This version is still in development and is not considered stable yet. For the latest stable version, please use Spring Framework 6.1.14! |
Web
Router DSL
Spring Framework comes with a Kotlin router DSL available in 3 flavors:
These DSL let you write clean and idiomatic Kotlin code to build a RouterFunction
instance as the following example shows:
@Configuration
class RouterRouterConfiguration {
@Bean
fun mainRouter(userHandler: UserHandler) = router {
accept(TEXT_HTML).nest {
GET("/") { ok().render("index") }
GET("/sse") { ok().render("sse") }
GET("/users", userHandler::findAllView)
}
"/api".nest {
accept(APPLICATION_JSON).nest {
GET("/users", userHandler::findAll)
}
accept(TEXT_EVENT_STREAM).nest {
GET("/users", userHandler::stream)
}
}
resources("/**", ClassPathResource("static/"))
}
}
This DSL is programmatic, meaning that it allows custom registration logic of beans
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).
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See MiXiT project for a concrete example.
MockMvc DSL
A Kotlin DSL is provided via MockMvc
Kotlin extensions in order to provide a more
idiomatic Kotlin API and to allow better discoverability (no usage of static methods).
val mockMvc: MockMvc = ...
mockMvc.get("/person/{name}", "Lee") {
secure = true
accept = APPLICATION_JSON
headers {
contentLanguage = Locale.FRANCE
}
principal = Principal { "foo" }
}.andExpect {
status { isOk }
content { contentType(APPLICATION_JSON) }
jsonPath("$.name") { value("Lee") }
content { json("""{"someBoolean": false}""", false) }
}.andDo {
print()
}
Kotlin Script Templates
Spring Framework provides a
ScriptTemplateView
which supports JSR-223 to render templates by using script engines.
By leveraging scripting-jsr223
dependencies, it
is possible to use such feature to render Kotlin-based templates with
kotlinx.html DSL or Kotlin multiline interpolated String
.
build.gradle.kts
dependencies {
runtime("org.jetbrains.kotlin:kotlin-scripting-jsr223:${kotlinVersion}")
}
Configuration is usually done with ScriptTemplateConfigurer
and ScriptTemplateViewResolver
beans.
KotlinScriptConfiguration.kt
@Configuration
class KotlinScriptConfiguration {
@Bean
fun kotlinScriptConfigurer() = ScriptTemplateConfigurer().apply {
engineName = "kotlin"
setScripts("scripts/render.kts")
renderFunction = "render"
isSharedEngine = false
}
@Bean
fun kotlinScriptViewResolver() = ScriptTemplateViewResolver().apply {
setPrefix("templates/")
setSuffix(".kts")
}
}
See the kotlin-script-templating example project for more details.
Kotlin multiplatform serialization
Kotlin multiplatform serialization is supported in Spring MVC, Spring WebFlux and Spring Messaging (RSocket). The builtin support currently targets CBOR, JSON, and ProtoBuf formats.
To enable it, follow those instructions to add the related dependency and plugin.
With Spring MVC and WebFlux, both Kotlin serialization and Jackson will be configured by default if they are in the classpath since
Kotlin serialization is designed to serialize only Kotlin classes annotated with @Serializable
.
With Spring Messaging (RSocket), make sure that neither Jackson, GSON or JSONB are in the classpath if you want automatic configuration,
if Jackson is needed configure KotlinSerializationJsonMessageConverter
manually.