keygenerator.java

Java的面向对象数据库系统的源代码

// You can redistribute this software and/or modify it under the terms of
// the Ozone Core License version 1 published by ozone-db.org.
//
// The original code and portions created by SMB are
// Copyright (C) 1997-@year@ by SMB GmbH. All rights reserved.
//
// $Id: KeyGenerator.java,v 1.5 2002/09/18 06:54:15 per_nyfelt Exp $

package org.ozoneDB.core;

import org.ozoneDB.Setup;
import org.ozoneDB.util.LogWriter;


/**
 * @author <a href="http://www.softwarebuero.de/">SMB</a>
 * @version $Revision: 1.5 $Date: 2002/09/18 06:54:15 $
 */
public final class KeyGenerator extends ServerComponent {

    private long		idCount = 0;

    private long		idBorder = -1;

    private long		idRange = 5000;


    public KeyGenerator( Env env ) {
        super( env );
    }


    public void startup() throws Exception {
        env.logWriter.newEntry( this, "startup...", LogWriter.INFO );
    }


    public void shutdown() throws Exception {
        env.logWriter.newEntry( this, "shutdown...", LogWriter.INFO );
    }


    public void save() throws Exception {
    }


    public long nextID() {
        return nextID( 1 );
    }


    public synchronized long nextID( long range ) {
        if (idCount + range >= idBorder) {
            try {
                idCount = env.state.longProperty( Setup.XOID, -1 );
                if (idCount == -1) {
                    throw new Exception( "Unable to access the " + Setup.XOID + " property." );
                }
                idBorder = idCount + range + idRange;

                env.state.setLongProperty( Setup.XOID, idBorder );
                setChanged();
            } catch (Exception e) {
                env.fatalError( /*null*/this, "nextID(): " + e.toString(), e );
            }
        }
        long result = idCount;
        idCount += range;

        return result;
    }

}