Use a custom deserializer only on fields? - gson

Question

I do a replication mechanism where I synchronize two databases. For communicating between databases I serialize the objects into JSON using Gson. Each object has a UUID to identify it. To avoid having to send the items that are up to date I use the objects UUID when an object is included in a field in an object to be replicated.
We got the following classes:
public class Entity {
String uuid;
// Getters and setters..
}
public class Article extends Entity {
String name;
Brand brand;
// Getters and setters..
}
public class Brand extens Entity {
String name;
Producer producer
// Getters and setters..
}
public class Producer extends Entity {
String name;
// Getters and setters..
}
If I serialize Article its JSON representation will look like this:
{"brand":"BrandÖ179d7798-aa63-4dd2-8ff6-885534f99e77","uuid":"5dbce9aa-4129-41b6-a8e5-d3c030279e82","name":"Sun-Maid"}
where "BrandÖ179d7798-aa63-4dd2-8ff6-885534f99e77" is the class ("Brand") and the UUID.
If I serialize Brand I expect:
{"producer":"ProducerÖ173d7798-aa63-4dd2-8ff6-885534f84732","uuid":"5dbce9aa-4129-41b6-a8e5-d3c0302w34w2","name":"Carro"}
In Jackson I would change Article class to:
public class Article {
String uuid;
String name;
#JsonDeserialize (using = EntityUUIDDeserializer.class) # JsonSerialize (using = EntityUUIDSerializer.class)
Brand brand;
// Getters and setters..
}
and implement custom serializer and deserializer to return the UUID instead of the object.
Gson do not have a #JsonDeserialize annotation.
If we install the serializer and deserializer doing like this:
Gson gson = new GsonBuilder()
.registerTypeAdapter(Producer.class, new EntityUUIDDeserializer())
.registerTypeAdapter(Brand.class, new EntityUUIDDeserializer())
.registerTypeAdapter/Producer.class, new EntityUUIDSerializer())
.registerTypeAdapter(Brand.class, new EntityUUIDSerializer())
.create();
We can serialize Article and Brand ok.
Deserialize Article by
Article article= gson.fromJson(inputJSONString, Article.class);
works fine but
Brand brand= gson.fromJson(inputJSONString, Brand.class);
do not work. I guess the probem is that when we deserialize a Brand we get the deserializer for Brand to kick in trying to return an UUID string, but we want the deserializer to return a Brand-object instead.
Is there a way to avoid creating two different Gson objects? The problem with two diffrent Gson objects is when you want to deserialize an object that contains both Article and Brand.

Answer 1

You write the serializer/deserializer and register it with Gson (using the GsonBuilder).
https://sites.google.com/site/gson/gson-user-guide#TOC-Custom-Serialization-and-Deserialization
Gson g = new GsonBuilder()
.registerTypeAdapter(Producer.class, new MyProducerDeserializer())
.registerTypeAdapter(Producer.class, new MyProducerSerializer())
.create();
When you serialize/deserialize your Brand class, it will use them for the Producer field contained therein.