com.goodow.realtime.server.model.DeltaSerializer.java Source code

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Here is the source code for com.goodow.realtime.server.model.DeltaSerializer.java

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/*
 * Copyright 2012 Goodow.com
 * 
 * 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.goodow.realtime.server.model;

import com.google.common.base.Preconditions;
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 java.util.logging.Logger;

public class DeltaSerializer {

    @SuppressWarnings("unused")
    private static final Logger log = Logger.getLogger(DeltaSerializer.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 JsonElement dataToClientJson(Delta<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: Consider using Delta<JSONObject> instead.
        // The reason I haven't done it yet is because it's not immutable,
        // and also for reasons described in Delta.
        JsonElement payloadJson;
        try {
            payloadJson = new JsonParser().parse(data.getPayload());
        } catch (JsonParseException e) {
            throw new IllegalArgumentException("Invalid payload for " + data, e);
        }

        JsonArray json = new JsonArray();
        try {
            Preconditions.checkArgument(resultingRevision >= 0, "invalid rev %s", resultingRevision);
            json.add(new JsonPrimitive(resultingRevision));
            long sanityCheck = json.get(0).getAsLong();
            if (sanityCheck != resultingRevision) {
                throw new AssertionError("resultingRevision " + resultingRevision
                        + " not losslessly represented in JSON, got back " + sanityCheck);
            }
            json.add(new JsonPrimitive(data.getSession().userId));
            json.add(new JsonPrimitive(data.getSession().sessionId));
            json.add(payloadJson);
            return json;
        } catch (JsonParseException e) {
            throw new Error(e);
        }
    }

    private DeltaSerializer() {
    }
}