Today almost every product has an API, to integrate in other products or to made the data available to the outside world. Most API’s are using traditional patterns and technology. With the rise of Angular, React and other modern frameworks there is a need for non blocking API’s. Meet Reactive streams, like Spring Webflux, to super charge your API. In this session I will tell about and show you Reactive API’s and more

1. Super charge your API’s with Reactive streams
Frank van der Linden
Full stack Developer
elstar IT

2. About me
• Freelance Full stack Java developer
• Owner of elstar IT
• Curious of new technology
• IBM Champion 2013, 2014, 2017, 2018 and 2019

3. How to proceed
• Introduction of Reactive programming
• Spring Boot and Webflux
• Build your first reactive API
• Demo and coding

4. Introduction of Reactive
programming

5. Reactive programming is programming with asynchronous data streams.

6. Blocking API calls

7. Blocking API calls
• Limited amount of requests
• Could cause wait time
• Useful for request dependencies

8. Non-Blocking API calls

9. Non-Blocking API calls
• (Almost) no limited requests
• Can process multiple requests
• Not knowing when response are returned
• Modern javascript frameworks rely on. (Angular, React, VueJS)

10. Reactive manifesto

11. Reactive manifesto
• Responsive: a reactive system needs to handle requests in a
reasonable time
• Resilient: a reactive system must stay responsive in the face of
failures
• Elastic: a reactive system must stay responsive under various
loads
• Message driven: components from reactive systems interacts
using asynchronous message passing

12. Publish/Subscribe principle
• Loose coupling
• Scalability
• Non-blocking
• 4 interfaces
• event bus: Apache Kafka or IBM MQ

13. Reactive frameworks
• Node.js
• RxJava
• RxJS - standard used by the major frontend frameworks
• Spring Webflux
• Lightbend (Akka)
• Vert.x

14. Spring Boot and Webflux

15. First things first

16. Spring boot
• Open Source, coordinated by Pivotal
• Java based applications
• Auto configure as much as possible
• Built in metrics and health checks
• Very good documentation

17. Spring boot - component scan
• @Service, @Controller, @Repository and more @Components will be
scanned
• @Autowired will glue everything together

18. Spring boot - runs everywhere
• Embedded Tomcat makes it just run
• Runs on Docker
• Runs on Cloud Foundry, like IBM and PCF
• Tomcat can excluded, then it runs on Websphere, Tomcat or WildFly
• Even on Domino, http://hasselba.ch/blog/?p=2589

19. Spring Webflux

20. Spring Webflux
• Part of the Spring Framework
• Available since Spring 5.0
• Uses Netty as webserver instead of Tomcat
• Uses the Reactor project under the hood

21. Spring Webflux - important objects
• Mono, returns 0 or 1 object
• Flux, returns 0 or N objects
• WebClient, reactive version of RestTemplate

22. Spring Webflux - Mono example

23. Spring Webflux - Flux example

24. Spring Webflux - WebClient example

25. Build your first reactive API

26. Start your first reactive API
• Install Maven or Gradle
• Move to start.spring.io
• Fill in all the fields and select the dependencies
• Generate, download and open project in IDE
• Run ‘mvn clean install’ for all the dependencies
• Start coding
• Run application via ‘mvn spring-boot:run’

27. Spring Initializr

28. Project structure
• application.yaml => properties
• pom.xml => dependencies

29. Application properties
• port: on which the service is available
• profiles: dev or prod
• can used in Java classes
• can also moved outside the application

30. Repository
• Connect to MongoDb
• Auto config via property
• spring.data.mongodb.uri

31. Controller
• GET
• POST
• DELETE
• PATCH

32. Service
• Uses WebClient
• Connect to other API’s

33. Secure the API

34. Swagger the API

35. Router
• NEW RouterFunction
• Can replace the Controller
• Uses a Handler class to get the data (Common scenario)

36. Demo Application

38. Demo application
• Spring boot
• Spring Webflux
• Spring Security
• MongoDb
• Angular 8 (just upgraded)

39. Reactive Streams Starter
https://github.com/flinden68/reactive-streams-starter

40. Questions
Asynchronous coordinated lifecycles
Chai Stofkoper

41. Reach out to me
@flinden68
https://www.elstarit.nl
flinden68@elstarit.nl
https://nl.linkedin.com/in/flinden68
https://github.com/flinden68

42. Resources
• Spring Initializr
• http://start.spring.io/
• Spring Webflux
• https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html
• Spring Boot
• https://projects.spring.io/spring-boot/

43. Resources
• Maven
• https://maven.apache.org/
• Gradle
• https://gradle.org/
• Reactive Streams Starter
• https://github.com/flinden68/reactive-streams-starter