JavaZone 2022 - Building Kotlin DSL.pdf
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The document discusses Kotlin DSL and provides examples of using Kotlin as a domain specific language. It demonstrates how to build type-safe builders using Kotlin, including defining DSL blocks, extension functions and properties, infix notation, lambda receivers, and context receivers to define internal and external DSLs. Code samples are provided of building clients and dates using DSL syntax and context requirements.
JavaZone 2022 - Building Kotlin DSL.pdf
- 3. Why Kotlin?
- 10. tailored for a speci fi c task “Domain-speci fi c”, i.e.
- 11. External
- 17. Internal
- 20. +
- 25. They all look similar!
- 26. foo { bar { baz = "Hello!" qux = quux { corge = "Blah" } } }
- 27. foo { bar { baz = "Hello!" qux = quux { corge = "Blah" } } }
- 28. foo { bar { baz = "Hello!" qux = quux { corge = "Blah" } } }
- 29. foo { bar { baz = "Hello!" qux = quux { corge = "Blah" } } }
- 30. foo { bar(grault = 1) { baz = "Hello!" qux = quux { corge = "Blah" } } }
- 31. foo { bar(grault = 1) { baz = "Hello!" qux = quux { corge = Blah() } } }
- 32. foo { bar(grault = 1) { baz = "Hello!" qux = quux { corge = Blah() } } }
- 33. Let’s write some code! https://github.com/antonarhipov/kotlin-dsl-examples
- 34. Let’s write some code! https://github.com/antonarhipov/kotlin-dsl-examples
- 36. final ClientBuilder builder = new ClientBuilder(); builder.setFirstName("Anton"); builder.setLastName("Arhipov"); final TwitterBuilder twitterBuilder = new TwitterBuilder(); twitterBuilder.setHandle("@antonarhipov"); builder.setTwitter(twitterBuilder.build()); final CompanyBuilder companyBuilder = new CompanyBuilder(); companyBuilder.setName("JetBrains"); companyBuilder.setCity("Tallinn"); builder.setCompany(companyBuilder.build()); final Client client = builder.build(); System.out.println("Created client is: " + client); val client = createClient { firstName = "Anton" lastName = "Arhipov" twitter { handle = "@antonarhipov" } company { name = "JetBrains" city = "Tallinn" } } println("Created client is: " + client.consoleString)
- 37. //extension property val Client.consoleString: String get() = "${twitter.handle} ${company.name}" //extension method fun Client.toConsoleString(): String { return "${twitter.handle} ${company.name}" }
- 38. fun createClient(c: ClientBuilder.() -> Unit): Client { val builder = ClientBuilder() c(builder) return builder.build() } fun ClientBuilder.company(t: CompanyBuilder.() -> Unit) { company = CompanyBuilder().apply(t).build() } fun ClientBuilder.twitter(t: CompanyBuilder.() -> Unit) { twitter = TwitterBuilder().apply(t).build() } Lambda with receiver Extension methods
- 40. dateTime = LocalDateTime.of(2018, Month.DECEMBER, 11, 0, 0) dateTime = 11 December 2018 at (14 hh 0) infix fun Int.December(n: Int) : LocalDate { return LocalDate.of(n, Month.DECEMBER, this) } infix fun LocalDate.at(n: Pair<Int, Int>): LocalDateTime { return this.atTime(n.first, n.second) } infix fun Int.hh(n: Int): Pair<Int, Int> { return Pair(this, n) }
- 42. context(DateContext) @DateDsl infix fun Int.March(n: Int): LD = LD.of(n, Month.MARCH, this) class DateContext val client = createClient { / / . . . dob = 24 March 2000 } 24 March 2000 fun client(block: context(DateContext) ClientBuilder.() - > Unit): Client { val builder = ClientBuilder() with(DateContext()) { block(builder) } return builder.build() } Context object Context requirement Context requirement Context scope The function is available in the context scope The function is not available, missing DateContext
- 43. T.() -> Unit
- 44. Kotlin { YouTube = "youtube.com/kotlin" Slack = "slack.kotl.in" } me { name = "Anton Arhipov" twitter = "@antonarhipov" slides = speakerdeck.com/antonarhipov } books { courses {