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Glassfish example source code file (UniqueIdGenerator.java)

This example Glassfish source code file (UniqueIdGenerator.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Glassfish tags/keywords

interruptedexception, interruptedexception, log, logger, logger, logging, uniqueidgenerator, uniqueidgenerator

The Glassfish UniqueIdGenerator.java source code

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 1997-2010 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package com.sun.ejb.codegen;

import java.util.logging.Logger;
import java.util.logging.Level;

import com.sun.ejb.containers.EjbContainerUtilImpl;
import com.sun.logging.LogDomains;


/**
 * Generates unique id for an application or stand alone ejb module.
 * 
 * It uses the low order 6 bytes of the system current time. The remaining
 * 2 bytes are reserved for the beans inside the application and stand 
 * alone ejb module.
 *
 * The unique id generated by this generator will eventually wrap after 
 * 2^48 milli-seconds (8,925.25 years).
 * 
 * The two bytes reserved for the beans in the application or stand alone ejb 
 * module will allow max 2^16 (65,536) beans.
 *
 * @author  Nazrul Islam
 * @since   JDK1.4
 */
public class UniqueIdGenerator {

    /** last unique id given out by this id generator */
    private long _lastUid                      = 0;

    /** the singleton instance */
    private static final UniqueIdGenerator _instance = new UniqueIdGenerator();


    private Logger _logger = LogDomains.getLogger(UniqueIdGenerator.class, LogDomains.EJB_LOGGER);

    private UniqueIdGenerator() { }

    /**
     * Returns the singleton instance of this class.
     *
     * @return    the singleton instance
     */
    public static UniqueIdGenerator getInstance() {
        return _instance;
    }

    /**
     * Returns the next unique id for an application or 
     * stand alone ejb module.
     *
     * @return    the next unique id
     */
    public long getNextUniqueId() {

        synchronized (this) {
            while (true) {
                long uid  = System.currentTimeMillis();

                // uses the low order 6 bytes as unique id;
                // remaining 2 bytes are reserved for the beans inside the app
                uid       = (uid << 16);

                // ensures that we have a unique id
                if (this._lastUid != uid) {
                    this._lastUid = uid;
                    break;
                } else {
                    try {
                        Thread.currentThread().sleep(1);
                    } catch (InterruptedException ie) {
                        // log debug msg here
						_logger.log(Level.WARNING,"Thread.sleep interrupted ",ie);
                    }
                }
            }
            return this._lastUid;
        }
    }
}

Other Glassfish examples (source code examples)

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