UUID的引见与使用

UUID的介绍与使用
/**?*//**
?????*?
?????*?@author?wangdei
?????*?在?http://www.bt285.cn?BT下载
?????*?http://www.5a520.cn?小说520?上使用.?
?????*
?????*/
????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());
????????????}
??????????}


????}

四:UUID在使用二
可以采用一个开源实现：http://jug.safehaus.org/ 或者用jakarta commons下的http://jakarta.apache.org/commons/sandbox/id/
五:UUID在使用三
在