Spring Validation of JSON - Why do I need to add `#field` - spring

Question

I've finally made some progress on Spring validation (on a JSON object coming in from RabbitMQ).
However there are a couple of things I don't understand:
In the documentation, it states I can just use the annotation #NotBlank then in my method I use the annotation #Valid. However I find this wasn't doing anything. So instead I did #field:NotBlank and it worked together with the following - why did this #field do the trick?
#JsonIgnoreProperties(ignoreUnknown = true)
data class MyModel (
#field:NotBlank(message = "ID cannot be blank")
val id : String = "",
#field:NotBlank(message = "s3FilePath cannot be blank")
val s3FilePath : String = ""
)
Then the function using this model:
#Service
class Listener {
#RabbitListener(queues = ["\${newsong.queue}"])
fun received(data: MyModel) {
val factory = Validation.buildDefaultValidatorFactory()
val validator = factory.validator
val validate = validator.validate(data)
// Then this `validate` will return an array of validation errors
println(validate)
}
}
Correct me if I'm wrong however I assumed just using #Valid and this point fun received(#Valid data: MyModel) it would just throw some exception for me to catch - any idea based on my code why this could have been?
Any advice/help would be appreciated.
Thanks.
Here are the imports:
import com.fasterxml.jackson.annotation.JsonIgnoreProperties
import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Service
import javax.validation.*
import org.springframework.amqp.rabbit.core.RabbitTemplate
import org.springframework.amqp.rabbit.annotation.RabbitListener
import javax.validation.constraints.NotBlank

Answer 1

Quoting Kotlin's documentation for annotations:
When you're annotating a property or a primary constructor parameter, there are multiple Java elements which are generated from the corresponding Kotlin element, and therefore multiple possible locations for the annotation in the generated Java bytecode. To specify how exactly the annotation should be generated, use the following syntax:
class Example(#field:Ann val foo, // annotate Java field
#get:Ann val bar, // annotate Java getter
#param:Ann val quux) // annotate Java constructor parameter
So, until explicitly mention what you are annotating (field, getter or something else) in Kotlin class constructor, it won't automatically know where you want to put that annotation.