v7cr.v7db.Versioning.java Source code

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Here is the source code for v7cr.v7db.Versioning.java

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/**
 * Copyright (c) 2011, Thilo Planz. All rights reserved.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package v7cr.v7db;

import java.util.ConcurrentModificationException;

import org.bson.BSONObject;

import com.mongodb.BasicDBObject;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.WriteResult;

public class Versioning {

    /**
     * The field name for the version number
     */
    public static final String VERSION = "_version";

    /**
     * inserts a first version of an object.
     * 
     * It must not already have a _version field. _version will be set to 1.
     * 
     */
    public static WriteResult insert(DBCollection collection, DBObject object) {
        if (object.containsField(VERSION)) {
            throw new IllegalArgumentException("The object already has a _version " + object);
        }
        object.put(VERSION, 1);
        return collection.insert(object);
    }

    /**
     * updates an object, but only if the base version has not been changed in
     * the meantime. The object must have an _id field. The _version field if
     * present is ignored, and set to baseVersion+1.
     */

    public static WriteResult update(DBCollection collection, final int baseVersion, DBObject object) {
        object.put(VERSION, baseVersion + 1);
        Object id = object.get("_id");
        WriteResult result = collection.update(new BasicDBObject("_id", id).append(VERSION, baseVersion), object);
        if (result.getN() != 1)
            throw new ConcurrentModificationException("baseVersion has changed");
        return result;
    }

    public static Integer getVersion(BSONBackedObject b) {
        return b.getIntegerField(VERSION);
    }

    public static Integer getVersion(BSONObject b) {
        return (Integer) b.get(VERSION);
    }
}