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Spring ❤️ Kotlin #jjug
The document discusses Kotlin support in Spring Framework 5. It covers how Kotlin can be used with Spring Boot and Spring's programming model through features like extension functions and reified type parameters. It provides code examples of using Kotlin idioms with Spring components like the application context, JdbcTemplate, and RestTemplate to make the code more concise and readable. It also briefly mentions new features in Spring Framework 5 like reactive support using Spring WebFlux and using router functions with Kotlin.
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Spring ❤️ Kotlin #jjug
- 1.‹#›© 2016 PivotalSoftware, Inc. All rights reserved. ‹#›© 2016 Pivotal Software, Inc. All rights reserved.Spring ❤ KotlinToshiaki Maki (@making)tmaki@pivotal.ioJJUG Night Seminar 2017 Feb2017-02-20
- 2.© 2016 PivotalSoftware, Inc. All rights reserved.Who am I ?• Toshiaki Maki (@making) https://ik.am• Sr. Solutions Architect @Pivotal• Spring ☘ / Cloud Foundry ☁ / Concourse ✈ / BOSH 🐚bit.ly/hajiboot2
- 3.© 2016 PivotalSoftware, Inc. All rights reserved.Agenda•Spring Boot with Kotlin•Kotlin support in Spring 5
- 4.‹#›© 2016 PivotalSoftware, Inc. All rights reserved.Spring Boot with Kotlin
- 5.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Initializr
- 6.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Initializr
- 7.© 2016 PivotalSoftware, Inc. All rights reserved.
- 8.© 2016 PivotalSoftware, Inc. All rights reserved.
- 9.© 2016 PivotalSoftware, Inc. All rights reserved.
- 10.© 2016 PivotalSoftware, Inc. All rights reserved.
- 11.© 2016 PivotalSoftware, Inc. All rights reserved.
- 12.© 2016 PivotalSoftware, Inc. All rights reserved.
- 13.© 2016 PivotalSoftware, Inc. All rights reserved.
- 14.© 2016 PivotalSoftware, Inc. All rights reserved.package com.example import org.springframework.boot.SpringApplication import org.springframework.boot.autoconfigure.SpringBootApplication @SpringBootApplication class DemoApplication fun main(args: Array<String>) { SpringApplication.run(DemoApplication::class.java, *args) }
- 15.© 2016 PivotalSoftware, Inc. All rights reserved.
- 16.© 2016 PivotalSoftware, Inc. All rights reserved.package com.example import org.springframework.web.bind.annotation.GetMapping import org.springframework.web.bind.annotation.RestController @RestController class HelloController { @GetMapping("/") fun hello() = "Hello World!" }
- 17.© 2016 PivotalSoftware, Inc. All rights reserved.package com.example import org.springframework.web.bind.annotation.GetMapping import org.springframework.web.bind.annotation.RestController @RestController class HelloController { @GetMapping("/") fun hello() = "Hello World!" }
- 18.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinopen class AppConfig { @Bean open fun restTemplate() = RestTemplate() }
- 19.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinopen class AppConfig { @Bean open fun restTemplate() = RestTemplate() }👇👇
- 20.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinopen class AppConfig { @Bean open fun restTemplate() = RestTemplate() }👇👇😩
- 21.© 2016 PivotalSoftware, Inc. All rights reserved.Cglib and Spring// Javaclass AppConfig { @Bean RestTemplate restTemplate() {return new RestTemplate();} }
- 22.© 2016 PivotalSoftware, Inc. All rights reserved.Cglib and Spring// Javaclass AppConfig { @Bean RestTemplate restTemplate() {return new RestTemplate();} }Singleton
- 23.© 2016 PivotalSoftware, Inc. All rights reserved.Cglib and Spring (Pseudo Code)class AppConfig$$ extends AppConfig {@Override RestTemplate restTemplate() {if (context.contains("restTemplate")) {return context.get("restTemplate");}return super.restTemplate();} }
- 24.© 2016 PivotalSoftware, Inc. All rights reserved.Cglib and Spring (Pseudo Code)class AppConfig$$ extends AppConfig {@Override RestTemplate restTemplate() {if (context.contains("restTemplate")) {return context.get("restTemplate");}return super.restTemplate();} }Methods in Kotlinare final by default !!open removes final
- 25.© 2016 PivotalSoftware, Inc. All rights reserved.<plugin> <artifactId>kotlin-maven-plugin</artifactId> <groupId>org.jetbrains.kotlin</groupId> <version>${kotlin.version}</version> <configuration> <compilerPlugins> <plugin>spring</plugin> </compilerPlugins> </configuration></plugin>
- 26.© 2016 PivotalSoftware, Inc. All rights reserved.open class AppConfig { @Bean open fun restTemplate() = RestTemplate() }
- 27.© 2016 PivotalSoftware, Inc. All rights reserved.open class AppConfig { @Bean open fun restTemplate() = RestTemplate() }
- 28.© 2016 PivotalSoftware, Inc. All rights reserved.class AppConfig { @Bean fun restTemplate() = RestTemplate() }
- 29.© 2016 PivotalSoftware, Inc. All rights reserved.class AppConfig { @Bean fun restTemplate() = RestTemplate() }😍
- 30.© 2016 PivotalSoftware, Inc. All rights reserved.http://start.spring.io/#!language=kotlin
- 31.‹#›© 2016 PivotalSoftware, Inc. All rights reserved.Kotlin support in Spring 5
- 32.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Framework 5•Java 8 baseline, Java 9 compatibility•Reactive Support & Spring WebFlux•Router Functions•Performance improvements•HTTP/2 support•Kotlin support
- 33.© 2016 PivotalSoftware, Inc. All rights reserved.Kotlin Support
- 34.© 2016 PivotalSoftware, Inc. All rights reserved.Kotlin Support
- 35.© 2016 PivotalSoftware, Inc. All rights reserved.Kotlin Support•Extension Functions•Reified type parameters
- 36.© 2016 PivotalSoftware, Inc. All rights reserved.Kotlin Support•Extension Functions•Reified type parameters🤔
- 37.© 2016 PivotalSoftware, Inc. All rights reserved.package com.example;public class Foo {public <T> T create(Class<T> clazz) {try {return clazz.newInstance();}catch (Exception e) {throw new IllegalStateException(e);}}}
- 38.© 2016 PivotalSoftware, Inc. All rights reserved.// JavaFoo foo = new Foo();Bar bar = foo.create(Bar.class);
- 39.© 2016 PivotalSoftware, Inc. All rights reserved.// JavaFoo foo = new Foo();Bar bar = foo.create(Bar.class);// Kotlinval foo = Foo()val bar = foo.create(Bar::class.java)
- 40.© 2016 PivotalSoftware, Inc. All rights reserved.// JavaFoo foo = new Foo();Bar bar = foo.create(Bar.class);// Kotlinval foo = Foo()val bar = foo.create(Bar::class.java)👇
- 41.© 2016 PivotalSoftware, Inc. All rights reserved.KClassBar::class // kotlin.reflect.KClassBar::class.java // java.lang.Class
- 42.© 2016 PivotalSoftware, Inc. All rights reserved.Extension Functions•Extends a class with new functionalitywithout having to inherit from the class•https://kotlinlang.org/docs/reference/extensions.html#extension-functions
- 43.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinval foo = Foo()val bar = foo.create(Bar::class.java)
- 44.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinval foo = Foo()val bar = foo.create(Bar::class.java)
- 45.© 2016 PivotalSoftware, Inc. All rights reserved.// Kotlinval foo = Foo()val bar = foo.create(Bar::class)
- 46.© 2016 PivotalSoftware, Inc. All rights reserved.Extension Functions// Kotlinval foo = Foo()val bar = foo.create(Bar::class)
- 47.© 2016 PivotalSoftware, Inc. All rights reserved.Extension Functionspackage com.exampleimport kotlin.reflect.KClassfun <T : Any> Foo.create(kclass: KClass<T>)= create(kclass.java) FooExtensions.kt
- 48.© 2016 PivotalSoftware, Inc. All rights reserved.Extension Functionspackage com.exampleimport kotlin.reflect.KClassfun <T : Any> Foo.create(kclass: KClass<T>)= create(kclass.java) 👇FooExtensions.kt
- 49.© 2016 PivotalSoftware, Inc. All rights reserved.Extension Functions// Kotlinval foo = Foo()val bar = foo.create(Bar::class)😍
- 50.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parameters•Access a type passed to us as a parameter•https://kotlinlang.org/docs/reference/inline-functions.html#reified-type-parameters
- 51.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parametersinline fun <reified T : Any> Foo.create()= create(T::class.java)
- 52.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parametersinline fun <reified T : Any> Foo.create()= create(T::class.java) 👇👇
- 53.© 2016 PivotalSoftware, Inc. All rights reserved.val foo = Foo()val bar = foo.create(Bar::class)
- 54.© 2016 PivotalSoftware, Inc. All rights reserved.val foo = Foo()val bar = foo.create(Bar::class)
- 55.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parametersval foo = Foo()val bar = foo.create<Bar>() 😍
- 56.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parametersval foo = Foo()val bar: Bar = foo.create() 😍
- 57.© 2016 PivotalSoftware, Inc. All rights reserved.Reified type parametersval foo = Foo()val bar: Bar = foo.create() 😍"idiomatic Kotlin code"
- 58.© 2016 PivotalSoftware, Inc. All rights reserved."idiomatic Kotlin code" with Spring 5
- 59.© 2016 PivotalSoftware, Inc. All rights reserved.Application Context// JavaApplicationContext context = ...;Bar bar = context.getBean(Bar.class);
- 60.© 2016 PivotalSoftware, Inc. All rights reserved.Application Context (Extension)// Kotlinval context = ...val bar = context.getBean(Bar::class)
- 61.© 2016 PivotalSoftware, Inc. All rights reserved.Application Context (Reified Type)// Kotlinval context = ...val bar = context.getBean<Bar>()
- 62.© 2016 PivotalSoftware, Inc. All rights reserved.Application Context (Reified Type)// Kotlinval context = ...val bar: Bar = context.getBean()
- 63.© 2016 PivotalSoftware, Inc. All rights reserved.JdbcTemplate// JavaLong count = jdbcTemplate.queryForObject("SELECT count(*) FROM foo", Long.class);
- 64.© 2016 PivotalSoftware, Inc. All rights reserved.JdbcTemplate (Extension)// Kotlinval count = jdbcTemplate.queryForObject("SELECT count(*) FROM foo", Long::class)
- 65.© 2016 PivotalSoftware, Inc. All rights reserved.JdbcTemplate (Reified Type)// Kotlinval count = jdbcTemplate.queryForObject<Long>("SELECT count(*) FROM foo")
- 66.© 2016 PivotalSoftware, Inc. All rights reserved.JdbcTemplate (Reified Type)// Kotlinval count: Long = jdbcTemplate.queryForObject("SELECT count(*) FROM foo")
- 67.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate// JavaString foo = restTemplate.getForObject("http://abc.io",String.class);
- 68.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate (Reified Type)// Kotlinval foo = restTemplate.getForObject<String>("http://abc.io");
- 69.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate (Reified Type)// Kotlinval foo: String = restTemplate.getForObject("http://abc.io");
- 70.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate// JavaList<Foo> foos = restTemplate.getForObject("http://abc.io",List<Foo>.class);
- 71.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate// JavaList<Foo> foos = restTemplate.getForObject("http://abc.io",List<Foo>.class);Compile Error!
- 72.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate// JavaList<Foo> foos = restTemplate.exchange("http://abc.io", HttpMethod.GET,null, newParameterizedTypeReference<List<Foo>>(){}).getBody();
- 73.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate// JavaList<Foo> foos = restTemplate.exchange("http://abc.io", HttpMethod.GET,null, newParameterizedTypeReference<List<Foo>>(){}).getBody();💩
- 74.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate (Reified Type)
- 75.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate (Reified Type)// Kotlinval foos: List<Foo> = restTemplate.getForObject("http://abc.io");
- 76.© 2016 PivotalSoftware, Inc. All rights reserved.RestTemplate (Reified Type)// Kotlinval foos: List<Foo> = restTemplate.getForObject("http://abc.io");😍
- 77.© 2016 PivotalSoftware, Inc. All rights reserved.Spring ❤ Kotlin
- 78.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Framework 5•Java 8 baseline, Java 9 compatibility•Reactive Support & Spring WebFlux•Router Functions•Performance improvements•HTTP/2 support•Kotlin support
- 79.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Framework 5•Java 8 baseline, Java 9 compatibility•Reactive Support & Spring WebFlux•Router Functions•Performance improvements•HTTP/2 support•Kotlin support👇👇
- 80.© 2016 PivotalSoftware, Inc. All rights reserved.Spring Framework 5•Java 8 baseline, Java 9 compatibility•Reactive Support & Spring WebFlux•Router Functions•Performance improvements•HTTP/2 support•Kotlin support👇👇🤔
- 81.© 2016 PivotalSoftware, Inc. All rights reserved.
- 82.© 2016 PivotalSoftware, Inc. All rights reserved.WebMVC + @Controller in Java@RestControllerpublic class UserController {private final UserRepository repo;UserController(UserRepository repo) {/.../}@GetMappingList<User> users() {return repo.findAll();}}
- 83.© 2016 PivotalSoftware, Inc. All rights reserved.WebFlux + @Controller in Java@RestControllerpublic class UserController {private final ReactiveUserRepository repo;UserController(ReactiveUserRepository repo) {/.../}@GetMappingFlux<User> users() {return repo.findAll();}}
- 84.© 2016 PivotalSoftware, Inc. All rights reserved.WebFlux + @Controller in Java@RestControllerpublic class UserController {private final ReactiveUserRepository repo;UserController(ReactiveUserRepository repo) {/.../}@GetMappingFlux<User> users() {return repo.findAll();}}Non-Blocking!!
- 85.© 2016 PivotalSoftware, Inc. All rights reserved.WebFlux + RouterFunction in Java
- 86.© 2016 PivotalSoftware, Inc. All rights reserved.WebFlux + RouterFunction in JavaRouterFunction<?> routes =route(GET("/users"), req -> ok().body(repo.findAll(), User.class));
- 87.© 2016 PivotalSoftware, Inc. All rights reserved.WebFlux + RouterFunction in Kotlin{accept(APPLICATION_JSON).apply {GET("/users",{ok().body(fromPublisher(repo.findAll())})}}
- 88.© 2016 PivotalSoftware, Inc. All rights reserved.Check source code!!• https://github.com/mix-it/mixit• https://github.com/making/demo-router-functions
- 89.© 2016 PivotalSoftware, Inc. All rights reserved.Other Kotlin Support•Functional Bean Registration with Kotlin•WebFlux functional API, the Kotlin way•Leveraging Kotlin nullable information•Kotlin Script based templates•...•https://speakerdeck.com/sdeleuze/functional-web-applications-with-kotlin-and-spring-5?
- 90.© 2016 PivotalSoftware, Inc. All rights reserved.Release datehttps://jira.spring.io/browse/SPR
- 91.© 2016 PivotalSoftware, Inc. All rights reserved.http://start.spring.io/#!language=kotlin
- 92.© 2016 PivotalSoftware, Inc. All rights reserved.http://start.spring.io/#!language=kotlin
- 93.© 2016 PivotalSoftware, Inc. All rights reserved.http://start.spring.io/#!language=kotlin
- 94.© 2016 PivotalSoftware, Inc. All rights reserved.http://start.spring.io/#!language=kotlin
- 95.© 2016 PivotalSoftware, Inc. All rights reserved.Resources• https://spring.io/blog/2017/01/04/introducing-kotlin-support-in-spring-framework-5-0• https://speakerdeck.com/sdeleuze• https://blog.ik.am/entries/407
- 96.© 2016 PivotalSoftware, Inc. All rights reserved.CfP for JJUG CCC 2017 Spring•Submit Call for Paper!!! 🙇•http://www.java-users.jp/?p=2830