Union query requests in client code with conditional fragments

I am trying to run a query returning a union type (e.g. the union Vehicle = Car | Bike).

Is there a way to run this query with the current library? In a raw GraphQL call this would be achieved using conditional fragments like so:

query allVehicles {
    allVehicles {
        ...on Car {
            brand
        }
        ...on Bike {
            weight
        }
    }
}

I can’t seem to find a way to run the query allVehicles with the current library. Car and Bike both extend the class Vehicle, but Vehicle is a completely empty stub class.

I would expect to have a VehicleUnionResponseProjection with builder options like “.onCar(CarResponseProjection)” and ".onBike(BikeResponseProjection). Would this be possible? Or is there even currently a way to achieve this with a different apporach?

[kobylynskyi]

The feature will be released next week. Stay tuned! 😃

[elebeaup]

@kobylynskyi It is already possible to define custom serializer with customAnnotationsMapping (but I may be wrong).

For instance, the configuration

<customAnnotationsMapping>
  <Vehicle>com.fasterxml.jackson.databind.annotation.JsonDeserialize(using = com.test.jackson.VehiclesDeserializer.class</Vehicle>
</customAnnotationsMapping>

generates the following code :

public class Query implements java.io.Serializable {

    @com.fasterxml.jackson.databind.annotation.JsonDeserialize(using = com.test.jackson.VehicleDeserializer.class)
    private Vehicle allVehicles;

So, the only need is to add __typename to the projection of the union and generate the union class. For instance, like :

public class VehicleUnionResponseProjection extends GraphQLResponseProjection {

    public VehicleUnionResponseProjection() {
    }

    public VehicleUnionResponseProjection car(CarResponseProjection subProjection) {
        return car(null, subProjection);
    }

    public VehicleUnionResponseProjection car(String alias, CarResponseProjection subProjection) {
        fields.add(new GraphQLResponseField("...on Car").alias(alias).projection(subProjection));
        return this;
    }

    public VehicleUnionResponseProjection bike(BikeResponseProjection subProjection) {
        return bike(null, subProjection);
    }

    public VehicleUnionResponseProjection bike(String alias, BikeResponseProjection subProjection) {
        fields.add(new GraphQLResponseField("...on Bike").alias(alias).projection(subProjection));
        return this;
    }
}