java生成GUID与UUID
2012-04-18 15:42
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两种方式生成guid 与uuid
同样
UUID uuid = UUID.randomUUID();
System.out.println("{"+uuid.toString()+"}");
UUID是指在一台机器上生成的数字,它保证对在同一时空中的所有机器都是唯一的。通常平台会提供生成UUID的API。UUID按照开放软件基金会(OSF)制定的标准计算,用到了以太网卡地址、纳秒级时间、芯片ID码和许多可能的数字。由以下几部分的组合:当前日期和时间(UUID的第一个部分与时间有关,如果你在生成一个UUID之后,过几秒又生成一个UUID,则第一个部分不同,其余相同),时钟序列,全局唯一的IEEE机器识别号(如果有网卡,从网卡获得,没有网卡以其他方式获得),UUID的唯一缺陷在于生成的结果串会比较长。关于UUID这个标准使用最普遍的是微软的GUID(Globals
Unique Identifiers)。
转自http://blog.csdn.net/xiajing12345/article/details/358976
import java.net.InetAddress; import java.net.UnknownHostException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.util.Random; public class RandomGUID extends Object { // protected final org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory // .getLog(getClass()); public String valueBeforeMD5 = ""; public String valueAfterMD5 = ""; private static Random myRand; private static SecureRandom mySecureRand; private static String s_id; private static final int PAD_BELOW = 0x10; private static final int TWO_BYTES = 0xFF; /* * Static block to take care of one time secureRandom seed. It takes a few * seconds to initialize SecureRandom. You might want to consider removing * this static block or replacing it with a "time since first loaded" seed * to reduce this time. This block will run only once per JVM instance. */ static { mySecureRand = new SecureRandom(); long secureInitializer = mySecureRand.nextLong(); myRand = new Random(secureInitializer); try { s_id = InetAddress.getLocalHost().toString(); } catch (UnknownHostException e) { e.printStackTrace(); } } /* * Default constructor. With no specification of security option, this * constructor defaults to lower security, high performance. */ public RandomGUID() { getRandomGUID(false); } /* * Constructor with security option. Setting secure true enables each random * number generated to be cryptographically strong. Secure false defaults to * the standard Random function seeded with a single cryptographically * strong random number. */ public RandomGUID(boolean secure) { getRandomGUID(secure); } /* * Method to generate the random GUID */ private void getRandomGUID(boolean secure) { MessageDigest md5 = null; StringBuffer sbValueBeforeMD5 = new StringBuffer(128); try { md5 = MessageDigest.getInstance("MD5"); } catch (NoSuchAlgorithmException e) { // logger.error("Error: " + e); System.out.println(e); } try { long time = System.currentTimeMillis(); long rand = 0; if (secure) { rand = mySecureRand.nextLong(); } else { rand = myRand.nextLong(); } sbValueBeforeMD5.append(s_id); sbValueBeforeMD5.append(":"); sbValueBeforeMD5.append(Long.toString(time)); sbValueBeforeMD5.append(":"); sbValueBeforeMD5.append(Long.toString(rand)); valueBeforeMD5 = sbValueBeforeMD5.toString(); md5.update(valueBeforeMD5.getBytes()); byte[] array = md5.digest(); StringBuffer sb = new StringBuffer(32); for (int j = 0; j < array.length; ++j) { int b = array[j] & TWO_BYTES; if (b < PAD_BELOW) sb.append('0'); sb.append(Integer.toHexString(b)); } valueAfterMD5 = sb.toString(); } catch (Exception e) { // logger.error("Error:" + e); System.out.println(e); } } /* * Convert to the standard format for GUID (Useful for SQL Server * UniqueIdentifiers, etc.) Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6 */ public String toString() { String raw = valueAfterMD5.toUpperCase(); StringBuffer sb = new StringBuffer(64); sb.append(raw.substring(0, 8)); sb.append("-"); sb.append(raw.substring(8, 12)); sb.append("-"); sb.append(raw.substring(12, 16)); sb.append("-"); sb.append(raw.substring(16, 20)); sb.append("-"); sb.append(raw.substring(20)); return sb.toString(); } // Demonstraton and self test of class public static void main(String args[]) { for (int i = 0; i < 100; i++) { RandomGUID myGUID = new RandomGUID(); System.out.println("Seeding String=" + myGUID.valueBeforeMD5); System.out.println("rawGUID=" + myGUID.valueAfterMD5); System.out.println("RandomGUID=" + myGUID.toString()); } } }
同样
UUID uuid = UUID.randomUUID();
System.out.println("{"+uuid.toString()+"}");
UUID是指在一台机器上生成的数字,它保证对在同一时空中的所有机器都是唯一的。通常平台会提供生成UUID的API。UUID按照开放软件基金会(OSF)制定的标准计算,用到了以太网卡地址、纳秒级时间、芯片ID码和许多可能的数字。由以下几部分的组合:当前日期和时间(UUID的第一个部分与时间有关,如果你在生成一个UUID之后,过几秒又生成一个UUID,则第一个部分不同,其余相同),时钟序列,全局唯一的IEEE机器识别号(如果有网卡,从网卡获得,没有网卡以其他方式获得),UUID的唯一缺陷在于生成的结果串会比较长。关于UUID这个标准使用最普遍的是微软的GUID(Globals
Unique Identifiers)。
转自http://blog.csdn.net/xiajing12345/article/details/358976
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