Despite being quite recent, Spring Boot has seen a spectacular start as an amazing kickstarter for Spring-based application. You can now start your project in a matter of minutes, not days! On the other hand, you're still using Java, with all its ceremony regarding code... Wouldn't it be great if we could pair Spring Boot with a powerful yet simple language? In this talk, I'll live code a Spring Boot application using Kotlin, the friendly language provided by JetBrains. Come discover how you can now cut through all the red tape and finally focus only the important stuff.

1. SPRING BOOT AND
KOTLIN, A MATCH
MADE IN HEAVEN
@NICOLAS_FRANKEL

2. ME, MYSELF AND I
@nicolas_frankel #kotlin #springboot
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 By day
• Consultant
 By night
• Developer
• Blogger
• Book author
• Teacher/trainer

3. HYBRIS, AN SAP COMPANY
SAP CUSTOMER EXPERIENCE
@nicolas_frankel #kotlin #springboot
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4. @nicolas_frankel #kotlin #springboot
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5. @nicolas_frankel #kotlin #springboot
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6. WHY SPRING BOOT?
@nicolas_frankel #kotlin #springboot
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Convention over
configuration
• Kickstart a project in minutes,
not days
Out-of-the-box features
• Actuator

7. @nicolas_frankel #kotlin #springboot
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8. KOTLIN
@nicolas_frankel #kotlin #springboot
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Open Source
Compiles to
• JVM bytecode
• JavaScript
• Native (experimental)
A "simpler Scala"
@nicolas_frankel #kotlin #springboot

9. KOTLIN MAIN FEATURES
@nicolas_frankel #kotlin #springboot
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Functional and object-oriented
Statically typed
Null safety
No checked exceptions
Named & optional arguments
Lambdas
Extension properties functions
Java compatibility
(And more...)
@nicolas_frankel #kotlin #springboot

10. THE KILLER FEATURE: EXTENSIONS
@nicolas_frankel #kotlin #springboot
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Extension methods
Extension properties

11. EXTENSION METHOD
@nicolas_frankel #kotlin #springboot
Add new methods on an
existing type
Called like a method on the
type
Translated to static Util
method in the bytecode
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12. KOTLIN MAIN BENEFITS
@nicolas_frankel #kotlin #springboot
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More expressive than Java
Improved OO
Functional too

13. ENOUGH TALK…
@nicolas_frankel #kotlin #springboot
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14. SPRING WEB 5 FUNCTIONAL & KOTLIN
@nicolas_frankel #kotlin #springboot
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https://docs.spring.io/sprin
g/docs/current/spring-
framework-
reference/languages.html#kot
lin-bean-definition-dsl

15. SPRING WEB 5 FUNCTIONAL & KOTLIN
fun routerFunction(userHandler: UserHandler) =
router {
accept(TEXT_HTML).nest {
GET("/") { ok().render("index") }
GET("/sse") { ok().render("sse") }
GET("/users", userHandler::findAllView)
}
"/api".nest {
accept(APPLICATION_JSON).nest {
GET("/users", userHandler::findAll)
}
accept(TEXT_EVENT_STREAM).nest {
GET("/users", userHandler::stream)
}
}
resources("/**", ClassPathResource("static/"))
}
@nicolas_frankel #kotlin #springboot
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16. EXPERIMENTAL: SPRING FU
fun main(args: Array<String>) = application {
bean<UserRepository>()
bean<UserHandler>()
webflux {
server(netty()) {
mustache() codecs {
jackson()
}
routes(import = ::appRoutes)
}
}
}.run(await = true)
fun appRoutes() = routes {
val userHandler = ref<UserHandler>()
GET("/", userHandler::listView)
GET("/api/user", userHandler::listApi)
}
@nicolas_frankel #kotlin #springboot
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17. TAKEWAYS
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Set open for configuration
at compile time
Add no-args constructor for
JPA entities at compile-time
Be careful of WebFlux
The rest is golden!

18. KEY TAKEAWAY
@nicolas_frankel #kotlin #springboot
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19. Q&A
@nicolas_frankel #kotlin #springboot
http://blog.frankel.ch/
@nicolas_frankel
https://git.io/vVSLG
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