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Improve Kotlin documentation

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Closes gh-22400
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Sebastien Deleuze 6 years ago
parent 514f7e3328
commit 2a0a002bd3
1 changed files with 77 additions and 78 deletions
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  1. 155
      src/docs/asciidoc/languages/kotlin.adoc

155
src/docs/asciidoc/languages/kotlin.adoc
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@ -186,15 +186,28 @@ In Java, you can, for example, write the following:
----
====
In Kotlin, with reified type parameters and `GenericApplicationContext`
Kotlin extensions, you can instead write the following:
In Kotlin, with reified type parameters and `GenericApplicationContext` Kotlin extensions,
you can instead write the following:
====
[source,kotlin,indent=0]
----
val context = GenericApplicationContext().apply {
registerBean<Foo>()
registerBean { Bar(it.getBean<Foo>()) }
registerBean { Bar(it.getBean()) }
}
----
====
If the class `Bar` has a single constructor, you can even just specify the bean class,
the constructor parameters will be autowired by type:
====
[source,kotlin,indent=0]
----
val context = GenericApplicationContext().apply {
registerBean<Foo>()
registerBean<Bar>()
}
----
====
@ -208,39 +221,23 @@ how beans are registered. The following example creates a `Play` profile:
====
[source,kotlin,indent=0]
----
fun beans() = beans {
bean<UserHandler>()
bean<Routes>()
bean<WebHandler>("webHandler") {
RouterFunctions.toWebHandler(
ref<Routes>().router(),
HandlerStrategies.builder().viewResolver(ref()).build()
)
}
bean("messageSource") {
ReloadableResourceBundleMessageSource().apply {
setBasename("messages")
setDefaultEncoding("UTF-8")
val myBeans = beans {
bean<Foo>()
bean<Bar>()
bean("bazBean") {
Baz().apply {
message = "Hello world"
}
}
bean {
val prefix = "classpath:/templates/"
val suffix = ".mustache"
val loader = MustacheResourceTemplateLoader(prefix, suffix)
MustacheViewResolver(Mustache.compiler().withLoader(loader)).apply {
setPrefix(prefix)
setSuffix(suffix)
}
}
profile("play") {
bean<Play>()
profile("foobar") {
bean { FooBar(ref("bazBean")) }
}
}
----
====
In the preceding example, `bean<Routes>()` uses autowiring by constructor, and `ref<Routes>()`
is a shortcut for `applicationContext.getBean(Routes::class.java)`.
NOTE: This DSL is programmatic, meaning it allows custom registration logic of beans
through an `if` expression, a `for` loop, or any other Kotlin constructs.
You can then use this `beans()` function to register beans on the application context,
as the following example shows:
@ -249,19 +246,16 @@ as the following example shows:
[source,kotlin,indent=0]
----
val context = GenericApplicationContext().apply {
beans().initialize(this)
myBeans.initialize(this)
refresh()
}
----
====
NOTE: This DSL is programmatic, meaning it allows custom registration logic of beans
through an `if` expression, a `for` loop, or any other Kotlin constructs.
See https://github.com/sdeleuze/spring-kotlin-functional/blob/master/src/main/kotlin/functional/Beans.kt[spring-kotlin-functional beans declaration]
for a concrete example.
See https://github.com/sdeleuze/spring-kotlin-functional[spring-kotlin-functional beans declaration] for a concrete example.
NOTE: Spring Boot is based on Java configuration and
NOTE: Spring Boot is based on JavaConfig and
https://github.com/spring-projects/spring-boot/issues/8115[does not yet provide specific support for functional bean definition],
but you can experimentally use functional bean definitions through Spring Boot's `ApplicationContextInitializer` support.
See https://stackoverflow.com/questions/45935931/how-to-use-functional-bean-definition-kotlin-dsl-with-spring-boot-and-spring-w/46033685#46033685[this Stack Overflow answer]
@ -278,8 +272,8 @@ for more details and up-to-date information.
Spring Framework now comes with a
{doc-root}/spring-framework/docs/{spring-version}/kdoc-api/spring-framework/org.springframework.web.reactive.function.server/-router-function-dsl/[Kotlin routing DSL]
that lets you use the <<web-reactive#webflux-fn,WebFlux functional
API>> to write clean and idiomatic Kotlin code, as the following example shows:
that lets you use the <<web-reactive#webflux-fn,WebFlux functional API>> to write clean and idiomatic Kotlin code,
as the following example shows:
====
[source,kotlin,indent=0]
@ -307,7 +301,7 @@ NOTE: This DSL is programmatic, meaning that it allows custom registration logic
through an `if` expression, a `for` loop, or any other Kotlin constructs. That can be useful when you need to register routes
depending on dynamic data (for example, from a database).
See https://github.com/mixitconf/mixit/tree/bad6b92bce6193f9b3f696af9d416c276501dbf1/src/main/kotlin/mixit/web/routes[MiXiT project routes]
See https://github.com/mixitconf/mixit/tree/dafd5ccc92dfab6d9c306fcb60b28921a1ccbf79/src/main/kotlin/mixit/web/routes[MiXiT project routes]
for a concrete example.
@ -583,8 +577,42 @@ all HTTP methods will be matched, not only the `GET` one.
=== Testing
This section address testing with the combination of Kotlin and the Spring Framework.
This section addresses testing with the combination of Kotlin and Spring Framework. The recommended testing framework
is https://junit.org/junit5/[JUnit 5], as well as https://mockk.io/[Mockk] for mocking.
==== Constructor injection
As described in the <<testing#testcontext-junit-jupiter-di#spring-web-reactive,dedicated section>>, JUnit 5 allows
constructor injection of beans which is pretty useful with Kotlin in order to use `val` instead of `lateinit var `.
====
[source]
----
@SpringJUnitConfig(TestConfig::class)
class OrderServiceIntegrationTests(@Autowired val orderService: OrderService,
@Autowired val customerService: CustomerService) {
// tests that use the injected OrderService and CustomerService
}
----
====
You can also use `@Autowired` at constructor level to autowire all parameters.
====
[source]
----
@SpringJUnitConfig(TestConfig::class)
class OrderServiceIntegrationTests @Autowired constructor(
val orderService: OrderService,
val customerService: CustomerService) {
// tests that use the injected OrderService and CustomerService
}
----
====
==== `PER_CLASS` Lifecycle
@ -681,20 +709,15 @@ See also the related https://jira.spring.io/browse/SPR-16057[SPR-16057] issue.
[[kotlin-getting-started]]
== Getting Started
This section describes the fastest way to get started with a project that combines
Kotlin and the Spring Framework.
The easiest way to learn how to build a Spring application with Kotlin is to follow
https://spring.io/guides/tutorials/spring-boot-kotlin/[the dedicated tutorial].
=== Using `start.spring.io`
=== `start.spring.io`
The easiest way to start a new Spring Framework 5 project in Kotlin is to create a new Spring
Boot 2 project on https://start.spring.io/#!language=kotlin[start.spring.io].
You can also create a standalone WebFlux project, as described in
https://spring.io/blog/2017/08/01/spring-framework-5-kotlin-apis-the-functional-way[this blog post].
=== Choosing the Web Flavor
@ -702,11 +725,11 @@ Spring Framework now comes with two different web stacks: <<web#mvc,Spring MVC>>
<<web-reactive#spring-web-reactive,Spring WebFlux>>.
Spring WebFlux is recommended if you want to create applications that will deal with latency,
long-lived connections, o streaming scenarios or if you want to use the web functional
long-lived connections, streaming scenarios or if you want to use the web functional
Kotlin DSL.
For other use cases, especially if you are using blocking technologies such as JPA, Spring
MVC and its annotation-based programming model is a perfectly valid and fully supported choice.
MVC and its annotation-based programming model is the recommended choice.
@ -724,27 +747,6 @@ Kotlin and the Spring Framework:
* https://kotlin.link/[Awesome Kotlin]
=== Tutorials
We recommend the following tutorials:
* https://spring.io/guides/tutorials/spring-boot-kotlin/[Building web applications with Spring Boot and Kotlin]
* https://kotlinlang.org/docs/tutorials/spring-boot-restful.html[Creating a RESTful Web Service with Spring Boot]
=== Blog posts
The following blog posts provide further details:
* https://spring.io/blog/2016/02/15/developing-spring-boot-applications-with-kotlin[Developing Spring Boot applications with Kotlin]
* https://spring.io/blog/2016/03/20/a-geospatial-messenger-with-kotlin-spring-boot-and-postgresql[A Geospatial Messenger with Kotlin, Spring Boot and PostgreSQL]
* https://spring.io/blog/2017/01/04/introducing-kotlin-support-in-spring-framework-5-0[Introducing Kotlin support in Spring Framework 5.0]
* https://spring.io/blog/2017/08/01/spring-framework-5-kotlin-apis-the-functional-way[Spring Framework 5 Kotlin APIs, the functional way]
=== Examples
The following Github projects offer examples that you can learn from and possibly even extend:
@ -764,22 +766,19 @@ The following Github projects offer examples that you can learn from and possibl
The following list categorizes the pending issues related to Spring and Kotlin support:
* Spring Framework
** https://jira.spring.io/browse/SPR-16057[Unable to use WebTestClient with mock server in Kotlin]
** https://jira.spring.io/browse/SPR-15942[Support null-safety at generics, varargs and array elements level]
** https://jira.spring.io/browse/SPR-15413[Add support for Kotlin coroutines]
** https://github.com/spring-projects/spring-framework/issues/20606[Unable to use WebTestClient with mock server in Kotlin]
** https://github.com/spring-projects/spring-framework/issues/20496[Support null-safety at generics, varargs and array elements level]
** https://github.com/spring-projects/spring-framework/issues/19975[Add support for Kotlin coroutines]
* Spring Boot
** https://github.com/spring-projects/spring-boot/issues/8762[Allow `@ConfigurationProperties` binding for immutable POJOs]
** https://github.com/spring-projects/spring-boot/issues/1254[Allow `@ConfigurationProperties` binding on interfaces]
** https://github.com/spring-projects/spring-boot/issues/8115[Expose the functional bean registration API via `SpringApplication`]
** https://github.com/spring-projects/spring-boot/issues/10712[Add null-safety annotations on Spring Boot APIs]
** https://github.com/spring-projects/spring-boot/issues/9486[Use Kotlin's bom to provide dependency management for Kotlin]
* Kotlin
** https://youtrack.jetbrains.com/issue/KT-6380[Parent issue for Spring Framework support]
** https://youtrack.jetbrains.com/issue/KT-5464[Kotlin requires type inference where Java doesn't]
** https://github.com/Kotlin/KEEP/issues/79[Better generics null-safety support]
** https://youtrack.jetbrains.com/issue/KT-20283[Smart cast regression with open classes]
** https://youtrack.jetbrains.com/issue/KT-14984[Impossible to pass not all SAM argument as function]
** https://youtrack.jetbrains.com/issue/KT-19592[Apply JSR 305 meta-annotations to generic type parameters]
** https://youtrack.jetbrains.com/issue/KT-18398[Provide a way for libraries to avoid mixing Kotlin 1.0 and 1.1 dependencies]
** https://youtrack.jetbrains.com/issue/KT-15125[Support JSR 223 bindings directly via script variables]
** https://youtrack.jetbrains.com/issue/KT-15467[Support all-open and no-arg compiler plugins in Kotlin Eclipse plugin]
** https://youtrack.jetbrains.com/issue/KT-6653[Kotlin properties do not override Java-style getters and setters]

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