Kotlin on the Cloud

Transcript

1. Kotlin on the Cloud João Carvalho - GDG Lisboa -

   Oct 12 2017

2. About me

3. About me • Senior Developer / Team Lead @ Talkdesk

   • Backend Developer • IST Alumni (Student & Developer) • PT.JUG Speaker • Follow me on Twitter @johnkarva

4. Cloud Native Apps https://pivotal.io/cloud-native

5. “Cloud-native is an approach to building and running applications that

   fully exploits the advantages of the cloud computing delivery model. Cloud-native is about how applications are created and deployed, not where.”

6. • Devops • Continuous Delivery • Microservices • Containerization

7. Predictability

8. 12 Factor App 1. Single codebase, multiple deploys 2. Explicit

   Dependencies 3. Store Config in Environment 4. Backing Services as resources 5. Separate Build, Release, Execution 6. Standalone (Volatile) Process 7. Port Binding 8. Multiple Process Types 9. Disposability 10. Environment Parity 11. Logs as Event Streams 12. One-off Admin Tasks

9. OS-Agnostic

10. Auto-Scaling

11. Independence

12. Quick Recovery

13. Agility

14. Kotlin

15. Why not Java 8/9?

16. Null Safety

17. public void printName(Person person) { System.out.println(person.getName()); }

18. public void printName(Person person) { System.out.println(person.getName()); } null

19. None

20. fun printName(person: Person) { println(person.name) }

21. printName(null) ERROR: Null cannot be a value of non-null type

    Person.

22. fun printName(person: Person?) { if (person != null) { println(person.name)

    } }

23. Safe Navigation

24. private String safeGetName(Person person) { return person == null ?

    null : person.getName(); }

25. fun safeGetName(person: Person?): String? { return person?.name }

26. fun safeGetName(person: Person?): String { return person?.name ?: "Unknown" }

27. Properties

28. class Person(name: String) { private val name: String init {

    this.name = name } }

29. class Person(private val name: String)

30. Delegated Properties

31. val lazyValue: String by lazy { println("computed!") "Hello" }

32. Extension Functions

33. fun String.helloize() = "Hello $this" "World".helloize()

34. Data Classes

35. public class Person { private String name; private int age;

    public Person(String name, int age) { this.name = name; this.age = age; } (...) }

36. public String getName() { return name; } public void setName(String

    name) { this.name = name; } @Override public boolean equals(Object o) { (Stuff generated by your IDE) } @Override public int hashCode() { int result = name.hashCode(); result = 31 * result + age; return result; }
37. None

38. data class Person(var name: String, var age: Int)

39. data class Person(val name: String, val age: Int)

40. val john = Person("John", 21) val olderJohn = john.copy(age =

    78)

41. And much more... • No Semicolons! • Lambda Expressions and

    Inline Functions • Type inference • Named Arguments • Default Values • String Interpolation • Ranges • Immutable Collections (Kind of) • Collection helpers • Infix Functions • DSL Support

42. Performance

43. Tooling

44. Getting Started

45. None
46. None
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48. None

49. @RestController @SpringBootApplication public class DemoApplication { public static void main(String[]

    args) { SpringApplication.run(DemoApplication.class, args); } @GetMapping("/hello") public String hello() { return "Hello World!"; } }

50. http://shop.oreilly.com/product/0636920038252.do

51. Cloud-Native Kotlin?

52. None

53. https://docs.spring.io/spring/docs/current/spring-framework-reference/kotlin.html

54. Demo Time!

55. Questions?