Kotlin_for_server-side_application_development.pdf

Transcript

1. @antonarhipov Kotlin for server-side application development
2. @antonarhipov
4. 2011 - alternative JVM language
5. 2011 - alternative JVM language Then - Android, JavaScript, LLVM, WASM…..
6. 2011 - alternative JVM language Then - Android, JavaScript, LLVM, WASM….. 2017 - O ffi cially supported for Android
7. 2011 - alternative JVM language Multi-Platform Projects Then - Android, JavaScript, LLVM, WASM….. 2017 - O ffi cially supported for Android
8. What developers say about
9. What developers say about Concise & modern
10. What developers say about Concise & modern Null-safe
11. What developers say about Concise & modern MPP, Kotlin/JS Null-safe
12. What developers say about Concise & modern Coroutines! MPP, Kotlin/JS Null-safe
13. What developers say about Concise & modern Coroutines! MPP, Kotlin/JS stdlib Null-safe
14. Just use it once…
15. Who uses Kotlin? for server-side application development
19. Code sharing across clients
20. Code sharing between frontend and backend
23. https://youtu.be/4GkoB4hZUnw
26. From monolith to microservices From Java to Kotlin Developer happiness
27. https://youtu.be/7YJyPXjLdug
28. https://youtu.be/7YJyPXjLdug In Kotlin, you can build a data model that’s going to match exactly how your GraphQL schema looks like
30. Adobe: leveraging Kotlin Coroutines https://medium.com/adobetech/ streamlining-server-side-app- development-with-kotlin-be8cf9d8b61a
31. Adobe: leveraging Kotlin Coroutines https://medium.com/adobetech/ streamlining-server-side-app- development-with-kotlin-be8cf9d8b61a
33. Extreme code reuse with Kotlin Multiplatform
34. Extreme code reuse with Kotlin Multiplatform Brave new world with microservices and happier developers!
35. Extreme code reuse with Kotlin Multiplatform Brave new world with microservices and happier developers! Expressiveness and safety for building GraphQL APIs (with Java interoperability!)
36. Extreme code reuse with Kotlin Multiplatform Brave new world with microservices and happier developers! Expressiveness and safety for building GraphQL APIs (with Java interoperability!) High-load, lock-free software with Kotlin Coroutines
40. What framework(s) should I use? Libraries, build tools, etc?
41. Hexagon KVision
42. Spring with Kotlin
46. import org.springframework.boot.autoconfigure.SpringBootApplication import org.springframework.boot.runApplication … @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) }
47. import org.springframework.boot.autoconfigure.SpringBootApplication import org.springframework.boot.runApplication … @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) }
48. import org.springframework.boot.autoconfigure.SpringBootApplication import org.springframework.boot.runApplication … @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) }
49. import org.springframework.boot.autoconfigure.SpringBootApplication import org.springframework.boot.runApplication … @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) } @RestController class MessageResource(val service: MessageService) { @GetMapping fun index(): List<Message> = service.findMessages() @PostMapping fun post(@RequestBody message: Message) { service.post(message) } }
50. @Service class MessageService(val db: MessageRepository) { fun findMessages(): List<Message> = db.findMessages() fun post(message: Message){ db.save(message) } } interface MessageRepository : CrudRepository<Message, String>{ @Query("select * from messages") fun findMessages(): List<Message> } @Table("MESSAGES") data class Message(@Id val id: String?, val text: String)
51. @Service class MessageService(val db: MessageRepository) { fun findMessages(): List<Message> = db.findMessages() fun post(message: Message){ db.save(message) } } interface MessageRepository : CrudRepository<Message, String> { @Query("select * from messages") fun findMessages(): List<Message> } @Table("MESSAGES") data class Message(@Id val id: String?, val text: String)
52. @Service class MessageService(val db: MessageRepository) { fun findMessages(): List<Message> = db.findMessages() fun post(message: Message){ db.save(message) } } interface MessageRepository : CrudRepository<Message, String>{ @Query("select * from messages") fun findMessages(): List<Message> } @Table("MESSAGES") data class Message(@Id val id: String?, val text: String)
53. @Service class MessageService(val db: MessageRepository) { fun findMessages(): List<Message> = db.findMessages() fun post(message: Message){ db.save(message) } } interface MessageRepository : CrudRepository<Message, String>{ @Query("select * from messages") fun findMessages(): List<Message> } @Table("MESSAGES") data class Message(@Id val id: String?, val text: String) Not to be used with JPA!
56. https://stackover fl ow.com/questions/58127353/should-i-use-kotlin-data-class-as-jpa-entity Resources: https://kotlinexpertise.com/hibernate-with-kotlin-spring-boot/ https://dzone.com/articles/kotlin-data-classes-and-jpa https://blog.codecentric.de/en/2017/06/kotlin-spring-working-jpa-data-classes/ https://spring.io/guides/tutorials/spring-boot-kotlin/
57. Important for starters
58. Important for starters * Kotlin classes are fi nal by default
59. Important for starters * Kotlin classes are fi nal by default * Compiler plugins to the rescue!
60. Important for starters * Kotlin classes are fi nal by default * Compiler plugins to the rescue! * Data classes don’t play well with JPA
61. Important for starters * Kotlin classes are fi nal by default * Compiler plugins to the rescue! * Data classes don’t play well with JPA * Use usual classes with JPA
62. * Kotlin classes are fi nal by default * Compiler plugins to the rescue! * Data classes don’t play well with JPA * Use usual classes with JPA Important for starters * Use start.spring.io to generate con fi gs
63. kotlin extensions
67. println("hello".uuid())
68. fun String.uuid(): String = UUID.nameUUIDFromBytes(this.encodeToByteArray()).toString() println("hello".uuid())
69. fun String.uuid(): String = UUID.nameUUIDFromBytes(encodeToByteArray()).toString() println("hello".uuid())
70. fun String.uuid() = UUID.nameUUIDFromBytes(encodeToByteArray()).toString() println("hello".uuid())
71. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } }
72. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } }
73. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", RowMapper { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id)
74. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", RowMapper { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id)
75. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", RowMapper { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id)
76. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", RowMapper { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id) RowMapper is a functional interface
77. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id) “SAM conversion” is performed by the compiler
78. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }, id)
79. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id, { rs, _ -> Message(rs.getString("id"), rs.getString("text")) })
80. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id, { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }) vararg is not at the last position
81. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id, { rs, _ -> Message(rs.getString("id"), rs.getString("text")) }) Lambda expression is at the last position
82. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } }
83. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } Passing trailing lambda as a parameter to the function
84. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } }
85. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } } This is an extension function For the existing Java class in the Spring framework
86. @Service class MessageService(val db: JdbcTemplate) { fun findMessages(): List<Message> = db.query("select * from messages") { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun findMessageById(id: String): List<Message> = db.query("select * from messages where id = ?", id) { rs, _ - > Message(rs.getString("id"), rs.getString("text")) } fun post(message: Message){ db.update("insert into messages values ( ?, ? )", message.id ?: message.text.uuid(), message.text) } }
87. extensions & Trailing lambdas
88. fun String.uuid() = UUID.nameUUIDFromBytes(encodeToByteArray()).toString()
89. fun String.uuid() = UUID.nameUUIDFromBytes(encodeToByteArray()).toString() fun applyAction(vararg s: String, action: (String) -> Unit) { s.forEach(action) }
90. fun String.uuid() = UUID.nameUUIDFromBytes(encodeToByteArray()).toString() fun applyAction(vararg s: String, action: (String) -> Unit) { s.forEach(action) } fun main() { applyAction("hello", "bye") { s: String -> println(s.uuid()) } }
91. fun String.uuid() = UUID.nameUUIDFromBytes(encodeToByteArray()).toString() fun applyAction(vararg s: String, action: (String) -> Unit) { s.forEach(action) } fun main() { applyAction("hello", "bye") { s: String -> println(s.uuid()) } } Note to self: open the IDE
92. more kotlin extensions In spring
93. class HtmlController(val messageService: MessageService) { @GetMapping("/") fun index(model: Model): String { val messages = messageService.latest() model.asMap()["messages"] = messages model.asMap()["lastMessageId"] = messages.lastOrNull() ? . id ? : "" return "chat" } }
94. class HtmlController(val messageService: MessageService) { @GetMapping("/") fun index(model: Model): String { val messages = messageService.latest() model.asMap()["messages"] = messages model.asMap()["lastMessageId"] = messages.lastOrNull() ? . id ? : "" return "chat" } }
95. class HtmlController(val messageService: MessageService) { @GetMapping("/") fun index(model: Model): String { val messages = messageService.latest() model.asMap()["messages"] = messages model.asMap()["lastMessageId"] = messages.lastOrNull() ? . id ? : "" return "chat" } }
96. class HtmlController(val messageService: MessageService) { @GetMapping("/") fun index(model: Model): String { val messages = messageService.latest() model["messages"] = messages model["lastMessageId"] = messages.lastOrNull() ?. id ?: "" return "chat" } }
97. Type-safe builders A.k.a. dsl
98. @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) { addInitializers(beans) } }
99. @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) { this.addInitializers(beans) } } “this” refers to SpringApplication instance
100. val beans = beans { bean { CommandLineRunner { println("start data initialization .. . ") val repository = ref<MessageRepository>() repository.save(Message(text = "this is the first message!")) repository.save(Message(text = "this is the second")) } } } @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) { this.addInitializers(beans) } }
101. @SpringBootApplication class DemoApplication fun main(args: Array<String>) { runApplication<DemoApplication>(*args) { this.addInitializers(beans) } } val beans = beans { bean { CommandLineRunner { println("start data initialization .. . ") val repository = ref<MessageRepository>() repository.save(Message(text = "this is the first message!")) repository.save(Message(text = "this is the second } } }
102. Trailing lambdas + (extension) functions + named parameters + lambda w/ receiver = DSL fun foo(f: () -> Unit) {} fun bar(f: () -> Unit) {} fun baz(f: () -> Unit) {} fun blah(id: Int, f: Klazz.() -> Unit) {} class Klazz(var text: String) fun Klazz.hello() : String = "Hello"
103. Null safety
105. val person: Person? = getPerson() println(person.firstName) fun getPerson(): Person? {…} data class Person( var firstName: String, // … )
106. val person: Person? = getPerson() println(person.firstName) fun getPerson(): Person? {…} data class Person( var firstName: String, // … ) Can return null
107. val person: Person? = getPerson() println(person.firstName) fun getPerson(): Person? {…} data class Person( var firstName: String, // … ) Can be null
108. val person: Person? = getPerson() println(person ?. firstName) fun getPerson(): Person? {…} data class Person( var firstName: String, // … ) Null-safe dereferencing
109. val person: Person? = getPerson() println(person !! .firstName) fun getPerson(): Person? {…} data class Person( var firstName: String, // … ) “I know what I’m doing”
112. Can be null Should not be null
117. build.gradle.kts
118. Kotlin features you have seen now Type inference Inline functions Data classes Rei fi ed generics Top-level functions Named arguments Operator overloading Trailing lambdas Extension functions Functional literal with receiver Nullable types Support for JSR-305
119. Ktor
120. 2.0 is coming soon!
121. 2.0 is coming soon! An OSS framework Server & client apps Multiplatform
125. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) }
126. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Start an embedded server with Netty engine on port 8080
127. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Other options: Tomcat, Jetty, CIO
128. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Fixed port
129. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 0) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Random port
130. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 0) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Adding routes
131. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 0) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Request mapping
132. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 0) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } Write response
133. import io.ktor.server.engine.* import io.ktor.server.netty.* import io.ktor.application.* import io.ktor.response.* import io.ktor.routing.* fun main() { embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText("Hello World!") } } }.start(wait = true) } dependencies { implementation("io.ktor:ktor-server-core:$ktor_version") implementation("io.ktor:ktor-server-netty:$ktor_version") implementation("ch.qos.logback:logback-classic:$logback_version") testImplementation("io.ktor:ktor-server-tests:$ktor_version") testImplementation("org.jetbrains.kotlin:kotlin-test:$kotlin_version") } build.gradle.kts:
134. How can I do … with Ktor?
135. How can I do … with Ktor? Persistence Logging Authentication Testing Serialization Monitoring Views
136. How can I do … with Ktor? Logging Authentication Testing Serialization Monitoring JDBC / jdbi / Exposed / SQLDelight / jOOQ SLF4J, Logback, Log4j Jackson, Gson, kotlinx.serialization Views kotlinx.html, Velocity, Freemarker, Thymeleaf kotlin-test, JUnit, Testconainers Prometeus, OpenTracing Ktor * Persistence
137. Framework Toolkit VS
138. DEMO
139. YouTube.com/kotlin
140. https://speakerdeck.com/antonarhipov @antonarhipov https://youtube.com/kotlin