/*
* Copyright 2011 Google Inc. All Rights Reserved.
*
* 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.google.walkaround.slob.server;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
import com.google.walkaround.slob.shared.MessageException;
import org.waveprotocol.wave.communication.gson.GsonException;
import org.waveprotocol.wave.communication.gson.GsonSerializable;
import org.waveprotocol.wave.communication.json.RawStringData;
/**
* Utilities for JSON protobuf handling based on GSON.
*
* @author piotrkaleta@google.com (Piotr Kaleta)
* @author ohler@google.com (Christian Ohler)
*/
public class GsonProto {
private GsonProto() {}
public enum JsonStrategy {
REGULAR, MULTISTAGE,
}
public static <T extends GsonSerializable> T fromGson(T gsonObj, String serialized)
throws MessageException {
Gson gson = new Gson();
JsonElement jsonElement = new JsonParser().parse(serialized);
try {
gsonObj.fromGson(jsonElement, gson, null);
return gsonObj;
} catch (RuntimeException e) {
// I've seen IllegalStateExceptions in JsonArray.getAsString().
throw new MessageException("Failed to parse " + gsonObj.getClass() + ": " + serialized, e);
} catch (GsonException e) {
throw new MessageException("Failed to parse " + gsonObj.getClass() + ": " + serialized, e);
}
}
public static String toJson(GsonSerializable message, JsonStrategy strategy) {
Gson gson = new Gson();
// TODO(piotrkaleta): Do we need multistage strategy at all?
switch (strategy) {
case REGULAR:
return gson.toJson(message.toGson(null, gson));
case MULTISTAGE:
RawStringData data = new RawStringData();
JsonElement rootElement = message.toGson(data, gson);
data.setBaseStringIndex(data.addString(gson.toJson(rootElement)));
return data.serialize();
default:
throw new AssertionError("Unknown JsonStrategy: " + strategy);
}
}
/**
* Helper method to turn Gson object into JSON representation
*
* @return String containing JSON representation of an object
*/
public static String toJson(GsonSerializable message) {
return toJson(message, JsonStrategy.REGULAR);
}
}