InterfaceAdapter.java

package network.thunder.core.communication.objects.messages.impl;

import com.google.gson.*;

import java.lang.reflect.Type;

final class InterfaceAdapter <T> implements JsonSerializer<T>, JsonDeserializer<T> {

    @Override
    public JsonElement serialize (T object, Type interfaceType, JsonSerializationContext context) {
        final JsonObject wrapper = new JsonObject();
        wrapper.addProperty("type", object.getClass().getName());
        wrapper.add("data", new Gson().toJsonTree(object));
        return wrapper;
    }

    public T deserialize (JsonElement elem, Type interfaceType, JsonDeserializationContext context) throws JsonParseException {
        final JsonObject wrapper = (JsonObject) elem;
        final JsonElement typeName = get(wrapper, "type");
        final JsonElement data = get(wrapper, "data");
        final Type actualType = typeForName(typeName);
        return context.deserialize(data, actualType);
    }

    private Type typeForName (final JsonElement typeElem) {
        try {
            return Class.forName(typeElem.getAsString());
        } catch (ClassNotFoundException e) {
            throw new JsonParseException(e);
        }
    }

    private JsonElement get (final JsonObject wrapper, String memberName) {
        final JsonElement elem = wrapper.get(memberName);
        if (elem == null) {
            throw new JsonParseException("no '" + memberName + "' member found in what was expected to be an interface wrapper");
        }
        return elem;
    }
}