Kotlin on the Cloud

Transcript

1. 1.

   Kotlin on the Cloud João Carvalho - GDG Lisboa -

   Oct 12 2017
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   About me

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   About me • Senior Developer / Team Lead @ Talkdesk

   • Backend Developer • IST Alumni (Student & Developer) • PT.JUG Speaker • Follow me on Twitter @johnkarva
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   Cloud Native Apps https://pivotal.io/cloud-native

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   “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.”
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   • Devops • Continuous Delivery • Microservices • Containerization

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   Predictability

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   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
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   OS-Agnostic

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    Auto-Scaling

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    Independence

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    Quick Recovery

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    Agility

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    Kotlin

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    Why not Java 8/9?

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    Null Safety

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

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

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    None
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    fun printName(person: Person) { println(person.name) }

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

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

    } }
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    Safe Navigation

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

    null : person.getName(); }
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    fun safeGetName(person: Person?): String? { return person?.name }

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

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    Properties

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

    this.name = name } }
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    class Person(private val name: String)

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    Delegated Properties

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

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    Extension Functions

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

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    Data Classes

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

    public Person(String name, int age) { this.name = name; this.age = age; } (...) }
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    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; }
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    None
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    data class Person(var name: String, var age: Int)

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

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

    78)
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    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
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    Performance

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    Tooling

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    Getting Started

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    None
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    None
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    None
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    None
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    @RestController @SpringBootApplication public class DemoApplication { public static void main(String[]

    args) { SpringApplication.run(DemoApplication.class, args); } @GetMapping("/hello") public String hello() { return "Hello World!"; } }
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    http://shop.oreilly.com/product/0636920038252.do

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    Cloud-Native Kotlin?

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    None
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    https://docs.spring.io/spring/docs/current/spring-framework-reference/kotlin.html

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    Demo Time!

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    Questions?