Message.java

/*
 * ShootOFF - Software for Laser Dry Fire Training
 * Copyright (C) 2016 phrack
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package com.shootoff.headless.protocol;

import java.lang.reflect.Type;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class Message {
	private static final Gson gson;

	static {
		gson = new GsonBuilder().registerTypeAdapter(Message.class, new InterfaceAdapter<Message>()).create();
	}

	private static final class InterfaceAdapter<T> implements JsonSerializer<T>, JsonDeserializer<T> {
		public JsonElement serialize(T object, Type interfaceType, JsonSerializationContext context) {
			final JsonObject wrapper = new JsonObject();
			wrapper.addProperty("type", object.getClass().getName());
			wrapper.add("data", context.serialize(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 java.lang.reflect.Type actualType = typeForName(typeName);
			return context.deserialize(data, actualType);
		}

		private Class<?> 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;
		}
	}

	public String toJson() {
		return gson.toJson(this, Message.class) + "\n";
	}

	public static Message fromJson(String json) {
		return gson.fromJson(json, Message.class);
	}
}