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[轉(zhuǎn)]怎樣用java生成GUID與UUID

地址：http://kong-bai.javaeye.com/blog/375578

GUID是一個128位長的數(shù)字，一般用16進(jìn)制表示。算法的核心思想是結(jié)合機(jī)器的網(wǎng)卡、當(dāng)?shù)貢r間、一個隨機(jī)數(shù)來生成GUID。從理論上講，如果一臺機(jī)器每秒產(chǎn)生10000000個GUID，則可以保證（概率意義上）3240年不重復(fù)。

UUID是1.5中新增的一個類，在java.util下，用它可以產(chǎn)生一個號稱全球唯一的ID
Java代碼：

import java.util.UUID;

public class Test {

public static void main(String[] args) {

UUID uuid = UUID.randomUUID();

System.out.println (uuid);

}

編譯運行輸出：
07ca3dec-b674-41d0-af9e-9c37583b08bb

兩種方式生成guid 與uuid

需要comm log 庫
Java代碼：

/**

* @author Administrator

*

* TODO To change the template for this generated type comment go to

* Window - Preferences - Java - Code Style - Code Templates

*/

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);

}

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);

}

/*

* 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());

}

同樣

Java代碼：

UUID uuid = UUID.randomUUID();

System.out.println("{"+uuid.toString()+"}");

UUID是指在一臺機(jī)器上生成的數(shù)字，它保證對在同一時空中的所有機(jī)器都是唯一的。通常平臺會提供生成UUID的API。UUID按照開放軟件基金會(OSF)制定的標(biāo)準(zhǔn)計算，用到了以太網(wǎng)卡地址、納秒級時間、芯片ID碼和許多可能的數(shù)字。由以下幾部分的組合：當(dāng)前日期和時間(UUID的第一個部分與時間有關(guān)，如果你在生成一個UUID之后，過幾秒又生成一個UUID，則第一個部分不同，其余相同)，時鐘序列，全局唯一的IEEE機(jī)器識別號（如果有網(wǎng)卡，從網(wǎng)卡獲得，沒有網(wǎng)卡以其他方式獲得），UUID的唯一缺陷在于生成的結(jié)果串會比較長。關(guān)于UUID這個標(biāo)準(zhǔn)使用最普遍的是微軟的GUID(Globals Unique Identifiers)。

posted on 2010-12-01 23:54 WangShishuai 閱讀(689) 評論(0) 編輯收藏所屬分類: Java

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