IdentifierUtil.java

/*
 * Copyright (C) 2009 eXo Platform SAS.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */
package org.exoplatform.commons.utils;

import org.exoplatform.services.log.ExoLogger;
import org.exoplatform.services.log.Log;

import java.net.InetAddress;
import java.security.SecureRandom;

/**
 * Jul 19, 2004
 * 
 * @author: Tuan Nguyen
 * @version: $Id: IdentifierUtil.java,v 1.1 2004/07/20 12:22:42 tuan08 Exp $
 */
public class IdentifierUtil
{

   /**
    * The logger
    */
   private static final Log LOG = ExoLogger.getLogger("exo.kernel.commons.IdentifierUtil");

   private static String hexServerIP_ = null;

   private static final SecureRandom seeder_ = new SecureRandom();

   //============================================================================
   // ==
   static public String generateUUID(Object o)
   {
      StringBuffer tmpBuffer = new StringBuffer(16);
      if (hexServerIP_ == null)
      {
         InetAddress localInetAddress = null;
         try
         {
            // get the inet address
            localInetAddress = InetAddress.getLocalHost();
         }
         catch (java.net.UnknownHostException uhe)
         {
            // System .err .println(
            // "ContentSetUtil: Could not get the local IP address using InetAddress.getLocalHost()!"
            // );
            // todo: find better way to get around this...
            LOG.error(uhe.getLocalizedMessage(), uhe);
            return null;
         }
         byte serverIP[] = localInetAddress.getAddress();
         hexServerIP_ = hexFormat(getInt(serverIP), 8);
      }
      String hashcode = hexFormat(System.identityHashCode(o), 8);
      tmpBuffer.append(hexServerIP_);
      tmpBuffer.append(hashcode);

      long timeNow = System.currentTimeMillis();
      int timeLow = (int)timeNow & 0xFFFFFFFF;
      int node = seeder_.nextInt();

      StringBuffer guid = new StringBuffer(32);
      guid.append(hexFormat(timeLow, 8));
      guid.append(tmpBuffer.toString());
      guid.append(hexFormat(node, 8));
      return guid.toString();
   }

   private static int getInt(byte bytes[])
   {
      int i = 0;
      int j = 24;
      for (int k = 0; j >= 0; k++)
      {
         int l = bytes[k] & 0xff;
         i += l << j;
         j -= 8;
      }
      return i;
   }

   private static String hexFormat(int i, int j)
   {
      String s = Integer.toHexString(i);
      return padHex(s, j) + s;
   }

   private static String padHex(String s, int i)
   {
      StringBuffer tmpBuffer = new StringBuffer();
      if (s.length() < i)
      {
         for (int j = 0; j < i - s.length(); j++)
         {
            tmpBuffer.append('0');
         }
      }
      return tmpBuffer.toString();
   }
}