com.ecwid.mailchimp.internal.gson.MailChimpGsonFactory.java Source code

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Here is the source code for com.ecwid.mailchimp.internal.gson.MailChimpGsonFactory.java

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/*
 * Copyright 2012 Ecwid, 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.ecwid.mailchimp.internal.gson;

import com.ecwid.mailchimp.MailChimpObject;
import com.google.gson.ExclusionStrategy;
import com.google.gson.FieldAttributes;
import com.google.gson.FieldNamingStrategy;
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.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

/**
 * Factory creating {@link Gson} objects to be used for MailChimp API calls wrapping.
 * 
 * @author Vasily Karyaev <v.karyaev@gmail.com>
 */
public class MailChimpGsonFactory {

    private MailChimpGsonFactory() {
    }

    /**
     * Excludes every field in any class.
     * Only instances of {@link MailChimpObject} can be serialized
     * (see {@link MailChimpObjectTypeAdapter}).
     */
    private static final ExclusionStrategy exclusionStrategy = new ExclusionStrategy() {
        @Override
        public boolean shouldSkipField(FieldAttributes fa) {
            return true;
        }

        @Override
        public boolean shouldSkipClass(Class<?> type) {
            return false;
        }
    };

    /**
     * Translates dates to json strings and vice versa.
     * <p>
     * This adapter is used instead of {@link GsonBuilder#setDateFormat(java.lang.String)}
     * due to gson's lack of ability to set proper time zone.
     */
    private static class DateTypeAdapter implements JsonSerializer<Date>, JsonDeserializer<Date> {
        private final DateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

        DateTypeAdapter() {
            format.setTimeZone(TimeZone.getTimeZone("UTC"));
        }

        @Override
        public JsonElement serialize(Date t, Type type, JsonSerializationContext jsc) {
            synchronized (format) {
                return new JsonPrimitive(format.format(t));
            }
        }

        @Override
        public Date deserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
                throws JsonParseException {
            synchronized (format) {
                try {
                    return !je.getAsString().isEmpty() ? format.parse(je.getAsString()) : null;
                } catch (ParseException e) {
                    throw new IllegalArgumentException("Cannot deserialize date: " + je);
                }
            }
        }
    }

    /**
     * Creates a new {@link Gson} object.
     */
    public static Gson createGson() {
        GsonBuilder builder = new GsonBuilder();
        builder.setExclusionStrategies(exclusionStrategy);
        builder.registerTypeAdapter(Date.class, new DateTypeAdapter());
        builder.registerTypeAdapterFactory(MailChimpObjectTypeAdapter.FACTORY);
        return builder.create();
    }
}