Mega Code Archive
A 32 byte GUID generator
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/*************************************************************************
* *
* 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();
}
}
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