pojo support for query / mutation parameter

[cryptoki]

up to version 5.x we could use our Java Pojos

public class SomeOldPojo {
  public String value;
}

  fun pojo(pojo: SomeOldPojo): String? = "hello ${pojo.value}"

query {
	pojo(pojo: {value: "abc"})
}

with the 6.x release the Jackson ObjectMapper is removed and therewith the java support. Is there a best practice to use / integrate old pojo?

little playground https://github.com/cryptoki/graphql-defaults

[dariuszkuc]

Hello 👋
While Jackson is no longer used for object serialization/deserialization, POJOs should still be handled in the same way*.

*by using Java POJOs you are missing nullability information

[cryptoki]

@dariuszkuc thank you. what do you mean with in the same way?

If I'm using Java POJOs in the same way as I used it with graphql-kotlin 5.x.x I've got the following error

com.expediagroup.graphql.generator.exceptions.PrimaryConstructorNotFound: Invalid input object SomeOldPojo - missing public primary constructor

v5.x.x works well with the inside Jackson mapper.

[cryptoki]

add on info.
we can't migration these Java POJOs to Kotlin. It's important to use the same java classes. We have a lot of services with java/groovy code using these POJOs.

[dariuszkuc]

@cryptoki correction, yes it is not in the "same" way as instead of reflections and Jackson we are now using constructor to pass in the parameters. Your exception states your POJO classes do not specify the appropriate primary constructor.

[cryptoki]

@dariuszkuc java classes does not have a primary constructor.

how can we integrate / using our existing java pojo classes? It's important. see my little playground project linked in the top post.

query {
  pojo(pojo: {value: "abc"})
}

[dariuszkuc]

Looks like primary constructor designation is from Kotlin, so Java classes won't provide this metadata. We could potentially update our logic from

var targetConstructor = targetClass.primaryConstructor ?: throw PrimaryConstructorNotFound(targetClass)

to something like

var targetConstructor = targetClass.primaryConstructor
if (targetConstructor == null && targetClass.constructors.size == 1) {
  targetConstructor = targetClass.constructors.first()
}
if (targetConstructor == null) {
  throw PrimaryConstructorNotFound(targetClass)
}

This would still be somewhat limited (i.e. expects single all-args constructor as POJOs are system-types so their fields are considered non-null and required).

@samuelAndalon thoughts?

[samuelAndalon]

Yes, we will have the limitation of the lack of nullability info, all arguments are going to be considered required and non-null, but i think we can keep the supporting POJOs constructor after removing the usage of object mapper --
i can work in the fix.

[samuelAndalon]

as discussed we will provide support for non primary constructors, if multiple constructors found, an exception will be thrown, you can keep using POJOs but you will have to specify at least 1 constructor.
As of now we are not going to provide support for matching properties which is something non trivial.