 59. Spring MVC SpringWeb Reactive Servlet API ??? @MVC
- 60. Spring MVC SpringWeb Reactive Servlet API ??? Servlet Container ??? @MVC
- 61. Spring Web Reactive @MVC HTTP ReactiveStreams Servlet 3.1 Reactor I/O RxNetty
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