Neighbor property TypeDeserializer for generic class

[simonhir]

I have the following generic class where i can't add the JsonTypeInfo for LockingResponse.values but only for LockingResponse.originalValues.values.
Because of the generation of the JSON that needs to be deserialized it's not possible to add the JsonTypeInfo inside the values property or above.

public class LockingResponse<E> {
    private ReadOnlyValues<E> originalValues;
    private E values;
}

public class ReadOnlyValues<E> {
    private String hash;
    @JsonTypeInfo(use = JsonTypeInfo.Id.MINIMAL_CLASS)
    private E values;
}

As the type of originalValues.values and values is the same i thought it would be possible to use that.
Problem here is that i can't get the root JsonNode inside a custom TypeDeserializer (inherited from AsPropertyTypeDeserializer) and so i can't get to the "neighbors" property.

Does someone have a better idea or knows how i can access the other property from my custom TypeDeserializer?

[cowtowncoder]

As general note, combination of generic and polymorphic types is not (and basically, can not be) supported.
And specifically type parameterization won't be available in case like this, where generic type is further required for base type of polymorphoc value.

TypeDeserializer by default does not have access to value (content) but only Type Id. In theory it can read content from JsonParser passed, but as you note it won't allow "sibling" content (especially one that has already been passed).

So what it all comes down to is that your use case would require use of custom deserializer that handles full value to which access is needed, LockingResponse.
I don't it is supportable (or ever will be) with Jackson standard polymorphic handling.

[simonhir]

Thanks for your answer.

I also tried building a custom Deserializer but didn't work out for me as i couldn't figure out how to use the ObjectMapper with a generic type.

Solution/workaround for me was to build a extra class which just extends the generic class (see following example).

public class SpecificLockingResponse extends LockingResponse<Specific> {}

[cowtowncoder]

Generic types get tricky, and although they can be made to work (SimpleModule cannot, for example, be used to register generic-relying deserializers), your work-around is a good one.