Reactive programming is a new concept that is catching everyone’s eyes these days. The concept has been adopted by the various aspects of software engineering be it application development or DevOps. Our software development languages are also not untouched from it. So, how can JAVA which has such a large community refrain itself from going reactive? The foundational topics for this talk will revolve around the ideas of reactive programming and what steps JAVA has taken towards being reactive. This would involve the latest buzz words in the market: Reactive streams, Reactive stream specification, the concept of mono and flux. We will also be touching how spring has used these features of reactive streams to make a new API development framework: Spring Boot Webflux. We hope the talk will help to understand Reactive programming aspects of JAVA and it will not bewilder the users as now they know that it’s a coding style that centres on the effective management of changes with async data streams.

1. Let’s go reactive with
JAVA Presented By :
Vinisha Sharma
Software consultant - Knoldus Inc

2. © 2018 Minimal – Presentation template
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Agenda
● Reactive Programming
● Reactive Streams
Specification
● Project Reactor
● Mono/ Flux
● Spring Boot Webflux
● Demo

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❑ Programming paradigm oriented around - data flows and
propagation of change.
❑ Asynchronous and Non Blocking.
❑ Data flow as an Event/Message Driven stream
Reactive Programming

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Reactive Manifesto

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Reactive
Streams

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Reactive streams
Reactive Streams is an initiative to provide a standard for asynchronous
stream processing with non-blocking back pressure
Functional Style Code
● Java 8 Streams API
● Lambdas
Event Driven Streams
● Event or Message for
every result item
from Data Source
● Event or Message for
Completion or error
● Asynchronous and
non-blocking
Deferred Push/Pull
Model
Back Pressure
F
BE
D

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Imperative Programming

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Reactive Streams
Specification

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Reactive Stream Specification
Specification or Rules for a Reactive Stream
(Created by Pivotal, Netflix, LightBend, Twitter
etc...)

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public interface Publisher<T> {
public void subscribe(Subscriber<? super T>
s);
}
❑ Represents the Data source
❑ Database
❑ External Service, etc…..
Publisher

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public interface Subscriber<T> {
public void onSubscribe(Subscription s);
public void onNext(T t);
public void onError(Throwable t);
public void onComplete();
}
❑ Represents the consumer of the stream data
Subscriber

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public interface Subscription {
public void request(long n);
public void cancel();
}
Subscription

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public interface Processor<T, R> extends
Subscriber<T>, Publisher<R> {
}
❑ A Processor represents a processing stage—which is both
a Subscriber and a Publisher.
Processor

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Publisher/Subscriber Event Flow

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Publisher/Subscriber Event Flow

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Data Flow as an Event Driven Stream

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Data Flow as an Event Driven Stream
❏ On Error

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Data Flow as an Event Driven Stream
❏ No data

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Back pressure

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Project Reactor
and
Spring Webflux

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❑ Reactor is a fully non-blocking reactive programming foundation for
the JVM, with efficient demand management (in the form of managing
"backpressure").
❑ Integrates directly with the Java 8 functional APIs, notably
CompletableFuture, Stream, and Duration.
❑ Reactive Types - Offers asynchronous sequence (MONO/FLUX) for
reactive streams
Project Reactor
<dependency>
<groupId>io.projectreactor</groupId>
<artifactId>reactor-core</artifactId>
</dependency>

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❑ Publisher<T> that emits at most one item
❑ Optionally terminates with an onComplete signal or an onError signal.
Mono

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❑ Publisher<T> that emits 0 to n items
❑ Optionally terminates with an onComplete signal or an onError signal.
Flux

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Mono Vs Flux
Mono<Student> Flux<Student>

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❑ Reactive-stack web framework
❑ Non Blocking and Supports Reactive Streams back
pressure
❑ Runs on such servers as Netty, Undertow, and Servlet 3.1+
containers.
Spring Webflux

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DEMO

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❑ https://projectreactor.io/
❑ https://github.com/reactive-streams/reactive-streams-jvm
❑ https://stackify.com/reactive-spring-5/
References

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Thank You

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Stay in touch
Contact Details:
vinsha.sharma@knoldus.com
or
linkedin.com/in/vinisha-sharma-26538a135