Spring Boot 3 with Kotlin throws java.lang.UnsupportedOperationException for data class on GraalVM - spring

Question

Trying to run a very simple Spring Boot 3 app on GraalVM. The app just stores some data in H2 on startup. It is basically the same as what Josh does in the Spring Tips about Ahead-of-Time compilation, but using Kotlin instead of Java.
When starting the native image, I get the following error after Spring startup:
java.lang.UnsupportedOperationException: Kotlin class com.example.demo.basics.Customer has no .copy(…) method for property id
at org.springframework.data.mapping.model.BeanWrapper$KotlinCopyUtil.setProperty(BeanWrapper.java:171) ~[na:na]
at org.springframework.data.mapping.model.BeanWrapper.setProperty(BeanWrapper.java:79) ~[na:na]
...
I'm pretty new to GraalVM and Spring Native Images, don't know if I am missing something basic which needs to be configured when using Kotlin with Spring. The missing copy methods for the data class should have been generated by Kotlin, so I guess something is left out by the native compile related to Kotlin specifically.
The code which fails is the following class:
#Configuration
class BasicsConfiguration {
#Bean // execute on application start
fun basicsApplicationListener(customerRepository: CustomerRepository): ApplicationListener<ApplicationReadyEvent> {
return ApplicationListener<ApplicationReadyEvent> {
// store some values in the database
customerRepository
.saveAll(listOf("A", "B", "C").map { Customer(null, it) })
.forEach { println(it) }
}
}
}
interface CustomerRepository : CrudRepository<Customer, Int>
data class Customer(#Id val id: Long?, val name: String)
Running the app on the JDK works perfectly fine: ./gradlew bootRun
2022-11-30T11:23:15.300+01:00 INFO 33997 --- [ main] com.example.demo.DemoApplicationKt : Started DemoApplicationKt in 2.383 seconds (process running for 2.733)
Customer(id=1, name=A)
Customer(id=2, name=B)
Customer(id=3, name=C)
The native image is also created successfully: ./gradlew nativeCompile
Starting the native image works, the server process starts up but then fails:
2022-11-30T11:08:11.085+01:00 INFO 33059 --- [ main] com.example.demo.DemoApplicationKt : Started DemoApplicationKt in 0.147 seconds (process running for 0.158)
2022-11-30T11:08:11.089+01:00 ERROR 33059 --- [ main] o.s.boot.SpringApplication : Application run failed
java.lang.UnsupportedOperationException: Kotlin class com.example.demo.basics.Customer has no .copy(…) method for property id
at org.springframework.data.mapping.model.BeanWrapper$KotlinCopyUtil.setProperty(BeanWrapper.java:171) ~[na:na]
at org.springframework.data.mapping.model.BeanWrapper.setProperty(BeanWrapper.java:79) ~[na:na]
...

Answer 1

Seems like this is an issue with Spring Data, which is not providing all necessary reflection hints for the native image creation. Specifically the reflection configuration for data classes' copy$default methods are missing. Will (probably) be fixed with Spring 6.0.3 release, see this issue for details: https://github.com/spring-projects/spring-framework/issues/29593
Workaround: add something like this in your reflect-config.json for the given data class:
{
"name": "copy$default",
"parameterTypes": [
"com.example.demo.basics.Customer",
"java.lang.Long",
"java.lang.String",
"int",
"java.lang.Object"
]
}