Reactive Spring 5 Reactive Programming with Spring WebFlux and Spring Data Corneil du Plessis 

A defnition reactive programming is an asynchronous programming paradigm concerned with data streams and the propagation of change Wikipedia 

Reactive Manifesto • Responsive • Resilient • Elastic • Message Driven 

Why reactive programming? • Handle back-pressure • Communicate change • Scalability • Performance • Reliability 

Reactive Programming Models • Windows API • JVM Based • NIO • LMAX Disruptor • Akka Actor Model • JavaScript • AJAX • Promises • jQuery • Angular • React • FRP – Functional Reactive Programming • map, reduce, flter • Languages not limited to: • Scala • Kotlin • Haskell • Elm • Groovy • JavaScript • Java 8 

Road to Reactive Spring • RxJava – 2011-2012 by Netfix • Project Reactor – 2013 by Pivotal • Reactive Streams Specifcation – 2014 collaboration by Netfix, Pivotal, Red Hat, Twitter, Typesafe and more. • reactor-spring • Spring 5 

Implementing Technologies HttpHander / WebHander API • Netty • Undertow • Tomcat with Servlet 3.1 • Jetty with Servlet 3.1 Reactive Databases • MongoDB Reactive Streams Driver • Reactive Cassandra (RxJava) • Lettuce (Reactive Streams for Redis) • Reactive Couchbase. 

Reactive Streams specifcation • Publisher • Subscriber • Subscription • Processor 

Reactive Streams – Sequence Diagrams Subscribe Publish 

Project Reactor • Implements Reactive Streams specifcation • Infuenced by RxJava • Infuenced by Java 8 Streams • Improved Developer Experience • Mono - 0 or One • Flux - 0 or More 

Project Reactor - Mono static Mono just(T data); static Mono fromFuture( CompleteableFuture); Mono log(String category); T block(); T block(Duration timeout); map, flatMap, filter 

Project Reactor - Flux static Flux just(T data); static Flux just(T … data); static Flux fromStream(Stream s); static Flux fromIterable i); Flux log(String category); static Mono> collectList(); Mono next(); Iterable toIterable(); Stream toStream(); map, flatMap, filter, reduce 

Reactive Spring WebFlux • Annotated Controllers • @Controller or @RestController • @RequestMapping / @GetMapping / @PostMapping etc. • Flux instead of Collection • Functional Endpoints • Router Function • Handler Function • HandlerFilter Function 

Spring MVC @RestController public class HistoryController { private HistoryInterface locHist; public HistoryController(HistoryInterface locHist) { this. locHist = locHist; } @GetMapping(path = "/search") public Collection find( @RequestParam("startDate") Date startDate, @RequestParam("endDate") Date endDate) { return locHist.find(startDate, endDate); } } 

Reactive Spring WebFlux @RestController public class HistoryController { private HistoryInterface locHist; public HistoryController(HistoryInterface locHist) { this. locHist = locHist; } @GetMapping(path = "/search") public Flux find( @RequestParam("startDate") Date startDate, @RequestParam("endDate") Date endDate) { return locHist.find(startDate, endDate); } } 

Reactive Spring WebFlux (Functional Endpoint) public class HistoryHandler { private HistoryInterface locHist; public History HistoryHandler( HistoryInterface locHist) { this. locHist = locHist; } public Mono find(ServerRequest request) { Date startDate = DateUtils.from(request.queryParam("startDate")); Date endDate = DateUtils.from(request.queryParam("endDate")); return ServerResponse.ok() .contentType(APPLICATION_JSON) .body(locHist.find(startDate, endDate), LocationHistory.class); } } 

Reactive Spring WebFlux (Functional Endpoint) @Configuration @EnableWebFlux public class HistoryConfiguration { @Autowire private HistoryHandler histHandler; @Bean RouterFunction router() { return route(GET("/search") .and(accept(APPLICATION_JSON)), histHandler::find); } } 

Spring Data public interface LocationHistoryRepository extends CrudRepository { Collection findByTimestampBetween( Date s, Date e); } 

Reactive Spring Data public interface LocationHistoryRepository extends ReactiveCrudRepository { Flux findByTimestampBetween( Date s, Date e); } 

Spring Data JPA • Spring Data JPA does not have Reactive Support. • Streams will provide best experience until reactive JDBC and JPA is available. // Repository method Stream findByDateBetween( Date startDate, Date endDate); // Service method return Flux.fromStream(repository.findByDateBetween(s,e)); 

Demo Non-reactive • Spring Boot 1.5.8 • Spring MVC • Spring Data MongoDB Reactive • Spring Boot 2.0.3 • Spring WebFlux • Spring Data Reactive MongoDB 

Call timing Non-reactive • 0.000 >> controller • 0.000 >> service • 0.409 << service • 0.409 << controller Reactive • 0.000 >> controller • 0.000 >> service • 0.001 << service • 0.001 << controller 

Synchronous process 

Asynchronous process 

Network timing Non-reactive Type Time Name lookup 0.004 Connect 0.005 Pre transfer 0.005 Start Transfer 0.419 Total 0.532 Reactive Type Time Name lookup 0.004 Connect 0.005 Pre transfer 0.005 Start Transfer 0.385 Total 0.425 

WebFlux vs Servlet 

More aspects of Reactive Programming • Error handling • Back pressure • Retry • Timeouts • Transactions 

Thoughts on Reactive Spring • Pros • Great documentation • Preserves program structure • Safer concurrency • Simpler abstraction than RxJava without sacrifcing the power. • Facilitates good practice • Kotlin support in Core • Cons • Debugging complexity • Could not fnd any other negative comments 

See Also • ReactiveX • Languages • RxJava • RxKotlin • RxGroovy • RxClojure • RxSwift • Rx.Net (C#) and more… • Platforms • RxAndroid • RxCocoa • RxNetty • Akka & Akka Streams • Ratpack • Vert.x • Play Framework • Languages • Reactor Scala Extensions • Reactor Kotlin Extensions (now in core) • Messaging Communication • Reactor Kafka • Reactor RabbitMQ • Reactor Aeron • Reactor Netty 

Finally • Contact: @corneil • Source - https://github.com/corneil/reactive-spring-5 • Resources • Project Reactor Site - https://projectreactor.io/ • David Karnok's Blog - http://akarnokd.blogspot.co.za/ • WebFlux vs Servlet https://dzone.com/articles/raw-performance-numbers-spring-boot-2-webfux-vs-s Questions? 

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