UUID的介绍与使用

*

*@authorwangdei

*在http://www.bt285.cnBT下载

*http://www.5a520.cn小说520上使用.

*

*/

publicclassRandomGUIDextendsObject{

protectedfinalorg.apache.commons.logging.Loglogger=org.apache.commons.logging.LogFactory

.getLog(getClass());

publicStringvalueBeforeMD5="";

publicStringvalueAfterMD5="";

privatestaticRandommyRand;

privatestaticSecureRandommySecureRand;

privatestaticStrings_id;

privatestaticfinalintPAD_BELOW=0x10;

privatestaticfinalintTWO_BYTES=0xFF;

/**//*

*StaticblocktotakecareofonetimesecureRandomseed.

*IttakesafewsecondstoinitializeSecureRandom.Youmight

*wanttoconsiderremovingthisstaticblockorreplacing

*itwitha"timesincefirstloaded"seedtoreducethistime.

*ThisblockwillrunonlyonceperJVMinstance.

*/

static{

mySecureRand=newSecureRandom();

longsecureInitializer=mySecureRand.nextLong();

myRand=newRandom(secureInitializer);

try{

s_id=InetAddress.getLocalHost().toString();

}catch(UnknownHostExceptione){

e.printStackTrace();

}

}

/**//*

*Defaultconstructor.Withnospecificationofsecurityoption,

*thisconstructordefaultstolowersecurity,highperformance.

*/

publicRandomGUID(){

getRandomGUID(false);

}

/**//*

*Constructorwithsecurityoption.Settingsecuretrue

*enableseachrandomnumbergeneratedtobecryptographically

*strong.SecurefalsedefaultstothestandardRandomfunctionseeded

*withasinglecryptographicallystrongrandomnumber.

*/

publicRandomGUID(booleansecure){

getRandomGUID(secure);

}

/**//*

*MethodtogeneratetherandomGUID

*/

privatevoidgetRandomGUID(booleansecure){

MessageDigestmd5=null;

StringBuffersbValueBeforeMD5=newStringBuffer(128);

try{

md5=MessageDigest.getInstance("MD5");

}catch(NoSuchAlgorithmExceptione){

logger.error("Error:"+e);

}

try{

longtime=System.currentTimeMillis();

longrand=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();

StringBuffersb=newStringBuffer(32);

for(intj=0;j<array.length;++j){

intb=array[j]&TWO_BYTES;

if(b<PAD_BELOW)

sb.append('0');

sb.append(Integer.toHexString(b));

}

valueAfterMD5=sb.toString();

}catch(Exceptione){

logger.error("Error:"+e);

}

}

/**//*

*ConverttothestandardformatforGUID

*(UsefulforSQLServerUniqueIdentifiers,etc.)

*Example:C2FEEEAC-CFCD-11D1-8B05-00600806D9B6

*/

publicStringtoString(){

Stringraw=valueAfterMD5.toUpperCase();

StringBuffersb=newStringBuffer(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));

returnsb.toString();

}

//Demonstratonandselftestofclass

publicstaticvoidmain(Stringargs[]){

for(inti=0;i<100;i++){

RandomGUIDmyGUID=newRandomGUID();

System.out.println("SeedingString="+myGUID.valueBeforeMD5);

System.out.println("rawGUid="+myGUID.valueAfterMD5);

System.out.println("RandomGUid="+myGUID.toString());

}

}