Mega Code Archive
Generates a UUID
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/**************************************************************************************
* Copyright (c) Jonas BonŽr, Alexandre Vasseur. All rights reserved. *
* http://aspectwerkz.codehaus.org *
* ---------------------------------------------------------------------------------- *
* The software in this package is published under the terms of the LGPL license *
* a copy of which has been included with this distribution in the license.txt file. *
**************************************************************************************/
import java.net.InetAddress;
import java.security.SecureRandom;
/**
* Generates a UUID. <p/>A Universally Unique Identifier (UUID) is a 128 bit number generated according to an algorithm
* that is garanteed to be unique in time A space from all other UUIDs.
*
* @author <a href="mailto:jboner@codehaus.org">Jonas BonŽr </a>
*/
public class UuidGenerator {
/**
* Random seeder.
*/
private static SecureRandom s_seeder = null;
/**
* Mid value, needed for calculation.
*/
private static String s_midValue = null;
/**
* Defines if the generator is initialized or not.
*/
private static boolean s_initialized = false;
/**
* Private constructor to prevent subclassing
*/
private UuidGenerator() {
}
/**
* Returns a unique uuid.
*
* @param obj the calling object (this)
* @return a unique uuid
*/
public static String generate(Object obj) {
if (!s_initialized) {
initialize(obj);
}
long timeNow = System.currentTimeMillis();
// get int value as unsigned
int timeLow = (int) timeNow & 0xFFFFFFFF;
int node = s_seeder.nextInt();
return (hexFormat(timeLow, 8) + s_midValue + hexFormat(node, 8));
}
/**
* Initializes the factory.
*
* @param obj
*/
private synchronized static void initialize(final Object obj) {
try {
InetAddress inet = InetAddress.getLocalHost();
byte[] bytes = inet.getAddress();
String hexInetAddress = hexFormat(getInt(bytes), 8);
String thisHashCode = hexFormat(System.identityHashCode(obj), 8);
s_midValue = hexInetAddress + thisHashCode;
s_seeder = new SecureRandom();
s_seeder.nextInt();
} catch (java.net.UnknownHostException e) {
throw new Error("can not initialize the UuidGenerator generator");
}
s_initialized = true;
}
/**
* Utility method.
*
* @param abyte
* @return
*/
private static int getInt(final byte[] abyte) {
int i = 0;
int j = 24;
for (int k = 0; j >= 0; k++) {
int l = abyte[k] & 0xff;
i += (l << j);
j -= 8;
}
return i;
}
/**
* Utility method.
*
* @param i
* @param j
* @return
*/
private static String hexFormat(final int i, final int j) {
String s = Integer.toHexString(i);
return padHex(s, j) + s;
}
/**
* Utility method.
*
* @param str
* @param i
* @return
*/
private static String padHex(final String str, final int i) {
StringBuffer buf = new StringBuffer();
if (str.length() < i) {
for (int j = 0; j < (i - str.length()); j++) {
buf.append('0');
}
}
return buf.toString();
}
}
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