co.aurasphere.botmill.fb.internal.util.json.JsonUtils.java Source code

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Here is the source code for co.aurasphere.botmill.fb.internal.util.json.JsonUtils.java

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/*
 * MIT License
 *
 * Copyright (c) 2016 BotMill.io
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package co.aurasphere.botmill.fb.internal.util.json;

import java.util.Calendar;
import java.util.List;

import co.aurasphere.botmill.fb.model.base.Attachment;
import co.aurasphere.botmill.fb.model.incoming.callback.IncomingMessage;
import co.aurasphere.botmill.fb.model.outcoming.template.button.Button;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

/**
 * Utility class for handling JSON serialization and deserialization.
 * 
 * @author Donato Rimenti
 */
public class JsonUtils {

    /**
     * Gson which handles the JSON conversion.
     */
    private static Gson gson;

    /**
     * Instantiates a new JsonUtils.
     */
    private JsonUtils() {
    }

    /**
     * Initializes the current Gson object if null and returns it. The Gson
     * object has custom adapters to manage datatypes according to Facebook
     * formats.
     * 
     * @return the current instance of Gson.
     */
    private static Gson getGson() {
        if (gson == null) {
            // Creates the Gson object which will manage the information
            // received
            GsonBuilder builder = new GsonBuilder();

            // Serializes enums as lower-case.
            builder.registerTypeHierarchyAdapter(Enum.class, new EnumLowercaseSerializer());

            // Serializes calendar in format YYYY-MM-DDThh:mm.
            builder.registerTypeHierarchyAdapter(Calendar.class, new CalendarSerializer());

            // Deserializes payloads from interface.
            builder.registerTypeAdapter(Attachment.class, new AttachmentDeserializer());

            // Deserializes buttons from interface.
            builder.registerTypeAdapter(Button.class, new ButtonDeserializer());

            builder.registerTypeAdapter(List.class, new PolimorphicalListSerializer<List<Button>>());

            // Deserializes incoming messages from interface.
            builder.registerTypeAdapter(IncomingMessage.class, new IncomingMessageDeserializer());

            gson = builder.create();
        }
        return gson;
    }

    /**
     * From json.
     *
     * @param <T>
     *            the generic type
     * @param json
     *            the string from which the object is to be deserialized.
     * @param T
     *            the type of the desired object.
     * @return an object of type T from the string. Returns null if json is
     *         null.
     * @see Gson#fromJson(String, Class)
     */
    public static <T> T fromJson(String json, Class<T> T) {
        return getGson().fromJson(json, T);
    }

    /**
     * To json.
     *
     * @param src
     *            the object for which Json representation is to be created
     *            setting for Gson .
     * @return Json representation of src.
     * @see Gson#toJson(Object)
     */
    public static String toJson(Object src) {
        return getGson().toJson(src);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "JsonUtils []";
    }

}