Poniendo Kotlin en producción a palos

Codemotion 2017 talk https://2017.codemotion.es/agenda.html#5693168230072320/5994131620888576

Transcript

1. Poniendo
   by @andres_viedma
   en producción
   A palos
   MAD · NOV 24-25 · 2017
   

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2. Andrés Viedma
   Andrés Viedma
   @andres_viedma
   @andres_viedma
   

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3. 01 KOTLIN
   

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5. Null safety
   fun printStringLength(maybeString: String?) {
   // maybeString.length would not compile
   if (maybeString != null) {
   // maybeString cannot be null now, it's a String
   println(maybeString.length)
   } else {
   println("")
   }
   }
   ”My billion dollars mistake”
   Tony Hoare
   

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6. fun printStringLength1(maybeString: String?) {
   maybeString?.let { s -> println(s) }
   }
   fun printStringLengthOrEmpty(maybeString: String?) {
   println(maybeString?.length ?: "")
   }
   Null safety
   

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7. A small immutable Kotlin class
   data class TokenInfo(
   val tokenType: String = “auth”,
   val identity: String
   val expiration: Int? = null
   )
   

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8. Constructor with Properties
   class TokenInfo(
   val tokenType: String,
   val identity: String
   (…)
   )
   public final class TokenInfo {
   private final String tokenType;
   private final String identity;
   (…)
   public TokenInfo(
   String tokenType,
   String identity,
   (…)) {
   this.tokenType = tokenType;
   this.identity = identity;
   (…)
   }
   public final String getTokenType() {
   return tokenType;
   }
   public final String getIdentity() {
   return identity;
   }
   }
   

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9. Getters and Setters
   class TokenInfo(
   val tokenType: String,
   val identity: String
   (…)
   )
   public final class TokenInfo {
   private final String tokenType;
   private final String identity;
   (…)
   public TokenInfo(
   String tokenType,
   String identity,
   (…)) {
   this.tokenType = tokenType;
   this.identity = identity;
   (…)
   }
   public final String getTokenType() {
   return tokenType;
   }
   public final String getIdentity() {
   return identity;
   }
   }
   

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10. Named arguments and optional values
    class TokenInfo(
    val tokenType: String = "auth",
    val identity: String,
    val expiration: Int? = null
    )
    val token = TokenInfo(identity = "xxx")
    Immutable classes with
    optional fields?
    Constructors with lots of
    parameters
    Builder object
    

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11. Data classes
    data class TokenInfo(
    val tokenType: String,
    val identity: String
    (…)
    )
    public final class TokenInfo {
    (…)
    public String toString() { (…) }
    public int hashCode() { (…) }
    public boolean equals(Object var1) { (…) }
    public final TokenInfoId copy(String tokenType,
    String identity) {
    (…)
    }
    public final String component1() { (…) }
    public final String component2() { (…) }
    }
    Immutability
    made easier
    

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12. Collections improvements
    List persons = Arrays.asList(
    new Person("Sansa", "Stark"),
    new Person("Jon", "Snow"));
    List personNames = persons.stream()
    .map(p -> p.getName() + " " + p.getSurname())
    .collect(Collectors.toList());
    val persons = listOf(
    Person("Sansa", "Stark"),
    Person("Jon", "Snow"))
    val personNames = persons
    .map { p -> "${p.name} ${p.surname}" }
    Extension functions
    

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13. Collections improvements
    List result = list.stream()
    .flatMap(o -> o.isPresent() ?
    Stream.of(o.get()) : Stream.empty())
    .collect(Collectors.toList());
    val result = list.filter { it != null }
    List result = list.stream()
    .flatMap(o → o.map(Stream::of)
    .orElseGet(Stream::empty))
    .collect(Collectors.toList());
    List result = list.stream()
    .flatMap(Optional::stream)
    .collect(Collectors.toList());
    

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14. String Interpolation
    List persons = Arrays.asList(
    new Person("Sansa", "Stark"),
    new Person("Jon", "Snow"));
    List personNames = persons.stream()
    .map(p -> p.getName() + " " + p.getSurname())
    .collect(Collectors.toList());
    val persons = listOf(
    Person("Sansa", "Stark"),
    Person("Jon", "Snow"))
    val personNames = persons
    .map { p -> "${p.name} ${p.surname}" }
    

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15. Type Inference
    val persons = listOf(
    Person("Sansa", "Stark"),
    Person("Jon", "Snow"))
    val personNames = persons
    .map { p -> "${p.name} ${p.surname}" }
    List persons = Arrays.asList(
    new Person("Sansa", "Stark"),
    new Person("Jon", "Snow"));
    List personNames = persons.stream()
    .map(p -> p.getName() + " " + p.getSurname())
    .collect(Collectors.toList());
    

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16. Gotcha! Now the idea is trapped inside your head
    

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17. Gotcha! Now the idea is trapped inside your head
    

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18. Gotcha! Now the idea is trapped inside your head
    

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19. 02 LET'S DO IT!
    

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20. Tell the team!
    The conformist
    

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21. Tell the team!
    The conformist The idealist
    

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22. Tell the team!
    The conformist The idealist The responsible
    

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23. Tell the team!
    The conformist The idealist The responsible
    AGGG ROOO RAGG
    AGGG ROOO RAGG
    ROOOOOOOGHH!
    ROOOOOOOGHH!
    

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24. What about the rest of the company?
    

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25. Option 1...
    

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26. Option 2: Talk to them
    

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27. ●
    Can affect development time
    ●
    Misunderstandings can increase bug rate
    ●
    Service responsibility is not fixed
    Not just YOUR team
    Learning cost
    

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28. ●
    Learning curve very smooth
    ●
    On doubt, use Java style and methods
    ●
    Not a real paradigm change
    ●
    Same libraries and concepts
    Learning cost ® BUT...
    

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29. ●
    Good documentation
    ●
    Short library
    ●
    Is there a general interest in Kotlin in the company?
    Kotlin community
    Android devs pushing for a change
    Learning cost ® BUT... (2)
    

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30. ●
    It's production!
    ●
    New technology, may have bugs
    ●
    Adds code “behind the courtains”
    ●
    Any weird behaviour affecting memory, garbage collection...
    Can affect Performance
    

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31. ●
    Same Java VM
    ●
    You can see compiled bytecode
    ●
    Decompile problematic code to Java and tune it
    ●
    Start a component in Java and then convert it to Kotlin
    Can affect Performance ® BUT...
    

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32. ●
    Extension functions are just a trick, no overhead
    ●
    Null checks are a small runtime overhead
    ●
    Platform and base libraries are the sane
    ●
    Kotlin library overhead not important for backend
    Can affect Performance ® BUT... (2)
    

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33. ●
    Increased build time
    ●
    Find equivalent tools
    ●
    Adaptation to those tools
    Tooling problems
    

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34. ●
    Same IDE: IntelliJ, Eclipse...
    ●
    Same build tools: Maven, Gradle...
    ●
    In a microservices architecture build time not so critical
    Seconds?
    Tooling problems ® BUT...
    

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35. ●
    What if Kotlin stops being “cool”?
    ●
    What if nobody uses it anymore?
    ●
    What if it just dissapears?
    Supported / created by Jetbrains
    Long-term vision
    

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36. Long-term vision ® BUT...
    

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37. 03 10 MONTHS
    LATER...
    

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38. ●
    Development time basically the same
    ●
    Code Reviews more interesting!
    ●
    Our Java platform was 100% compatible
    Learning cost?
    

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39. ●
    Rest of the company?
    4 teams doing services in Kotlin
    Kotlin now official in the company for Android
    Learning cost?
    

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40. final vs. open
    Some Java libraries rely on
    dinamically creating subclasses
    ●
    Interceptors and other injection “black magic”
    Spring, Guice…
    ●
    Mocks: Mockito, Spock
    

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41. Compiler plugins
    ●
    All-open: Make classes open
    Shortcut: Spring
    ●
    No-args: Create a no-args constructor
    Shortcut: JPA
    Beware!: only by annotations
    

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42. Compiler plugins ® All-open not enough
    ●
    @Transactional problem (if no class annotation)
    Explicit open class and methods
    ●
    Mocks?
    Mockito 2.1.0 “inline mocks”: “incubating”
    Kotlin-runner library: explicit packages
    

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43. Compiler plugins ® No-args not enough
    ●
    Object Mapper libraries
    Explicit no-args constructor
    ●
    Spock tests
    Named parameters don’t work from Java / Groovy
    

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44. const val ONE = 1 // MyObject(1) NO OBJECTS ALLOWED
    // Translated to: public static final
    class Constants {
    companion object {
    const val TWO = 2 // MyObject(2) NO OBJECTS ALLOWED
    // Translated to: inlined
    val THREE = MyObject(3) // Translated to private static
    // + Companion class with getter
    @JvmField val FOUR = MyObject(4) // Translated to public static final
    }
    }
    Constants: too many options?
    https://blog.egorand.me/where-do-i-put-my-constants-in-kotlin/
    

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45. val description: String (type after identifier)
    

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46. val description: String (type after identifier)
    

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47. Can affect Performance?
    

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48. ●
    Eclipse with Kotlin and Groovy tests just don’t work
    ●
    Eclipse incremental compilation a bit slow
    ●
    Some crashes when updating IntelliJ plugin
    ●
    Incremental build disabled by default in some versions
    Maven+Gradle
    ●
    Checkstyle, Findbugs…
    Tooling problems?
    

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49. ●
    Eclipse with Kotlin and Groovy tests just don’t work
    ●
    Eclipse incremental compilation a bit slow
    ●
    Some crashes when updating IntelliJ plugin
    ●
    Incremental build disabled by default in some versions
    Maven+Gradle
    ●
    Checkstyle, Findbugs…
    Tooling problems?
    

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50. 04 Beyond
    the basics
    

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51. Functional features
    fun processPersonName(person: Person?, processor: (String) -> Boolean) =
    processor(
    when(person) {
    null -> "null"
    is AnonymousPerson -> "anonymous"
    else -> when {
    person.isBoss -> "a boss"
    else -> "the simple ${person.name}"
    }
    }
    )
    

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52. ●
    Not 100% functional
    ●
    Higher kind types
    ●
    Typeclasses
    ●
    Proposal (KEEP) in discussion to add them, by @raulraja
    ●
    Kategory library - http://kategory.io/
    Functional paradigm?
    

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53. Black magic
    companion { [constants: USER_ID, PRODUCTS, OK_RESULT...) }
    val storeCatalogStub = Stub {
    getProductsForUserId(USER_ID) <= PRODUCTS
    }
    val storeMock = Mock()
    val purchaseHistoryMock: PurchaseHistory = Mock()
    fun `Purchase correct product available in the store`() {
    given("A valid user") {
    userService.isValidUser(USER_ID) <= true
    } `when`("The user tries to do the purchase") {
    purchaseOperation.perform(USER_ID, PRODUCT_ID)
    } then("Product is purchased") {
    1 * storeMock.purchaseProduct(USER_ID, PRODUCT_ID, null.not()) <= OK_RESULT
    } and("Operation is logged") {
    (1..any) * purchaseHistoryMock.logProductPurchased(USER_ID, PRODUCT_ID, any())
    } and("No more interactions") {
    0 * any
    }
    }
    

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54. Black magic
    companion { [constants: USER_ID, PRODUCTS, OK_RESULT...) }
    val storeCatalogStub = Stub {
    getProductsForUserId(USER_ID) <= PRODUCTS
    }
    val storeMock = Mock()
    val purchaseHistoryMock: PurchaseHistory = Mock()
    fun `Purchase correct product available in the store`() {
    given("A valid user") {
    userService.isValidUser(USER_ID) <= true
    } `when`("The user tries to do the purchase") {
    purchaseOperation.perform(USER_ID, PRODUCT_ID)
    } then("Product is purchased") {
    1 * storeMock.purchaseProduct(USER_ID, PRODUCT_ID, null.not()) <= OK_RESULT
    } and("Operation is logged") {
    (1..any) * purchaseHistoryMock.logProductPurchased(USER_ID, PRODUCT_ID, any())
    } and("No more interactions") {
    0 * any
    }
    }
    Lambda param after
    parenthesis
    Code generation
    (compiler plugin)
    

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55. Black magic
    companion { [constants: USER_ID, PRODUCTS, OK_RESULT...) }
    val storeCatalogStub = Stub {
    getProductsForUserId(USER_ID) <= PRODUCTS
    }
    val storeMock = Mock()
    val purchaseHistoryMock: PurchaseHistory = Mock()
    fun `Purchase correct product available in the store`() {
    given("A valid user") {
    userService.isValidUser(USER_ID) <= true
    } `when`("The user tries to do the purchase") {
    purchaseOperation.perform(USER_ID, PRODUCT_ID)
    } then("Product is purchased") {
    1 * storeMock.purchaseProduct(USER_ID, PRODUCT_ID, null.not()) <= OK_RESULT
    } and("Operation is logged") {
    (1..any) * purchaseHistoryMock.logProductPurchased(USER_ID, PRODUCT_ID, any())
    } and("No more interactions") {
    0 * any
    }
    }
    Operator overloading
    Reified generics
    Extension functions
    https://github.com/Koxalen
    

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56. More...
    ●
    Coroutines
    ●
    Type aliases
    ●
    Sealed classes
    ●
    Delegated properties
    ●
    Inline functions
    

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57. Android
    ●
    Anko library
    ●
    Consider performance and limits
    7k methods (65k methods limit): 10%
    380 KB
    Compilation slower
    

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58. Multi-platform
    ●
    Javascript
    Kotlin wrapper for ReactJS
    ●
    Native
    Kotlin plugin for CLion
    Kotlin/Native iOS support
    Not only the JVM!
    KotlinConf app fully made with Kotlin
    

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59. SO WHAT???
    05
    

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60. Yay or Nay?
    ●
    Controlled risk, but… worth it?
    ●
    What’s the benefit?
    Mostly syntatic sugar
    Productivity really improved???
    

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61. Yay or Nay?
    ●
    Controlled risk, but… worth it?
    ●
    What’s the benefit?
    Mostly syntatic sugar
    Productivity really improved???
    How about thinking about PEOPLE
    instead of PRODUCTS?
    

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62. It’s all about LEARNING
    and MOTIVATION
    

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64. Questions?
    Andrés Viedma · @andres_viedma
    

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