Going Reactive with Spring (JugSaxonyDay 2017)

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ In a nutshell, reactive programming is about  non-blocking, event-driven applications  that scale with a small number of threads  with back pressure as a key ingredient  that aims to ensure producers to not overwhelm consumers. (Rossen Stoyanchev)

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The next 60 Minutes 3 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ - A bit of recent history. - Project Reactor / Spring Data Kay / Spring Framework 5. - Some Code.

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A bit of recent history. Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Sept 28 5.0 GA Dec 2017 Oct 2017 Kay GA 2.0 GA Sept 25 3.1 GA Sept 29 5.0 M1 Jul 2016 Kay M1 Sept 2016 Nov 2016 3.0 GA Sept 2015 Sept 21 9

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Imperative Applications 5 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ {…}

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Imperative Applications - Batching 6 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ {…} Batching

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Imperative Applications - Async 7 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ {…} Dispatcher Thread: Worker A Thread: Worker B Thread: Worker C

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Reactive Applications 8 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ {…} Subscriber Publisher Stream

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Reactive Applications 9 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ {…} Subscriber Publisher Stream .block()

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NoSQL for the win! 10 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/

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11 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Iterator.next() Future.get() Subscriber.onNext(t) Remember vs

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Reactor 3.1 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/

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Reactive Streams 13 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Provider of a potentially unbounded number of sequenced elements. Publisher Subscriber A processing stage - actually both a Subscriber and a Publisher. Processor One-to-one lifecycle of a Subscriber subscribing to a Publisher. Subscription

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14 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher Subscriber Processor Subscription .subscribe(Subscriber) .onSubscribe(Subscription) .request(long) .onNext(T) Reactive Streams

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No content

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Project Reactor 16 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher (0…n) Flux (0…n) Mono (0…1) Reactive Streams

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Project Reactor 17 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Publisher (0…n) Flux (0…n) Mono (0…1) Reactive Streams Mono findByEmail(String email); Flux findByName(String name); #jürgenized

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Flux 18 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ [fluhks] - a flowing or flow Flux.just("red", "white", "blue") .flatMap(v !-> Mono.fromCallable(blockingStuff(v)) .subscribeOn(Schedulers.elastic())) .collect(Result!::new, Result!::add) .doOnNext(Result!::stop) .subscribe(doWithResult);

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Mono 19 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ [mon-oh] - alone, single, one Mono.fromCallable(blockingStuff()) .map(v !-> unwarp(v)) .subscribe();

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Reactive Applications with Spring Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Spring Framework  5 Project Reactor  3.1 Spring Data  Kay

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Reactive Template (MongoDB) 22 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ /**  * Query for a {@link Flux} of objects of type T from the specified collection.  *  * @param entityClass the parametrized type of the returned {@link Flux}.  * @param collectionName name of the collection to retrieve the objects from  * @return the converted collection  */  Flux findAll(Class entityClass, String collectionName); /**  * Map the results of an ad-hoc query on the collection for the entity class to a   * single instance of an object of the  * specified type.   * @param query the query class that specifies the criteria   * @param entityClass the parametrized type of the returned {@link Mono}.  * @return the converted object  */  Mono findOne(Query query, Class entityClass);

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Reactive Repository 23 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Mono save(S entity); Mono save(Mono entity); Flux saveAll(Iterable entities); Flux saveAll(Publisher entities); Mono existsById(Mono id); Flux findAll(); Mono count(); Mono deleteById(ID id);

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Spring Data Reactive 24 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface Repo extends ReactiveCrudRepository { } Flux findAllByLastname(String lastname); Flux findAllByLastname(Mono lastname); Flux customQuery(String lastname); @Query("{lastname : ?0}"); Flux findAllByLastname(String ln, Pageable page);

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Spring WebFlux 25 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ @RestController  static class PersonController {    PersonRepository repository;              } @GetMapping("/")  Flux fluxPersons(String name) {  return repository.findAllByName(name);  } 

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Spring Data - Reactive Repository 27 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { } Flux.interval(Duration.ofSeconds(1))  .zipWith(starks)  .map(Tuple2!::getT2)  .flatMap(repository!::save)  .subscribe(); String[] names = { "Eddard", "Catelyn", "Jon", "Rob", "Sansa", "Aria", "Bran", "Rickon" };  Flux starks = Flux  .fromStream(Stream.generate(() !->   names[ramdom.nextInt(names.length)])  .map(Person!::new));

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Spring Data - Reactive Repository 28 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { } Flux.interval(Duration.ofSeconds(1))  .zipWith(starks)  .map(Tuple2!::getT2)  .flatMap(repository!::save)  .subscribe(); String[] names = { "Eddard", "Catelyn", "Jon", "Rob", "Sansa", "Aria", "Bran", "Rickon" };  Flux starks = Flux  .fromStream(Stream.generate(() !->   names[ramdom.nextInt(names.length-1)])  .map(Person!::new)); > cstrobl $ ./bin/mongo --port 52291 > use test switched to db test { "_id" : ObjectId("591009c5ed68a820fb9956a5"), "name" : "Sansa", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009c6ed68a820fb9956a6"), "name" : "Rob", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009c7ed68a820fb9956a7"), "name" : "Sansa", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009c8ed68a820fb9956a8"), "name" : "Rob", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009c9ed68a820fb9956a9"), "name" : "Jon", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009caed68a820fb9956aa"), "name" : "Aria", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009cbed68a820fb9956ab"), "name" : "Rob", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009cced68a820fb9956ac"), "name" : "Jon", "_class" : "com.example.DemoApplication$Person" } { "_id" : ObjectId("591009cded68a820fb9956ad"), "name" : "Sansa", "_class" : "com.example.DemoApplication$Person" } > db.person.find();

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Spring - WebFlux 29 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { Flux findAllByName(String name); } @RestController  static class PersonController {    PersonRepository repository;              } @GetMapping("/")  Flux fluxPersons(String name) {  return repository.findAllByName(name);  } 

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Spring - WebFlux 30 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { Flux findAllByName(String name); } @RestController  static class PersonController {    PersonRepository repository;              } @GetMapping("/")  Flux fluxPersons(String name) {  return repository.findAllByName(name);  }  > cstrobl $ curl localhost:8080/?name=Eddard | jq [ { "name": "Eddard", "id": "591014f2756bac231a23f3a0" }, { "name": "Eddard", "id": "591014f7756bac231a23f3a5" } ] >

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RxJava types 31 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { Observable findByName(String name); } @RestController  static class PersonController {    PersonRepository repository;    @GetMapping("/rx")  Observable rxPersons(String name) {  return repository.findByName(name);  }  }

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RxJava types 32 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { Observable findByName(String name); } @RestController  static class PersonController {    PersonRepository repository;    @GetMapping("/rx")  Observable rxPersons(String name) {  return repository.findByName(name);  }  } > cstrobl $ curl localhost:8080/rx?name=Rob | jq [ { "name": "Rob", "id": "590f6e99756bac18a8d62bfe" }, { "name": "Rob", "id": "590f6e9d756bac18a8d62c02" } { "name": "Rob", "id": "590f6e9e756bac18a8d62c03" } ] >

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Tailable Cursors & Event Stream 33 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { @Tailable Flux findBy(); } @RestController  static class PersonController {    PersonRepository repository;    @GetMapping(value = "/stream", produces = MediaType.TEXT_EVENT_STREAM_VALUE) Flux streamPersons() {  return repository.findBy();  }  }

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Tailable Cursors & Event Stream 34 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ interface PersonRepository extends ReactiveCrudRepository { @Tailable Flux findBy(); } @RestController  static class PersonController {    PersonRepository repository;    @GetMapping(value = "/stream", produces = MediaType.TEXT_EVENT_STREAM_VALUE) Flux streamPersons() {  return repository.findBy();  }  } > cstrobl $ curl localhost:8080/stream data:{"name":"Sansa","id":"5910192e756bac26079dd623"} data:{"name":"Jon","id":"5910192f756bac26079dd624"} data:{"name":"Catelyn","id":"59101930756bac26079dd625"} data:{"name":"Eddard","id":"59101931756bac26079dd626"} data:{"name":"Jon","id":"59101932756bac26079dd627"} data:{"name":"Eddard","id":"59101933756bac26079dd628"}

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WebFlux - Router Functions 35 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ @Component  static class PersonHandler { PersonRepository repository; Mono streamPersons(ServerRequest request) { return ServerResponse.ok()  .contentType(MediaType.TEXT_EVENT_STREAM)  .body(personRepository.findBy(), Person.class); } @Bean  RouterFunction routes(PersonHandler requestHandler) {   return RouterFunctions  .route(RequestPredicates.GET("/stream"), requestHandler!::streamPersons) }

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Spring - WebClient 36 Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ @Bean  WebClient client() {  return WebClient.create("http:!//localhost:8080/");  }    @Bean  CommandLineRunner run(WebClient client) {    return (args) !-> {    client.get()  .uri("/stream")  .retrieve()  .bodyToFlux(Person.class)  .subscribe(System.out!::println);  };  }

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Unless otherwise indicated, these slides are © 2013-2017 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive is about efficient resource usage. Even if backed with familiar concepts and framework support,   it is no free lunch. The price is complexity.