src/main/java/org/eclipse/openk/common/GsonUTCDateAdapter.java

/*
 *******************************************************************************
 * Copyright (c) 2018 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * SPDX-License-Identifier: EPL-2.0
 *******************************************************************************
*/

package org.eclipse.openk.common;

import com.google.gson.*;

import java.lang.reflect.Type;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

public class GsonUTCDateAdapter implements JsonSerializer<Date>, JsonDeserializer<Date> {

    private final DateFormat dateFormat;

    public GsonUTCDateAdapter() {
        dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);      //This is the format I need
        dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));                               //This is the key line which converts the date to UTC which cannot be accessed with the default serializer
    }

    @Override
    public synchronized JsonElement serialize(Date date, Type type, JsonSerializationContext jsonSerializationContext) {
        if( date != null ) {
            return new JsonPrimitive(dateFormat.format(date));
        }
        else {
            return null;
        }

    }

    @Override
    public synchronized Date deserialize(JsonElement jsonElement, Type type, JsonDeserializationContext jsonDeserializationContext) {
        try {
            String stringElem = jsonElement.getAsString();
            if( stringElem.isEmpty()) {
                return null;
            }
            else {
                return dateFormat.parse(stringElem);
            }
        } catch (ParseException e) {
            throw new JsonParseException(e);
        }
    }
}