Kotlin Backend Development 6 Yrs Recap. The Good, the Bad and the Ugly
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This document is a detailed recap of Kotlin backend development spanning over six years by Haim Yadid, highlighting successes, challenges, and technological evolution. It discusses the growth of community adoption, key tech stack components, and various Kotlin features including data classes, null safety, and coroutines. Additionally, it addresses the migration journey from Java 11 to Java 17 and Kotlin version updates.
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The Promise of Null Safety
val productVersion:String = versions[versionId]
Map<String,Sting>](https://image.slidesharecdn.com/haimyadid-kotlin6yearsrecap-220505064924/85/Kotlin-Backend-Development-6-Yrs-Recap-The-Good-the-Bad-and-the-Ugly-30-320.jpg)
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The Promise of Null Safety
val productVersion:String? = versions[versionId]
Map<String,Sting>](https://image.slidesharecdn.com/haimyadid-kotlin6yearsrecap-220505064924/85/Kotlin-Backend-Development-6-Yrs-Recap-The-Good-the-Bad-and-the-Ugly-31-320.jpg)
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32
The Promise of Null Safety
val productVersion:String = versions[versionId]!!
NullPointerException](https://image.slidesharecdn.com/haimyadid-kotlin6yearsrecap-220505064924/85/Kotlin-Backend-Development-6-Yrs-Recap-The-Good-the-Bad-and-the-Ugly-32-320.jpg)
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The Promise of Null Safety
val productVersion:String = versions[versionId]!!
require(productVersion.status == Staged) {
"Version $versionId: Can't unstage status…" }
versions[versionId] = productVersion.copy(
status = ProductVersionStatus.Draft,
updatedBy = updatedBy)](https://image.slidesharecdn.com/haimyadid-kotlin6yearsrecap-220505064924/85/Kotlin-Backend-Development-6-Yrs-Recap-The-Good-the-Bad-and-the-Ugly-34-320.jpg)
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Extension Functions
fun MutableList<Int>.swap(index1: Int, index2: Int) {
val tmp = this[index1] // 'this' corresponds to the list
this[index1] = this[index2]
this[index2] = tmp
}](https://image.slidesharecdn.com/haimyadid-kotlin6yearsrecap-220505064924/85/Kotlin-Backend-Development-6-Yrs-Recap-The-Good-the-Bad-and-the-Ugly-38-320.jpg)
Kotlin Backend Development 6 Yrs Recap. The Good, the Bad and the Ugly
- 1. Kotlin Backend Development 5 Yrs Recap. The Good, the Bad and the Ugly Haim Yadid VP Technology @ Next Insurance
- 2. Kotlin Backend Development 6 Yrs Recap. The Good, the Bad and the Ugly Haim Yadid VP Technology @ Next Insurance
- 4. NEXT 4
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- 9. NEXT 9
- 10. NEXT #Backend Developers 1 2016 2017 8 150 2022 This is important
- 12. NEXT Kotlin Version 1.0.2 2016 2017 1.1.50 1.6.10 2022
- 14. NEXT 14 ● Working flawlessly in production ● Smooth Onboarding of Java developers ● Good IDE support ● Community Adoption is growing ● Selling point for hiring
- 16. NEXT 16 Some Short stories: Kotlin Promises Are mostly kept
- 17. NEXT Main Tech Stack Components AWS EC2 K8s JVM Kotlin Dropwizard Jetty Jersey Logback JDBI Guice JUNIT Flyway RDS Kotlin Script 17 Jackson
- 18. NEXT Main Tech Stack Components AWS EC2 K8s 18
- 19. NEXT Main Tech Stack Components JUNIT 19
- 20. NEXT Main Tech Stack Components JVM Kotlin 20 AWS EC2 K8s
- 21. NEXT Main Tech Stack Components JVM Kotlin Kotlin Script 21 Policy Rating Formula Rating Formulas Other versions AWS EC2 K8s
- 22. NEXT Main Tech Stack Components Dropwizard Jetty Jersey Logback JDBI Guice 22 Jackson
- 23. NEXT Main Tech Stack Components Flyway RDS 23
- 24. NEXT Main Tech Stack Components AWS EC2 K8s JVM Kotlin Dropwizard Jetty Jersey Logback JDBI Guice JUNIT Flyway RDS Kotlin Script 24 Jackson
- 25. NEXT 25 Data classes - The Prince that was Promised data class AddressInfo( val telephone: String, val street: String, val num: Int, val city: String, val zipCode: String, val state: State? ) ● Widely used >6100 data classes ● Used for DTO, DAO ● Rest API Serialization / deserialization with jackson ● hashcode/equals/(se|ge)tters saves a lot of boilerplate ● copy() helps working with immutable objects
- 26. NEXT 26 Data Classes - Jackson Serialization fun ObjectMapper.applyNiSettings(): ObjectMapper {
- 27. NEXT 27 Data Classes - Jackson Serialization fun ObjectMapper.applyNiSettings(): ObjectMapper { return this .registerModule(KotlinModule())
- 28. NEXT 28 Data Classes - Jackson Serialization fun ObjectMapper.applyNiSettings(): ObjectMapper { return this .registerModule(KotlinModule()) .configure( DeserializationFeature .FAIL_ON_UNKNOWN_PROPERTIES, false)
- 29. NEXT 29 Data Classes - Jackson DeSerialization fun ObjectMapper.applyNiSettings(): ObjectMapper { return this .registerModule(KotlinModule()) .configure( DeserializationFeature .FAIL_ON_UNKNOWN_PROPERTIES, false) .configure( DeserializationFeature.FAIL_ON_NULL_FOR_PRIMITIVES, true) }
- 30. NEXT 30 The Promise of Null Safety val productVersion:String = versions[versionId] Map<String,Sting>
- 31. NEXT 31 The Promise of Null Safety val productVersion:String? = versions[versionId] Map<String,Sting>
- 32. NEXT 32 The Promise of Null Safety val productVersion:String = versions[versionId]!! NullPointerException
- 33. NEXT 33 The Promise of Null Safety val productVersion:String = versions.require(versionId) A better NullPointerException
- 34. NEXT 34 The Promise of Null Safety val productVersion:String = versions[versionId]!! require(productVersion.status == Staged) { "Version $versionId: Can't unstage status…" } versions[versionId] = productVersion.copy( status = ProductVersionStatus.Draft, updatedBy = updatedBy)
- 35. NEXT 35 The Promise of Null Safety ● Null Safety Mechanisms baked in the type system ● No more NPEs ? ● ( not really) >11052 invocations of !! ● Where do they come from ○ interacting with Java based third party libraries ○ Getting values from maps
- 36. NEXT 36 <|*|>
- 37. NEXT 37 Operator Overloading ● 155 overloads (plus,minus,times,get,invoke) ● Most usages makes sense operator fun times(factor: BigDecimal) = … operator fun plus(toAdd: AmountWithAttribution) = … operator fun minus(toSubtract: AmountWithAttribution) = operator fun compareTo(other: AmountWithAttribution) =
- 38. NEXT 38 Extension Functions fun MutableList<Int>.swap(index1: Int, index2: Int) { val tmp = this[index1] // 'this' corresponds to the list this[index1] = this[index2] this[index2] = tmp }
- 39. NEXT 39 Extension Functions private fun String.
- 40. NEXT 40 Extension Functions private fun String.isVersionLowerThan( thatVersion: String) = when { isValidSpecificBranchVersion(thatVersion) && this==thatVersion -> false //same branch isValidSpecificBranchVersion(thatVersion) -> true
- 41. NEXT 41 Extension Functions fun String.isVersionLowerThan( thatVersion: String) = when { isValidSpecificBranchVersion(thatVersion) && this==thatVersion -> false //same branch isValidSpecificBranchVersion(thatVersion) -> true
- 42. NEXT 42 Extension Functions - my preferance private fun isVersionLowerThan( thisVersion:String , thatVersion: String) = …
- 43. NEXT 43 Extension Functions data class WhateverDTO(val state: State, @field:NotBlank val zipCode: String, @field:NotBlank val city: String, @field:NotBlank val streetAddress: String )
- 44. NEXT 44 Extension Functions data class WhateverDTO(val state: State, @field:NotBlank val zipCode: String, @field:NotBlank val city: String, @field:NotBlank val streetAddress: String ) fun WhateverDTO.getAsParamValue() = "${streetAddress}$EOL${city}, ${state.dbName} $zipCode"
- 45. NEXT 45 Our concurrency model & Tx Ctx Jetty Worker Thread CTX Worker Thread CTX Worker Thread CTX Worker Thread CTX Thread Pool(s) Worker Thread CTX Worker Thread CTX Worker Thread CTX Worker Thread CTX Ctx: (MDC) TransactionID Caller Flow OpenID Span
- 46. NEXT 46 Executors - fixing context fun Executor.executeWithContext(r: Runnable) { execute(r) }
- 47. NEXT 47 Executors - MDC Usage fun Executor.executeWithContext(r: Runnable) { val mdcContextInfo = MDCContextInfo.fromMDC() val activeSpan = GlobalTracer.get().activeSpan() val rWithContext = Runnable { mdcContextInfo.populateMDC() GlobalTracer.get().activateSpan(activeSpan) r.run() } execute(rWithContext) }
- 48. NEXT 48 Coroutines : launch fun CoroutineScope.launchWithContext( ): Job = launch( ) also async ,runBlocking, flowOn
- 49. NEXT 49 Coroutines : launch fun CoroutineScope.launchWithContext( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() -> Unit ): Job = launch(MDCContext() + context, start, block) also asyncWithContext,runBlockingWithContext, flowOnWithContext
- 50. NEXT 50 Type Aliases From Kotlin documentation: Type aliases provide alternative names for existing types. If the type name is too long you can introduce a different shorter name and use the new one instead. It's useful to shorten long generic types. For instance, it's often tempting to shrink collection types: typealias NodeSet = Set<Network.Node> typealias FileTable<K> = MutableMap<K, MutableList<File>>
- 51. NEXT 51 Type Aliases - The feature we use too much typealias AffiliateId = Int typealias AgencyId = Int typealias AgencyAggregatorId = Int typealias AgentId = String typealias BundleId = Int typealias BusinessId = String . . . // additional 50 type aliases Controversial in the community as well ○ https://medium.com/@amlcurran/a voiding-primitive-obsession-in-swift -5325b65d521e ○ https://medium.com/@jerzy.chalup ski/kotlin-the-missing-parts-67645d 9a02f4
- 52. NEXT 52 typealias ZipCode = String typealias Address = String fun main() { var zip: ZipCode = "56934" val addr: Address = "bb" zip = addr } Type Aliases - Are not Type Safe
- 53. NEXT 53 abstract class SomeClassResponse( open val success: Success, open val responseMessage: ResponseMessage) Type Aliases - What is behind the magic typealias Success = Boolean typealias ResponseMessage = String
- 54. NEXT 54 abstract class SomeClassResponse( open val success: Boolean, open val responseMessage: String) Type Aliases - What is behind the magic
- 55. NEXT 55 @Deprecated("Stop using me") data class DeprecateMe(val a: String, val b: String) typealias IamNotDeprecatedAndILikeIt = DeprecateMe fun main() { val a = DeprecateMe("a", "b") val c = IamNotDeprecatedAndILikeIt("a", "b") Type Aliases - Hides Deprecation
- 56. NEXT 56 private typealias ValidationResults = List<Pair<OTPValidationResponse, DigitsPasswordData>> Put Type Aliases to Good Use typealias Row = Array<String> typealias StringMatrix = List<Array<String>>
- 57. NEXT 57 @JvmInline value class NiJexlExpression( val expressionString: String) Inline Classes to the rescue ● Prefer inline classes instead of typealias ● Type safety at compilation ● Migration is not so easy. ● There is a problem with inline classes and our current Jackson Version ● Type erased at runtime ….(Heap Dumps ?)
- 58. NEXT 58 A Migration Story Java11 -> Java 17
- 59. NEXT 59 Migrations along the Years ● Migration to Kotlin 1.1.0 ( Java8 support ) was smooth ● Migration to (almost) every version of kotlin immediately ● Migration to Java 11 – only a year ago ) ● Migration to Java 17 – 5 months ago
- 60. NEXT NEXT Build Time Gradle 7.2 Compiler & Bytecode 11 Kotlin Compiler 1.4 libraries 1.5.21 Run Time Kotlin Runtime 1.5.21 JVM 11 / 16 JRE 11 / 16 60 September 2021
- 61. NEXT Proprietary & Confidential NEXT Kotlin - Java Bytecode Compatibility ● Kotlin 1.4.10 supports Java 14 Bytecode (class version) ● Kotlin 1.4.21 supports Java 15 Bytecode (class version) ● Kotlin 1.5.21 supports Java 16 Bytecode (class version) ● By the time java 17 was released 1.7 bytecode was not supported 61 Kotlin
- 62. NEXT NEXT Gradle - Java bytecode Compatibility Gradle https://docs.gradle.org/current/userguide/compatibility.html 62
- 63. NEXT Kotlin API deprecation @Deprecated("Use minOrNull instead." , ReplaceWith("this.minOrNull()")) @DeprecatedSinceKotlin (warningSince = "1.4", errorSince = "1.5", hiddenSince = "1.6") @SinceKotlin("1.1") public fun Iterable<Double>.min(): Double? { return minOrNull() } min() max() minBy() maxBy() minOrNull() maxOrNull() minByOrNull() maxByOrNull() 63
- 64. NEXT Detaching gradle compiler version 64 val kotlinVersion = libs.findVersion("kotlin").get() // 1.6.10 opposed to 1.5.31 from gradle implementation("org.jetbrains.kotlin:kotlin-gradle-plug in:$kotlinVersion") implementation("org.jetbrains.kotlin:kotlin-script-runt ime:$kotlinVersion")
- 66. THANKS.