public class Views {
    public static class Public {}
    public static class Extended extends Public {}
}

public class Substruct
        implements JsonSerializable {

    @Override
    public void serialize(JsonGenerator jgen, SerializerProvider provider) 
            throws IOException, JsonProcessingException {
            
        serializeWithType(jgen, provider, null);
    }

    @Override
    public void serializeWithType(JsonGenerator jgen, SerializerProvider provider, TypeSerializer typeSer) 
            throws IOException, JsonProcessingException {

        if (provider.getActiveView() != null) {
            jgen.writeString(provider.getActiveView().getName());
        } else {
            jgen.writeString((String) null);
        }
    }
}

public class Struct {
        
    @JsonProperty("view")
    @JsonView(Views.Extended.class)
    public Substruct s;
}

final ObjectMapper mapper = new ObjectMapper();
        
final Struct struct = new Struct();
struct.s = new Substruct();

mapper.writeValue(System.out, struct);

{"view":null}