Kotlin on the Cloud

Slides for my 'Kotlin on the Cloud' talk at the Google Developer Group Lisboa's Kotlin Night.

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
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; }
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
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?
53. https://docs.spring.io/spring/docs/current/spring-framework-reference/kotlin.html
54. Demo Time!
55. Questions?