com.google.walkaround.slob.server.ChangeDataSerializer.java Source code

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Here is the source code for com.google.walkaround.slob.server.ChangeDataSerializer.java

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/*
 * 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.common.base.Preconditions;
import com.google.walkaround.slob.shared.ChangeData;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.logging.Logger;

/**
 * @author danilatos@google.com (Daniel Danilatos)
 */
public class ChangeDataSerializer {

    private ChangeDataSerializer() {
    }

    @SuppressWarnings("unused")
    private static final Logger log = Logger.getLogger(ChangeDataSerializer.class.getName());

    /** The largest integer that can be represented losslessly by a double */
    public static final long MAX_DOUBLE_INTEGER = 1L << 52 - 1;

    public static JSONObject dataToClientJson(ChangeData<String> data, long resultingRevision) {
        Preconditions.checkArgument(resultingRevision <= MAX_DOUBLE_INTEGER, "Resulting revision %s is too large",
                resultingRevision);

        // Assume payload is JSON, and parse it to avoid nested json.
        // TODO(danilatos): Consider using ChangeData<JSONObject> instead.
        // The reason I haven't done it yet is because it's not immutable,
        // and also for reasons described in ChangeData.
        JSONObject payloadJson;
        try {
            payloadJson = new JSONObject(data.getPayload());
        } catch (JSONException e) {
            throw new IllegalArgumentException("Invalid payload for " + data, e);
        }

        JSONObject json = new JSONObject();
        try {
            Preconditions.checkArgument(resultingRevision >= 0, "invalid rev %s", resultingRevision);
            json.put("revision", resultingRevision);
            long sanityCheck = json.getLong("revision");
            if (sanityCheck != resultingRevision) {
                throw new AssertionError("resultingRevision " + resultingRevision
                        + " not losslessly represented in JSON, got back " + sanityCheck);
            }
            json.put("sid", data.getClientId().getId());
            json.put("op", payloadJson);
            return json;
        } catch (JSONException e) {
            throw new Error(e);
        }
    }

}