de-/serialize enums by ordinal with GSON

GsonEnumByOrdinalSerializer.java

package com.denisandrejew.util;

import com.google.gson.*;
import lombok.experimental.var; // if java < 10

import java.lang.reflect.Type;

public class GsonEnumByOrdinalSerializer<T extends Enum> implements JsonSerializer<T>, JsonDeserializer<T> {
    @Override
    public T deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) throws JsonParseException {
        try {
            var cls = Class.forName(type.getTypeName());
            var types = cls.getEnumConstants();
            var ord = jsonElement.getAsInt();
            return ord <= types.length && ord >= 1 ? (T) types[ord - 1] : null;
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e); // fancy error handling here
        }
    }

    @Override
    public JsonElement serialize(T item, Type type, JsonSerializationContext jsonSerializationContext) {
        return item == null ? JsonNull.INSTANCE : new JsonPrimitive(item.ordinal());
    }
}

usage.md

public enum MyEnum {
  ONE, TWO;
}

Gson gson = new GsonBuilder()
            .registerTypeAdapter(MyEnum.class, new GsonEnumByOrdinalSerializer<>())
            .create();