Accompanying slides for the hands-on session. All code at https://github.com/jaju/fnconf-2019-jvm-interop

1. JVM Interop acrossJVM Interop across
LanguagesLanguages
Ravindra R. Jaju, TamizhvendanRavindra R. Jaju, Tamizhvendan
@jaju, @tamizhvendan@jaju, @tamizhvendan

2. The JVMThe JVM
A beautiful beast
Beautiful, because, versatile
Beast, because, performance
Evolution has been consistent

3. The JVMThe JVM
A beautiful beast
Beautiful, because, versatile
Beast, because, performance
Evolution has been consistent
And of late, faster

4. The FoundationsThe Foundations
Basic Types
Basic Collection Types
Not the least - the JVM Specs

5. Basic TypesBasic Types
They are part of the JVM Specs
All implementations use them
Allows for direct interoperability

6. Basic Collection TypesBasic Collection Types
Available as Interfaces
Not part of the JVM Specs
But leave design choices open

7. ImplementationsImplementations
Languages are free to choose
Syntax
Parser implementation
Compiler implementation

8. Some LanguagesSome Languages
JRuby
Scala
Clojure
Kotlin
Groovy

9. ClojureClojure
Basic Types are Java Types
; user=> (class 1)
java.lang.Long
; user=> (class "abc")
java.lang.String
; user=> (class true)
java.lang.Boolean

10. ClojureClojure
Collection types are Java Types
#{} -> java.util.Set
'() -> java.util.List
[] -> java.util.List, java.util.RandomAccess
{} -> java.util.Map

11. KotlinKotlin
package kotlin.collections
public actual typealias HashSet<E> =
java.util.HashSet<E>
public actual typealias HashMap<K, V> =
java.util.HashMap<K, V>
/* And more */

12. ScalaScala
A different story, but…

13. ScalaScala
A different story, but…
You have in-built converters

14. The PhilosophyThe Philosophy
Play to language's strength
Keep crossover data simple
When in doubt, go for the LCD

15. The PhilosophyThe Philosophy
Play to language's strength
Keep crossover data simple
When in doubt, go for the LCD
Least Common Denominator

16. Code TimeCode Time
A simple web-app
Single process, mutiple languages
Java
Clojure
Scala
Kotlin

17. Code Time (contd)Code Time (contd)
Cross-language ow
Leveraging strengths

18. Hello WorldHello World
Endpoints
/hello/{language}/{name}

19. AlbumsAlbums

20. JavaJava
Endpoint /albums/v1
GET, POST with JSON

21. Java + Clojure + ScalaJava + Clojure + Scala
Endpoint /albums/v2
GET, POST with JSON
Extra input processing

22. Java + Clojure + ScalaJava + Clojure + Scala
Endpoint /albums/v2
GET, POST with JSON
Extra input processing
The Clojure Dev Work ow!

23. Java + Kotlin + ClojureJava + Kotlin + Clojure

24. Java + Kotlin + ClojureJava + Kotlin + Clojure
The Clojure Dev Work ow!

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