PeriodConverter.java

/*
 * GSON Joda Time Serialisers
 *
 * Copyright 2015-2017 Greg Kopff
 * All rights reserved.
 *
 * 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 com.fatboyindustrial.gsonjodatime;

import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

import org.joda.time.Period;
import org.joda.time.format.ISOPeriodFormat;
import org.joda.time.format.PeriodFormatter;

import java.lang.reflect.Type;

/**
 * GSON serialiser/deserialiser for converting Joda {@link Period} objects.
 */
public class PeriodConverter  implements JsonSerializer<Period>, JsonDeserializer<Period>
{
  /**
   * Gson invokes this call-back method during serialization when it encounters a field of the
   * specified type. <p>
   *
   * In the implementation of this call-back method, you should consider invoking
   * {@link JsonSerializationContext#serialize(Object, Type)} method to create JsonElements for any
   * non-trivial field of the {@code src} object. However, you should never invoke it on the
   * {@code src} object itself since that will cause an infinite loop (Gson will call your
   * call-back method again).
   * @param src the object that needs to be converted to Json.
   * @param typeOfSrc the actual type (fully genericized version) of the source object.
   * @return a JsonElement corresponding to the specified object.
   */
  @Override
  public JsonElement serialize(Period src, Type typeOfSrc, JsonSerializationContext context)
  {
    final PeriodFormatter fmt = ISOPeriodFormat.standard();
    return new JsonPrimitive(fmt.print(src));
  }

  /**
   * Gson invokes this call-back method during deserialization when it encounters a field of the
   * specified type. <p>
   *
   * In the implementation of this call-back method, you should consider invoking
   * {@link JsonDeserializationContext#deserialize(JsonElement, Type)} method to create objects
   * for any non-trivial field of the returned object. However, you should never invoke it on the
   * the same type passing {@code json} since that will cause an infinite loop (Gson will call your
   * call-back method again).
   * @param json The Json data being deserialized
   * @param typeOfT The type of the Object to deserialize to
   * @return a deserialized object of the specified type typeOfT which is a subclass of {@code T}
   * @throws JsonParseException if json is not in the expected format of {@code typeOfT}
   */
  @Override
  public Period deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
      throws JsonParseException
  {
    // Do not try to deserialize null or empty values
    if (json.getAsString() == null || json.getAsString().isEmpty())
    {
      return null;
    }
    final PeriodFormatter fmt = ISOPeriodFormat.standard();
    return fmt.parsePeriod(json.getAsString());
  }
}