Reactive Spring

This session will start with a Reactive Streams and Reactive APIs introduction, then will show concretely how you can build a reactive application using Spring 5.0, Spring Boot 2.0 and Java 8 with code and demos including a JSON REST API, Mustache templates based HTML rendering with Server-Sent Events push for live updates. We will also cover how to use Spring Data Reactive and the new ‘WebClient’ for processing data coming from remote services (REST or streaming APIs). Netty will be used as the underlying non-blocking HTTP engine for both client and server. I will also give you an overview of the Spring WebFlux functional Web API based on lambdas instead of annotation and of Spring 5.0 Kotlin native support.

Transcript

1. Reactive Spring Sébastien Deleuze - @sdeleuze Brian Clozel - @bclozel
3. 2 ∞
4. 2 ∞
5. 2 ∞
6. 2 ∞
7. Blocking + Thread pools 3 HTTP request HTTP response ⏳ ⚙ ⏳ ✍ ⏳ Thread
8. Non-blocking and event-loop 4 IO Selector Thread Worker Threads ⚙ ⚙ ✍ ✍ ⚙ ⚙ ✍ ✍ ⚙ ⚙ ✍
9. 5 From blocking to event-based Neutral to latency
10. 6 Reactive Foundations
11. 7 Going Reactive More for scalability and stability than for speed
12. Reactive Streams 8 Publisher Subscriber
13. Reactive Streams 8 Publisher Subscriber subscribe
14. Reactive Streams 8 Publisher Subscriber request(n) Backpressure
15. Reactive Streams 8 Publisher Subscriber Backpressure onNext(data) onNext(data) onNext(data)
16. Reactive Streams 8 Publisher Subscriber Backpressure Error|Complete
17. 9 public interface Publisher<T> { void subscribe(Subscriber<? super T> s); } public interface Subscriber<T> { void onSubscribe(Subscription s); void onNext(T t); void onError(Throwable t); void onComplete(); } public interface Subscription { void request(long n); void cancel(); } public interface Processor<T, R> extends Subscriber<T>, Publisher<R> { } Reactive Streams API
18. 10 Reactive Streams based libraries:
19. 10 Reactive Streams based libraries: RxJava Reactor Akka Streams
20. 11 Reactor is a reactive API based on reactive streams and Java 8
21. 12 Flux<T> Mono<T>
22. 13 Flux<T> is a Publisher<T> for 0..n elements
23. 14 Flux<T> Mono<T>
24. 15 Mono<T> is a Publisher<T> for 0..1 element
25. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message));
26. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); Mono<Weather> fetchWeather(String city);
27. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); times out and emits an error after 2 sec
28. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); logs a message in case of errors
29. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); switches to a different service in case of error
30. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); transforms a weather instance into a String message
31. 16 String location = "Lyon, France"; mainService.fetchWeather(location) .timeout(Duration.ofSeconds(2)) .doOnError(ex -> logger.error(ex.getMessage())) .onErrorResume(ex -> backupService.fetchWeather(location)) .map(w -> String.format("Weather in %s is %s", w.getLocation(), w.getDescription())) .subscribe(message -> logger.info(message)); triggers the processing of the chain
32. 17 Building Reactive applications
33. 18 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } interface UserRepository { User findOne(String id); List<User> findAll(); void save(User user); } Blocking API Reactive API
34. 19 interface UserRepository { User findOne(String id); List<User> findAll(); void save(User user); } Blocking API
35. 19 interface UserRepository { User findOne(String id); List<User> findAll(); void save(User user); } Blocking API Method returns when whole list is received
36. 19 interface UserRepository { User findOne(String id); List<User> findAll(); void save(User user); } Blocking API Throws exception if an error happens
37. 20 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } interface UserRepository { User findOne(String id); List<User> findAll(); void save(User user); } Blocking API Reactive API
38. 21 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } Reactive API
39. 21 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } Reactive API Method returns immediately!
40. 21 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } Reactive API Elements are received as soon as they are available, ending with a success "onComplete" event.
41. 21 interface ReactiveUserRepository { Mono<User> findOne(String id); Flux<User> findAll(); Mono<Void> save(Mono<User> user); } Reactive API Mono<Void> means error or success,
 no data will be received
42. 22 Flux<T>: Async collection vs. Stream of data
43. 23 Flux<User>
44. 24 Flux<User> as a JSON array
45. 24 GET /users … 200 OK
 Content-Type: application/json [ {"a": "foo", "b": "bar"}, {"a": "baz", "b": "boo"} ] Flux<User> as a JSON array
46. 25 Flux<User> as Server Sent Events
47. 25 GET /users … 200 OK
 Content-Type: text/event-stream data: {"a": "foo", "b": "bar"} data: {"a": "baz", "b": "boo"} data: {"a": "dev", "b": "oxx"} data: {"a": "spr", "b": "ing"} data: {"a": "lov", "b": "es"} data: {"a": "and", "b": "more"} data: {"a": "data", "b": "coming"} Flux<User> as Server Sent Events
48. 26 Flux<User> as a JSON stream
49. 26 GET /users … 200 OK
 Content-Type: application/stream+json {"a": "foo", "b": "bar"} {"a": "baz", "b": "boo"} {"a": "dev", "b": "oxx"} {"a": "spr", "b": "ing"} {"a": "lov", "b": "es"} {"a": "and", "b": "more"} {"a": "data", "b": "coming"} Flux<User> as a JSON stream
50. 27 Reactive Spring
51. 28 Spring Framework 5 uses Reactor for its reactive foundations
54. 30 With Reactive Spring, you can use your reactive library of choice for your application:
55. 30 With Reactive Spring, you can use your reactive library of choice for your application: RxJava Reactor Akka Streams
56. 31 Reactor
57. 31 Reactor
59. 32 @Controller, @RequestMapping Spring MVC Servlet API Servlet Container
60. 32 @Controller, @RequestMapping Spring MVC Servlet API Servlet Container Servlet 3.1, Netty, Undertow Spring WebFlux HTTP / Reactive Streams
61. 32 @Controller, @RequestMapping Spring MVC Servlet API Servlet Container Router functions Servlet 3.1, Netty, Undertow Spring WebFlux HTTP / Reactive Streams
62. 33 Flux<Tweet> WebClient Streaming API
63. 33 Flux<Tweet> ✔ Reactive API ✔ Can consume (infinite) streams WebClient Streaming API
64. 34 Flux.zip(tweets, issues) WebClient Streaming API REST API WebClient
65. 34 Flux.zip(tweets, issues) ✔ Chain and compose WebClient Streaming API REST API WebClient
66. 35 WebClient Web handler WebFlux
67. 36 WebClient Web handler WebFlux
68. 36 WebClient Web handler WebFlux ✔ Shared resources (event loop, buffers) ✔ Built-in mocking capabilities
69. 37 WebClient, a nice RestTemplate alternative
70. 37 WebClient, a nice RestTemplate alternative ✔ Fluent and flexible API ✔ Easy configuration
71. 38 WebFlux demo!
72. 39 https://github.com/bclozel/webflux-streaming-showcase quote-stream streaming-service GET /quotes
 "application/stream+json" GET /quotes/feed
 "text/event-stream" MongoDB
73. 40 WebFlux, the functional way
74. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction

75. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction
 Mono<HandlerFunction<ServerResponse>> route(ServerRequest req)
76. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction
 boolean test(ServerRequest req)
77. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction
 Mono<ServerResponse> handle(ServerRequest req)
78. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction
 Mono<ServerResponse> filter(ServerRequest req,
 HandlerFunction<ServerResponse> next)
79. 41 ‣ RouterFunction
 ‣ RequestPredicate
 ‣ HandlerFunction
 ‣ HandlerFilterFunction

80. 42 // Annotation-based Java @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE) public Flux<Quote> fetchQuotesStream() { ... }
81. 43 // Annotation-based Java @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE) public Flux<Quote> fetchQuotesStream() { ... } route( // Functional Java without static imports RequestPredicates. RequestPredicates.accept(TEXT_EVENT_STREAM)), path( ) { ... } ) .and( "/quotes/feed" RouterFunctions.
82. 44 // Annotation-based Java @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE) public Flux<Quote> fetchQuotesStream() { ... } accept(TEXT_EVENT_STREAM)), path( ) { ... } ) .and( "/quotes/feed" // Functional Java with static imports route(
83. 45 // Annotation-based Java @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE) public Flux<Quote> fetchQuotesStream() { ... } accept(TEXT_EVENT_STREAM) { ... } and "/quotes/feed" // Functional Kotlin router { }
84. 46 @RestController public class UserController { @GetMapping( ) public Flux<User> () { // ... } @GetMapping( ) public Mono<User> (@PathVariable String userId) { // ... } } fetchAll "/users" "/users/{id}" fetch
85. 47 @Configuration class ApplicationRoutes(val userHandler: UserHandler, val blogHandler: BlogHandler, val shopRepository: ShopRepository) { @Bean fun appRouter() = router { GET( , userHandler:: ) GET( , userHandler:: ) } } fetchAll "/users" "/users/{id}" fetch @Bean fun nestedRouter() = router { @Bean fun dynamicRouter() = router { ... ... } }
86. 48 @Bean fun nestedRouter() = router { @Bean fun dynamicRouter() = router {... } } ("/blog" and accept(TEXT_HTML)).nest { GET("/", blogHandler::findAllView) GET("/{slug}", blogHandler::findOneView) } ("/api/blog" and accept(APPLICATION_JSON)).nest { GET("/", blogHandler::findAll) GET("/{id}", blogHandler::findOne) POST("/", blogHandler::create) }
87. 49 @Bean fun dynamicRouter() = router { } shopRepository.findAll() .toIterable() .forEach { shop -> GET("/${shop.id}") { req -> shopHandler.homepage(shop, req) } }
88. 50 Spring ❤ Kotlin
90. 52 inline fun <reified T : Any> ServerResponse.BodyBuilder.body(publisher: Publisher<T>) = body(publisher, T::class.java) ServerResponse extensions provided in spring-webflux.jar
91. 52 inline fun <reified T : Any> ServerResponse.BodyBuilder.body(publisher: Publisher<T>) = body(publisher, T::class.java) ServerResponse extensions provided in spring-webflux.jar Extend existing Spring Java type
92. 52 inline fun <reified T : Any> ServerResponse.BodyBuilder.body(publisher: Publisher<T>) = body(publisher, T::class.java) ServerResponse extensions provided in spring-webflux.jar Extend existing Spring Java type Mono<ServerResponse> findAll(ServerRequest request) { return ServerResponse.ok().body(repository.findAll(), User.class); } Need to specify the type because of type erasure
93. 52 fun findAll(req: ServerRequest) = ok().body(repository.findAll()) No need to specify explicitly types thanks
 to Kotlin reified type parameters inline fun <reified T : Any> ServerResponse.BodyBuilder.body(publisher: Publisher<T>) = body(publisher, T::class.java) ServerResponse extensions provided in spring-webflux.jar Extend existing Spring Java type
94. 53 Kotlin extensions bundled with Spring 5
95. 53 Kotlin extensions bundled with Spring 5 Reactor (via reactor-kotlin-extensions) ApplicationContext WebFlux client WebFlux server Spring MVC RestTemplate JDBC Spring Data extensions are coming
96. 54 start.spring.io
97. 55 start.spring.io
98. 56 Thank You!