PolymorphicTypeAdapter.java

/**
 * Copyright 2014 ArcBees Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package com.arcbees.vcs.util;

import java.lang.reflect.Type;

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.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

public class PolymorphicTypeAdapter<T> implements JsonSerializer<T>, JsonDeserializer<T> {
    private static final String CLASSNAME = "@class";
    private static final String VALUE = "@value";

    @Override
    public T deserialize(JsonElement json, Type type, JsonDeserializationContext context) throws JsonParseException {
        JsonObject jsonObject = json.getAsJsonObject();
        JsonPrimitive jsonPrimitive = (JsonPrimitive) jsonObject.get(CLASSNAME);
        String className = jsonPrimitive.getAsString();

        Class<?> clazz;
        try {
            clazz = Class.forName(className);
        } catch (ClassNotFoundException e) {
            throw new JsonParseException(e.getMessage());
        }

        return context.deserialize(jsonObject.get(VALUE), clazz);
    }

    @Override
    public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context) {
        JsonObject retValue = new JsonObject();

        String className = src.getClass().getCanonicalName();
        retValue.addProperty(CLASSNAME, className);

        JsonElement jsonElement = context.serialize(src);
        retValue.add(VALUE, jsonElement);

        return retValue;
    }
}