[Java] Generator produces a dedicated field for the discriminator

Origin: https://stackoverflow.com/q/50163882/131929

Is it correct that the generator produces a dedicated field for the discriminator?

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "errorType", visible = true)
@JsonSubTypes({
    @JsonSubTypes.Type(value = SpecificError.class, name = "SpecificError"),
})
public class GeneralError {
    @JsonProperty("errorType")
    private String errorType = null;
    ...

errorType is the declared discriminator.

When Jackson serializes a SpecificError object it includes errorType twice:

{"errorType":"SpecificError","message":"message","errorType":null}

Start by reproducing the generated Java model from the issue with Jackson serialization, then trace how the Java generator handles the declared discriminator and its corresponding field. Confirm whether the discriminator is emitted twice and identify the generator template or logic responsible; done means the generated model no longer serializes duplicate errorType properties.