Gson and abstract superclasses: deserialization issue

Question

Suppose to have an abstract class, say A, and two non-abstract subclasses, say A1 and A2. I want to \"deserialize\" t

Answer 1

Following the Axxiss link, here follows the answer. A custom serializer/deserializer must be provided.

public class AClassAdapter  implements JsonSerializer<A>, JsonDeserializer<A> {
  @Override
  public JsonElement serialize(A src, Type typeOfSrc, JsonSerializationContext context) {
      JsonObject result = new JsonObject();
      result.add("type", new JsonPrimitive(src.getClass().getSimpleName()));
      result.add("properties", context.serialize(src, src.getClass())); 
      return result;
  }


  @Override
  public A deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
    JsonObject jsonObject = json.getAsJsonObject();
    String type = jsonObject.get("type").getAsString();
    JsonElement element = jsonObject.get("properties");

    try {            
        String fullName = typeOfT.getTypeName();
        String packageText = fullName.substring(0, fullName.lastIndexOf(".") + 1);

        return context.deserialize(element, Class.forName(packageText + type));
    } catch (ClassNotFoundException cnfe) {
        throw new JsonParseException("Unknown element type: " + type, cnfe);
    }
  }
}

Then the serialization is done like follows:

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(A.class, new ATypeAdapter());
String json = gson.create().toJson(list);

and given the json string, the deserialization is:

GsonBuilder gson = new GsonBuilder();
gson.registerTypeAdapter(A.class, new ATypeAdapter());

return gson.create().fromJson(json, A[].class);