JsonStringWrapperAdapterFactory.java

package com.devicehive.json.adapters;

/*
 * #%L
 * DeviceHive Common Dao Interfaces
 * %%
 * Copyright (C) 2016 DataArt
 * %%
 * 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.
 * #L%
 */


import com.devicehive.model.JsonStringWrapper;
import com.google.gson.*;
import com.google.gson.internal.Streams;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;

public class JsonStringWrapperAdapterFactory implements TypeAdapterFactory {

    @Override
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        if (!JsonStringWrapper.class.isAssignableFrom(type.getRawType())) {
            return null;
        }
        /**
         * Cast is checked since we check if JsonStringWrapper is assignable from type T
         */
        @SuppressWarnings("unchecked")
        TypeAdapter<T> result = (TypeAdapter<T>) new JsonStringWrapperAdapter();
        return result;
    }

    private static class JsonStringWrapperAdapter extends TypeAdapter<JsonStringWrapper> {


        @Override
        public void write(JsonWriter out, JsonStringWrapper value) throws IOException {
            if (value == null && out.getSerializeNulls()) {
                out.nullValue();
            } else if (value != null) {
                Streams.write(new JsonParser().parse(value.getJsonString()), out);
            }
        }

        @Override
        public JsonStringWrapper read(JsonReader in) throws IOException {
            JsonElement jsonElement = Streams.parse(in);
            return !JsonNull.INSTANCE.equals(jsonElement)
                    ? new JsonStringWrapper(jsonElement.toString())
                    : null;
        }
    }
}