org.waveprotocol.wave.communication.gson.GsonUtil.java Source code

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Here is the source code for org.waveprotocol.wave.communication.gson.GsonUtil.java

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.waveprotocol.wave.communication.gson;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonParser;
import com.google.gson.JsonPrimitive;

import org.waveprotocol.wave.communication.json.JsonLongHelper;
import org.waveprotocol.wave.communication.json.RawStringData;

/**
 * Utilities for working with GsonSerializable objects
 *
 */
public class GsonUtil {

    /**
     * A wrapper routine used to catch exceptions thrown while parsing and convert
     * them to GsonExceptions
     *
     * @param <T> A GsonSerializable object class
     * @param obj The object
     * @param json The root of a tree of JsonElements
     * @param gson The gson object used to parse multi-stage json
     * @param data The raw data object that contains the substring
     * @return The provided object
     * @throws GsonException
     */
    public static <T extends GsonSerializable> T parseGson(T obj, JsonElement json, Gson gson, RawStringData data)
            throws GsonException {
        try {
            obj.fromGson(json, gson, data);
            return obj;
        } catch (IllegalArgumentException e) {
            throw new GsonException("Unable to parse JSON", e);
        } catch (IllegalStateException e) {
            throw new GsonException("Unable to parse JSON", e);
        } catch (UnsupportedOperationException e) {
            throw new GsonException("Unable to parse JSON", e);
        }
    }

    /**
     * A wrapper routine used to catch exceptions thrown while parsing and convert
     * them to GsonExceptions
     *
     * @param <T> The type to deserialize
     * @param gson A Gson context
     * @param json The json string to interpret
     * @throws GsonException
     */
    public static <T extends GsonSerializable> void parseJson(T object, Gson gson, String json, RawStringData data)
            throws GsonException {
        try {
            JsonElement root = new JsonParser().parse(json);
            object.fromGson(root, gson, data);
        } catch (JsonParseException e) {
            throw new GsonException("Unable to parse Json", e);
        }
    }

    /**
     * A wrapper routine used to catch exceptions thrown while parsing and convert
     * them to GsonExceptions
     *
     * @param <T> The type to deserialize
     * @param gson A Gson context
     * @param json The json string to interpret
     * @param clazz The class object representing T
     * @return An instance representing the parsed json
     * @throws GsonException
     */
    public static <T> T parseJson(Gson gson, String json, Class<T> clazz) throws GsonException {
        try {
            return gson.fromJson(json, clazz);
        } catch (JsonParseException e) {
            throw new GsonException("Unable to parse Json", e);
        }
    }

    /**
     * Unpack a JsonElement into the object type
     *
     * @param <T> The type to deserialize
     * @param object The object used to accept the pare result
     * @param valueObj The root of a tree of JsonElements or an indirection index
     * @param gson A Gson context
     * @param raw
     * @throws GsonException
     */
    public static <T extends GsonSerializable> void extractJsonObject(T object, JsonElement valueObj, Gson gson,
            RawStringData raw) throws GsonException {
        if (valueObj.isJsonObject()) {
            object.fromGson(valueObj.getAsJsonObject(), gson, raw);
        } else if (valueObj.isJsonPrimitive()) {
            JsonPrimitive primitive = valueObj.getAsJsonPrimitive();
            String s = null;
            if (raw == null || !primitive.isString()) {
                throw new GsonException("Decoding " + valueObj + " as object " + object.getClass()
                        + " with no RawStringData given");
            }
            s = raw.getString(valueObj.getAsString());
            GsonUtil.parseJson(object, gson, s, raw);
        } else {
            throw new GsonException(
                    "Cannot decode valueObject " + valueObj.getClass() + " as object " + object.getClass());
        }
    }

    /**
     * Faithfully serializes a 64-bit long value as a two-number array.
     */
    public static JsonArray toJson(long value) {
        JsonArray arr = new JsonArray();
        arr.add(new JsonPrimitive(JsonLongHelper.getLowWord(value)));
        arr.add(new JsonPrimitive(JsonLongHelper.getHighWord(value)));
        return arr;
    }

    /**
     * Deserializes a two-number array from {@link #toJson(long)} into a long.
     */
    public static long fromJson(JsonElement e) {
        JsonArray arr = e.getAsJsonArray();
        return JsonLongHelper.toLong(arr.get(1).getAsInt(), arr.get(0).getAsInt());
    }

    private GsonUtil() {
    }
}