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
   

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3. 2
   ∞
   

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4. 2
   
   ∞
   

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5. 2
   
   
   ∞
   

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6. 2
   
   
   ∞
   

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7. Blocking + Thread pools
   3
   HTTP request
   HTTP response
   
   ⏳
   ⚙
   ⏳
   ✍
   ⏳
   Thread
   

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8. Non-blocking and event-loop
   4
   IO Selector Thread Worker Threads
   
   
   ⚙ ⚙ ✍
   ✍ ⚙
   ⚙
   ✍ ✍ ⚙
   ⚙ ✍
   

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9. 5
   From blocking to event-based
   Neutral to latency
   

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10. 6
    Reactive Foundations
    

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11. 7
    Going Reactive
    More for scalability and stability than for speed
    

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12. Reactive Streams
    8
    Publisher Subscriber
    

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13. Reactive Streams
    8
    Publisher Subscriber
    subscribe
    

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14. Reactive Streams
    8
    Publisher Subscriber
    request(n)
    Backpressure
    

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15. Reactive Streams
    8
    Publisher Subscriber
    Backpressure
    onNext(data)
    onNext(data)
    onNext(data)
    

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16. Reactive Streams
    8
    Publisher Subscriber
    Backpressure
    Error|Complete
    

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17. 9
    public interface Publisher {
    void subscribe(Subscriber super T> s);
    }
    public interface Subscriber {
    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 extends Subscriber, Publisher {
    }
    Reactive Streams API
    

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18. 10
    Reactive Streams based libraries:
    

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19. 10
    Reactive Streams based libraries:
    RxJava Reactor Akka Streams
    

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20. 11
    Reactor is a reactive API
    based on reactive streams and Java 8
    

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21. 12
    Flux
    Mono
    

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22. 13
    Flux is a Publisher for 0..n elements
    

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23. 14
    Flux
    Mono
    

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24. 15
    Mono is a Publisher for 0..1 element
    

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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));
    

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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 fetchWeather(String city);
    

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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
    

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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
    

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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
    

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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
    

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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
    

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32. 17
    Building Reactive applications
    

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33. 18
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    interface UserRepository {
    User findOne(String id);
    List findAll();
    void save(User user);
    }
    Blocking API Reactive API
    

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34. 19
    interface UserRepository {
    User findOne(String id);
    List findAll();
    void save(User user);
    }
    Blocking API
    

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35. 19
    interface UserRepository {
    User findOne(String id);
    List findAll();
    void save(User user);
    }
    Blocking API
    Method returns when whole list is received
    

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36. 19
    interface UserRepository {
    User findOne(String id);
    List findAll();
    void save(User user);
    }
    Blocking API
    Throws exception if an error happens
    

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37. 20
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    interface UserRepository {
    User findOne(String id);
    List findAll();
    void save(User user);
    }
    Blocking API Reactive API
    

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38. 21
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    Reactive API
    

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39. 21
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    Reactive API
    Method returns immediately!
    

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40. 21
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    Reactive API
    Elements are received as soon as they are available,
    ending with a success "onComplete" event.
    

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41. 21
    interface ReactiveUserRepository {
    Mono findOne(String id);
    Flux findAll();
    Mono save(Mono user);
    }
    Reactive API
    Mono means error or success,

    no data will be received
    

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42. 22
    Flux:
    Async collection vs. Stream of data
    

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43. 23
    Flux
    

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44. 24
    Flux as a JSON array
    

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45. 24
    GET /users
    …
    200 OK

    Content-Type: application/json
    [
    {"a": "foo", "b": "bar"},
    {"a": "baz", "b": "boo"}
    ]
    Flux as a JSON array
    

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46. 25
    Flux as Server Sent Events
    

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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 as Server Sent Events
    

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48. 26
    Flux as a JSON stream
    

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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 as a JSON stream
    

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50. 27
    Reactive Spring
    

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51. 28
    Spring Framework 5 uses
    Reactor for its reactive foundations
    

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54. 30
    With Reactive Spring, you can use your
    reactive library of choice for your application:
    

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55. 30
    With Reactive Spring, you can use your
    reactive library of choice for your application:
    RxJava Reactor Akka Streams
    

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56. 31
    Reactor
    

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57. 31
    Reactor
    
    
    
    
    

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59. 32
    @Controller, @RequestMapping
    Spring MVC
    Servlet API
    Servlet Container
    

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60. 32
    @Controller, @RequestMapping
    Spring MVC
    Servlet API
    Servlet Container Servlet 3.1, Netty, Undertow
    Spring WebFlux
    HTTP / Reactive Streams
    

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61. 32
    @Controller, @RequestMapping
    Spring MVC
    Servlet API
    Servlet Container
    Router functions
    Servlet 3.1, Netty, Undertow
    Spring WebFlux
    HTTP / Reactive Streams
    

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62. 33
    Flux WebClient
    Streaming API
    

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63. 33
    Flux
    ✔ Reactive API
    ✔ Can consume (infinite) streams
    WebClient
    Streaming API
    

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64. 34
    Flux.zip(tweets, issues)
    WebClient
    Streaming API
    REST API
    WebClient
    

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65. 34
    Flux.zip(tweets, issues)
    ✔ Chain and compose
    WebClient
    Streaming API
    REST API
    WebClient
    

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66. 35
    WebClient
    Web handler
    WebFlux
    

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67. 36
    WebClient
    Web handler
    WebFlux
    

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68. 36
    WebClient
    Web handler
    WebFlux
    ✔ Shared resources (event loop, buffers)
    ✔ Built-in mocking capabilities
    

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69. 37
    WebClient,
    a nice RestTemplate alternative
    

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70. 37
    WebClient,
    a nice RestTemplate alternative
    ✔ Fluent and flexible API
    ✔ Easy configuration
    

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71. 38
    WebFlux demo!
    

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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
    

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73. 40
    WebFlux,
    the functional way
    

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74. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    

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75. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    Mono> route(ServerRequest req)
    

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76. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    boolean test(ServerRequest req)
    

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77. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    Mono handle(ServerRequest req)
    

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78. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    Mono filter(ServerRequest req,

    HandlerFunction next)
    

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79. 41
    ‣ RouterFunction

    ‣ RequestPredicate

    ‣ HandlerFunction

    ‣ HandlerFilterFunction

    

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80. 42
    // Annotation-based Java
    @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE)
    public Flux fetchQuotesStream() { ... }
    

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81. 43
    // Annotation-based Java
    @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE)
    public Flux fetchQuotesStream() { ... }
    route(
    // Functional Java without static imports
    RequestPredicates.
    RequestPredicates.accept(TEXT_EVENT_STREAM)),
    path( )
    { ... }
    )
    .and(
    "/quotes/feed"
    RouterFunctions.
    

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82. 44
    // Annotation-based Java
    @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE)
    public Flux fetchQuotesStream() { ... }
    accept(TEXT_EVENT_STREAM)),
    path( )
    { ... }
    )
    .and(
    "/quotes/feed"
    // Functional Java with static imports
    route(
    

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83. 45
    // Annotation-based Java
    @RequestMapping("/quotes/feed", produces = TEXT_EVENT_STREAM_VALUE)
    public Flux fetchQuotesStream() { ... }
    accept(TEXT_EVENT_STREAM) { ... }
    and
    "/quotes/feed"
    // Functional Kotlin
    router {
    }
    

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84. 46
    @RestController
    public class UserController {
    @GetMapping( )
    public Flux () {
    // ...
    }
    @GetMapping( )
    public Mono (@PathVariable String userId) {
    // ...
    }
    }
    fetchAll
    "/users"
    "/users/{id}"
    fetch
    

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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 {
    ...
    ...
    }
    }
    

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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)
    }
    

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87. 49
    @Bean
    fun dynamicRouter() = router {
    }
    shopRepository.findAll()
    .toIterable()
    .forEach { shop ->
    GET("/${shop.id}") {
    req -> shopHandler.homepage(shop, req)
    }
    }
    

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88. 50
    Spring ❤ Kotlin
    

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90. 52
    inline fun ServerResponse.BodyBuilder.body(publisher: Publisher) =
    body(publisher, T::class.java)
    ServerResponse extensions provided in spring-webflux.jar
    

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91. 52
    inline fun ServerResponse.BodyBuilder.body(publisher: Publisher) =
    body(publisher, T::class.java)
    ServerResponse extensions provided in spring-webflux.jar
    Extend existing Spring Java type
    

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92. 52
    inline fun ServerResponse.BodyBuilder.body(publisher: Publisher) =
    body(publisher, T::class.java)
    ServerResponse extensions provided in spring-webflux.jar
    Extend existing Spring Java type
    Mono findAll(ServerRequest request) {
    return ServerResponse.ok().body(repository.findAll(), User.class);
    }
    Need to specify the type because of type erasure
    

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93. 52
    fun findAll(req: ServerRequest) = ok().body(repository.findAll())
    No need to specify explicitly types thanks

    to Kotlin reified type parameters
    inline fun ServerResponse.BodyBuilder.body(publisher: Publisher) =
    body(publisher, T::class.java)
    ServerResponse extensions provided in spring-webflux.jar
    Extend existing Spring Java type
    

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94. 53
    Kotlin extensions bundled with Spring 5
    

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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
    

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96. 54
    start.spring.io
    

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97. 55
    start.spring.io
    

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98. 56
    Thank You!
    

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