如何使用gson将日期序列化为long？

import com.google.gson.*;
import java.lang.reflect.Type;
import java.util.Date;

public class DateSerializer implements JsonSerializer<Date>, JsonDeserializer<Date> {
    @Override
    public JsonElement serialize(Date date, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(date.getTime());
    }

    @Override
    public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        long time = json.getAsLong();
        return new Date(time);
    }
}

Gson gson = new GsonBuilder()
        .registerTypeAdapter(Date.class, new DateSerializer())
        .create();

// 将日期序列化为long
String json = gson.toJson(date);

// 将long反序列化为日期
Date date = gson.fromJson(json, Date.class);