How can I configure a JAX-RS application in Kotlin with resources having other dependencies injected - kotlin

Question

I use JAX-RS to build a REST API. To bootstrap all resources I have a overridden an "Application":
import javax.enterprise.context.ApplicationScoped;
import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;
#ApplicationScoped
#ApplicationPath("/")
open class ApiConfig : Application() {
override fun getSingletons(): MutableSet<Any> {
println("----- init jaxrs -----")
return mutableSetOf(EchoResource())
}
}
As you can see I register the EchoResource() with brackets. It does not work when I use EchoResource::class.
My Problem is, that I want to inject some service into EchoResource:
import dev.elysion.mail.smtp.MailService
import javax.enterprise.context.RequestScoped
import javax.inject.Inject
import javax.ws.rs.GET
import javax.ws.rs.Path
#Path("/echo")
#RequestScoped
class EchoResource #Inject constructor(private val mailService: MailService) {
#GET
fun getHello(): String {
return "Hello World"
}
}
When I add the constructor I get an error in API Config saying that I do not pass a parameter for MailService.
In Java I would register the resource with EchoResource.class which does not care about any parameters.
How can I achieve the same with Kotlin?

Answer 1

It works if getClasses() is used instead of getSingletons():
import javax.enterprise.context.ApplicationScoped
import javax.ws.rs.ApplicationPath
import javax.ws.rs.core.Application
#ApplicationScoped
#ApplicationPath("/")
open class ApiConfig : Application() {
override fun getClasses(): MutableSet<Class<*>> {
return mutableSetOf(EchoResource::class.java)
}
}
Furthermore, all resources and all of their methods need to be open (not final) in order to be proxyable for CDI.