Java tutorial
/************************************************************************* * * * EJBCA: The OpenSource Certificate Authority * * * * This software 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 any later version. * * * * See terms of license at gnu.org. * * * *************************************************************************/ /** Shamelessly ripped from generated XDoclet source, because I don't want to generate util classes. * * @author XDoclet.sf.net * @version $Id: GUIDGenerator.java 5585 2008-05-01 20:55:00Z anatom $ */ public class GUIDGenerator { /** Cached per JVM server IP. */ private static String hexServerIP = null; // initialise the secure random instance private static final java.security.SecureRandom seeder = new java.security.SecureRandom(); /** * A 32 byte GUID generator (Globally Unique ID). These artificial keys SHOULD <strong>NOT </strong> be seen by the user, * not even touched by the DBA but with very rare exceptions, just manipulated by the database and the programs. * * Usage: Add an id field (type java.lang.String) to your EJB, and add setId(XXXUtil.generateGUID(this)); to the ejbCreate method. */ public static final String generateGUID(Object o) { StringBuffer tmpBuffer = new StringBuffer(16); if (hexServerIP == null) { java.net.InetAddress localInetAddress = null; try { localInetAddress = java.net.InetAddress.getLocalHost(); } catch (java.net.UnknownHostException 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(); } }