handle multiple JSON Objects types in a JSON Array using Retrofit2

You can create a super class which contains data common for all types and extend it:

public abstract class SuperItem {

 public enum Type {
    @SerializedName("A")
    TYPEA(1),

    @SerializedName("B")
    TYPEB(2);

    Type(final int value) {
        this.value = value;
    }

public static Type fromInteger(int i) {
        switch (i) {
            case 1:
                return TYPEA;
            case 2:
                return TYPEB;
            default:
                Log.d("SuperItem", "No existing type for integer: " + i);
                return null;
        }
    }
}

}

@SerializedName("type") private Type type;
}

public class AItem extends SuperItem {

}
public class BItem extends SuperItem {

}

Retrofit by default relies on GSON for JSON deserialization. You will need to create custom Gson deserializer for your implementation and set it to your RestAdapter:

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(SuperItem.class, new SuperItemDeserializer());
Gson gson = builder.build();
 Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .build();

Your custom deserializer can look like this:

public class SuperItemDeserializer implements     JsonDeserializer<SuperItem> {

@Override
public SuperItem deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
    Gson gson = new Gson();
    SuperItem item = null;
    JsonObject rootObject = json.getAsJsonObject();
    int typeInt = rootObject.get("type").getAsInt();
    SuperItem.Type type = SuperItem.Type.fromInteger(typeInt);
    switch (type) {
        case TYPEA:
            item = gson.fromJson(json, AItem.class);
            break;
        case TYPEB:
            item = gson.fromJson(json, BItem.class);
            break;
        default:
            Log.d("TAG", "Invalid type: " + typeInt);
    }
    return item;
}
}

Hope the naming in the example is not too bad and you'll get the idea :)