Document that configuration property binding to a Kotlin value class with a default is not supported #41693
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spring-projects-issues
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status: waiting-for-triage
mhalbritter
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mhalbritter
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type: bug
mhalbritter
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This issue also happens when value class in configuration properties and any properties have default values, not just value class property: @JvmInline
value class EntityId(val value: Int)
@ConfigurationProperties(prefix = "test")
data class AppConfig(
val entityId: EntityId,
val anotherProperty: String = "default value",
)In this case if |
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Reproducer for @FredoNook's case: package com.example
import org.springframework.boot.CommandLineRunner
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.context.properties.ConfigurationProperties
import org.springframework.boot.context.properties.EnableConfigurationProperties
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Bean
@JvmInline
value class EntityId(val value: Int)
@ConfigurationProperties(prefix = "test")
data class AppConfig(
val entityId: EntityId,
val anotherProperty: String = "default value",
)
@SpringBootApplication
@EnableConfigurationProperties(AppConfig::class)
class TestApp {
@Bean
fun runner(config: AppConfig) = CommandLineRunner {
println("Value: ${config.entityId}")
}
}
fun main(args: Array<String>) {
System.setProperty(
"SPRING_APPLICATION_JSON",
"""
{
"test": {
"entityId": 1
}
}
""".trimIndent()
)
runApplication<TestApp>(*args)
} |
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As far as I can tell, there's nothing that we can do about this as it doesn't appear to be possible to create an instance of Viewed from Java, Only one of these, the first, returns a As noted above, this works fine for a non-value class: In this case In summary, this problem appears to be a limitation of how a Kotlin value class is mapped into Java. You may want to open a Kotlin issue to see if support for working with value classes from Java can be improved. Until then, I don't think there's anything that we can do here other than documenting the limitation. We can use this issue to add something here. |
wilkinsona
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wilkinsona
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type: documentation
wilkinsona
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Affects: Spring Boot 3.3.2, Spring 6.1.11
When using a value class property in
@ConfigurationPropertieswith a default value and not providing its value in application configuration leads to an error during binding of configuration. (Tested with Kotlin 1.9.25.)Reproducer:
Running this fails with:
Ideally, this would work just like it works with defaults for non-value classes.
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