Java生成UUID

UUID(Universally Unique Identifier)全局唯一标识符,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。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。

在Java中生成UUID主要有以下几种方式:

1. JDK1.5
如果使用的JDK1.5的话,那么生成UUID变成了一件简单的事,以为JDK实现了UUID: java.util.UUID,直接调用即可.

UUID uuid = UUID.randomUUID();

2. 第三方开源类库(推荐使用):
最著名的是 JUG .特点上是: 纯Java实现，开源，LGPL协议。采用了Native的方式产生真正的Uuid.而且提供了不同平台的实现,包括:

Linux / x86
Windows (98, ME, NT, 2K, XP?) / x86
Solaris / Sparc
Mac OS X
FreeBSD / x86

import org.doomdark.uuid.UUID;

import org.doomdark.uuid.UUIDGenerator;

UUIDGenerator generator = UUIDGenerator.getInstance();

UUID uuid = generator.generateRandomBasedUUID();

3. Java代码实现:
如果你使用JDK1.4或以前版本,又不想加入第三方的类库的话,下面提供了一个纯Java的UUID实现. 不过需要注意的是:这里产生的可能不是真正的UUID，只不过重复的机会少一些而已。

import java.net.InetAddress;

import java.net.UnknownHostException;

/**

* UUID（Univeral Unique Identity）类

* Title: 生成唯一编码
*

* Description: 源自于w3c.org <

http://源自于w3c.org >

* Copyright: Copyright (c) 2001-2004
*

* @version 1.0

public final class UUID {

/**

* @serial Integer that helps create a unique UID.

private int unique;

/**

* @serial Long used to record the time. The time will be

* used to create a unique UID.

private long time;

/**

* InetAddress to make the UID globally unique

private static String address;

/**

* a random number

private static int hostUnique;

/**

* Used for synchronization

private static Object mutex;

private static long lastTime;

private static long DELAY;

private static String generateNoNetworkID() {

Thread current = Thread.currentThread();

String nid = current.activeCount() + System.getProperty( " os.version " )

+ System.getProperty( " user.name " )

+ System.getProperty( " java.version " );

System.out.println( " netWorkId = " + nid);

MD5 md5 = new MD5(nid);

md5.processString();

return md5.getStringDigest();

}

static {

hostUnique = ( new Object()).hashCode();

mutex = new Object();

lastTime = System.currentTimeMillis();

DELAY = 10 ; // in milliseconds

try {

String s = InetAddress.getLocalHost().getHostAddress();

MD5 md5 = new MD5(s);

md5.processString();

address = md5.getStringDigest();

} catch (UnknownHostException ex) {

address = generateNoNetworkID();

}

public UUID() {

synchronized (mutex) {

boolean done = false ;

while ( ! done) {

time = System.currentTimeMillis();

if (time lastTime + DELAY) {

// pause for a second to wait for time to change

try {

Thread.currentThread().sleep(DELAY);

} catch (java.lang.InterruptedException e) {

} // ignore exception

continue ;

} else {

lastTime = time;

done = true ;

}

unique = hostUnique;

}

public String toString() {

return Integer.toString(unique, 16 ) + Long.toString(time, 16 ) + address;

}

public boolean equals(Object obj) {

if ((obj != null ) && (obj instanceof UUID)) {

UUID uuid = (UUID) obj;

return (unique == uuid.unique && time == uuid.time && address

.equals(uuid.address));

} else {

return false ;

}

public static void main(String args[]) {

System.out.println( new UUID());

long start = System.currentTimeMillis();

System.out.println( new UUID());

long end = System.currentTimeMillis();

System.out.println((end - start));

System.out.println( new UUID().toString().length());

}

/**

* 返回最新的UUID号码

* @return String UUID，长50位

public final static String getUUID() {

UUID uid = new UUID();

return uid.toString();

}

其中使用到MD5加密算法,实现代码如下:

import java.io.ByteArrayInputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.UnsupportedEncodingException;

/**

* MD5 加密算法类

* Description: 源自于w3c.org <

http://源自于w3c.org >

* Copyright: Copyright (c) 2001-2004
*

* @version 1.0

public class MD5 {

private static final int BUFFER_SIZE = 1024 ;

private static final int S11 = 7 ;

private static final int S12 = 12 ;

private static final int S13 = 17 ;

private static final int S14 = 22 ;

private static final int S21 = 5 ;

private static final int S22 = 9 ;

private static final int S23 = 14 ;

private static final int S24 = 20 ;

private static final int S31 = 4 ;

private static final int S32 = 11 ;

private static final int S33 = 16 ;

private static final int S34 = 23 ;

private static final int S41 = 6 ;

private static final int S42 = 10 ;

private static final int S43 = 15 ;

private static final int S44 = 21 ;

private static byte padding[] = { ( byte ) 0x80 , ( byte ) 0 , ( byte ) 0 ,

( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 ,

( byte ) 0 } ;

private InputStream in = null ;

private boolean stringp = false ;

private int state[] = null ;

private long count = 0 ;

private byte buffer[] = null ;

private byte digest[] = null ;

private static String stringify( byte buf[]) {

StringBuffer sb = new StringBuffer( 2 * buf.length);

for ( int i = 0 ; i buf.length; i ++ ) {

int h = (buf[i] & 0xf0 ) >> 4 ;

int l = (buf[i] & 0x0f );

sb.append( new Character(( char ) ((h > 9 ) ? ' a ' + h - 10 : ' 0 ' + h)));

sb.append( new Character(( char ) ((l > 9 ) ? ' a ' + l - 10 : ' 0 ' + l)));

}

return sb.toString();

}

private final int F( int x, int y, int z) {

return ((x & y) | (( ~ x) & z));

}

private final int G( int x, int y, int z) {

return ((x & z) | (y & ( ~ z)));

}

private final int H( int x, int y, int z) {

return (x ^ y ^ z);

}

private final int I( int x, int y, int z) {

return (y ^ (x | ( ~ z)));

}

private final int rotate_left( int x, int n) {

return ((x << n) | (x >>> (32 - n)));

}

private final int FF( int a, int b, int c, int d, int x, int s, int ac) {

a += (F(b, c, d) + x + ac);

a = rotate_left(a, s);

a += b;

return a;

}

private final int GG( int a, int b, int c, int d, int x, int s, int ac) {

a += (G(b, c, d) + x + ac);

a = rotate_left(a, s);

a += b;

return a;

}

private final int HH( int a, int b, int c, int d, int x, int s, int ac) {

a += (H(b, c, d) + x + ac);

a = rotate_left(a, s);

a += b;

return a;

}

private final int II( int a, int b, int c, int d, int x, int s, int ac) {

a += (I(b, c, d) + x + ac);

a = rotate_left(a, s);

a += b;

return a;

}

private final void decode( int output[], byte input[], int off, int len) {

int i = 0 ;

int j = 0 ;

for (; j len; i ++ , j += 4 ) {

output[i] = ((( int ) (input[off + j] & 0xff ))

| ((( int ) (input[off + j + 1 ] & 0xff )) << 8 )

| ((( int ) (input[off + j + 2 ] & 0xff )) << 16) | (((int ) (input[off

+ j + 3 ] & 0xff )) << 24 ));

}

private final void transform( byte block[], int offset) {

int a = state[ 0 ];

int b = state[ 1 ];

int c = state[ 2 ];

int d = state[ 3 ];

int x[] = new int [ 16 ];

decode(x, block, offset, 64 );

/* Round 1 */

a = FF(a, b, c, d, x[ 0 ], S11, 0xd76aa478 ); /* 1 */

d = FF(d, a, b, c, x[ 1 ], S12, 0xe8c7b756 ); /* 2 */

c = FF(c, d, a, b, x[ 2 ], S13, 0x242070db ); /* 3 */

b = FF(b, c, d, a, x[ 3 ], S14, 0xc1bdceee ); /* 4 */

a = FF(a, b, c, d, x[ 4 ], S11, 0xf57c0faf ); /* 5 */

d = FF(d, a, b, c, x[ 5 ], S12, 0x4787c62a ); /* 6 */

c = FF(c, d, a, b, x[ 6 ], S13, 0xa8304613 ); /* 7 */

b = FF(b, c, d, a, x[ 7 ], S14, 0xfd469501 ); /* 8 */

a = FF(a, b, c, d, x[ 8 ], S11, 0x698098d8 ); /* 9 */

d = FF(d, a, b, c, x[ 9 ], S12, 0x8b44f7af ); /* 10 */

c = FF(c, d, a, b, x[ 10 ], S13, 0xffff5bb1 ); /* 11 */

b = FF(b, c, d, a, x[ 11 ], S14, 0x895cd7be ); /* 12 */

a = FF(a, b, c, d, x[ 12 ], S11, 0x6b901122 ); /* 13 */

d = FF(d, a, b, c, x[ 13 ], S12, 0xfd987193 ); /* 14 */

c = FF(c, d, a, b, x[ 14 ], S13, 0xa679438e ); /* 15 */

b = FF(b, c, d, a, x[ 15 ], S14, 0x49b40821 ); /* 16 */

/* Round 2 */

a = GG(a, b, c, d, x[ 1 ], S21, 0xf61e2562 ); /* 17 */

d = GG(d, a, b, c, x[ 6 ], S22, 0xc040b340 ); /* 18 */

c = GG(c, d, a, b, x[ 11 ], S23, 0x265e5a51 ); /* 19 */

b = GG(b, c, d, a, x[ 0 ], S24, 0xe9b6c7aa ); /* 20 */

a = GG(a, b, c, d, x[ 5 ], S21, 0xd62f105d ); /* 21 */

d = GG(d, a, b, c, x[ 10 ], S22, 0x2441453 ); /* 22 */

c = GG(c, d, a, b, x[ 15 ], S23, 0xd8a1e681 ); /* 23 */

b = GG(b, c, d, a, x[ 4 ], S24, 0xe7d3fbc8 ); /* 24 */

a = GG(a, b, c, d, x[ 9 ], S21, 0x21e1cde6 ); /* 25 */

d = GG(d, a, b, c, x[ 14 ], S22, 0xc33707d6 ); /* 26 */

c = GG(c, d, a, b, x[ 3 ], S23, 0xf4d50d87 ); /* 27 */

b = GG(b, c, d, a, x[ 8 ], S24, 0x455a14ed ); /* 28 */

a = GG(a, b, c, d, x[ 13 ], S21, 0xa9e3e905 ); /* 29 */

d = GG(d, a, b, c, x[ 2 ], S22, 0xfcefa3f8 ); /* 30 */

c = GG(c, d, a, b, x[ 7 ], S23, 0x676f02d9 ); /* 31 */

b = GG(b, c, d, a, x[ 12 ], S24, 0x8d2a4c8a ); /* 32 */

/* Round 3 */

a = HH(a, b, c, d, x[ 5 ], S31, 0xfffa3942 ); /* 33 */

d = HH(d, a, b, c, x[ 8 ], S32, 0x8771f681 ); /* 34 */

c = HH(c, d, a, b, x[ 11 ], S33, 0x6d9d6122 ); /* 35 */

b = HH(b, c, d, a, x[ 14 ], S34, 0xfde5380c ); /* 36 */

a = HH(a, b, c, d, x[ 1 ], S31, 0xa4beea44 ); /* 37 */

d = HH(d, a, b, c, x[ 4 ], S32, 0x4bdecfa9 ); /* 38 */

c = HH(c, d, a, b, x[ 7 ], S33, 0xf6bb4b60 ); /* 39 */

b = HH(b, c, d, a, x[ 10 ], S34, 0xbebfbc70 ); /* 40 */

a = HH(a, b, c, d, x[ 13 ], S31, 0x289b7ec6 ); /* 41 */

d = HH(d, a, b, c, x[ 0 ], S32, 0xeaa127fa ); /* 42 */

c = HH(c, d, a, b, x[ 3 ], S33, 0xd4ef3085 ); /* 43 */

b = HH(b, c, d, a, x[ 6 ], S34, 0x4881d05 ); /* 44 */

a = HH(a, b, c, d, x[ 9 ], S31, 0xd9d4d039 ); /* 45 */

d = HH(d, a, b, c, x[ 12 ], S32, 0xe6db99e5 ); /* 46 */

c = HH(c, d, a, b, x[ 15 ], S33, 0x1fa27cf8 ); /* 47 */

b = HH(b, c, d, a, x[ 2 ], S34, 0xc4ac5665 ); /* 48 */

/* Round 4 */

a = II(a, b, c, d, x[ 0 ], S41, 0xf4292244 ); /* 49 */

d = II(d, a, b, c, x[ 7 ], S42, 0x432aff97 ); /* 50 */

c = II(c, d, a, b, x[ 14 ], S43, 0xab9423a7 ); /* 51 */

b = II(b, c, d, a, x[ 5 ], S44, 0xfc93a039 ); /* 52 */

a = II(a, b, c, d, x[ 12 ], S41, 0x655b59c3 ); /* 53 */

d = II(d, a, b, c, x[ 3 ], S42, 0x8f0ccc92 ); /* 54 */

c = II(c, d, a, b, x[ 10 ], S43, 0xffeff47d ); /* 55 */

b = II(b, c, d, a, x[ 1 ], S44, 0x85845dd1 ); /* 56 */

a = II(a, b, c, d, x[ 8 ], S41, 0x6fa87e4f ); /* 57 */

d = II(d, a, b, c, x[ 15 ], S42, 0xfe2ce6e0 ); /* 58 */

c = II(c, d, a, b, x[ 6 ], S43, 0xa3014314 ); /* 59 */

b = II(b, c, d, a, x[ 13 ], S44, 0x4e0811a1 ); /* 60 */

a = II(a, b, c, d, x[ 4 ], S41, 0xf7537e82 ); /* 61 */

d = II(d, a, b, c, x[ 11 ], S42, 0xbd3af235 ); /* 62 */

c = II(c, d, a, b, x[ 2 ], S43, 0x2ad7d2bb ); /* 63 */

b = II(b, c, d, a, x[ 9 ], S44, 0xeb86d391 ); /* 64 */

state[ 0 ] += a;

state[ 1 ] += b;

state[ 2 ] += c;

state[ 3 ] += d;

}

private final void update( byte input[], int len) {

int index = (( int ) (count >> 3 )) & 0x3f ;

count += (len << 3 );

int partLen = 64 - index;

int i = 0 ;

if (len >= partLen) {

System.arraycopy(input, 0 , buffer, index, partLen);

transform(buffer, 0 );

for (i = partLen; i + 63 len; i += 64 )

transform(input, i);

index = 0 ;

} else {

i = 0 ;

}

System.arraycopy(input, i, buffer, index, len - i);

}

private byte [] end() {

byte bits[] = new byte [ 8 ];

for ( int i = 0 ; i 8 ; i ++ )

bits[i] = ( byte ) ((count >>> (i * 8 )) & 0xff );

int index = (( int ) (count >> 3 )) & 0x3f ;

int padlen = (index 56 ) ? ( 56 - index) : ( 120 - index);

update(padding, padlen);

update(bits, 8 );

return encode(state, 16 );

}

// Encode the content.state array into 16 bytes array

private byte [] encode( int input[], int len) {

byte output[] = new byte [len];

int i = 0 ;

int j = 0 ;

for (; j len; i ++ , j += 4 ) {

output[j] = ( byte ) ((input[i]) & 0xff );

output[j + 1 ] = ( byte ) ((input[i] >> 8 ) & 0xff );

output[j + 2 ] = ( byte ) ((input[i] >> 16 ) & 0xff );

output[j + 3 ] = ( byte ) ((input[i] >> 24 ) & 0xff );

}

return output;

}

/**

* Get the digest for our input stream. This method constructs the input

* stream digest, and return it, as a a String, following the MD5 (rfc1321)

* algorithm,

* @return An instance of String, giving the message digest.

* @exception IOException

* Thrown if the digestifier was unable to read the input

* stream.

public byte [] getDigest() throws IOException {

byte buffer[] = new byte [BUFFER_SIZE];

int got = - 1 ;

if (digest != null )

return digest;

while ((got = in.read(buffer)) > 0 )

update(buffer, got);

this .digest = end();

return digest;

}

/**

* Get the digest, for this string digestifier. This method doesn't throw

* any IOException, since it knows that the underlying stream ws built from

* a String.

public byte [] processString() {

if ( ! stringp)

throw new RuntimeException( this .getClass().getName()

+ " [processString] " + " not a string. " );

try {

return getDigest();

} catch (IOException ex) {

}

throw new RuntimeException( this .getClass().getName()

+ " [processString] " + " : implementation error. " );

}

/**

* Get the digest, as a proper string.

public String getStringDigest() {

if (digest == null )

throw new RuntimeException( this .getClass().getName()

+ " [getStringDigest] " + " : called before processing. " );

return stringify(digest);

}

/**

* Construct a digestifier for the given string.

* @param input

* The string to be digestified.

* @param encoding

* the encoding name used (such as UTF8)

public MD5(String input, String enc) {

byte bytes[] = null ;

try {

bytes = input.getBytes(enc);

} catch (UnsupportedEncodingException e) {

throw new RuntimeException( " no " + enc + " encoding!!! " );

}

this .stringp = true ;

this .in = new ByteArrayInputStream(bytes);

this .state = new int [ 4 ];

this .buffer = new byte [ 64 ];

this .count = 0 ;

state[ 0 ] = 0x67452301 ;

state[ 1 ] = 0xefcdab89 ;

state[ 2 ] = 0x98badcfe ;

state[ 3 ] = 0x10325476 ;

}

/**

* Construct a digestifier for the given string.

* @param input

* The string to be digestified.

public MD5(String input) {

this (input, " UTF8 " );

}

/**

* Construct a digestifier for the given input stream.

* @param in

* The input stream to be digestified.

public MD5(InputStream in) {

this .stringp = false ;

this .in = in;

this .state = new int [ 4 ];

this .buffer = new byte [ 64 ];

this .count = 0 ;

state[ 0 ] = 0x67452301 ;

state[ 1 ] = 0xefcdab89 ;

state[ 2 ] = 0x98badcfe ;

state[ 3 ] = 0x10325476 ;

}

public static void main(String args[]) throws IOException {

if (args.length != 1 ) {

System.out.println( " Md5 " );

System.exit( 1 );

}

MD5 md5 = new MD5( new FileInputStream( new File(args[ 0 ])));

byte b[] = md5.getDigest();

System.out.println(stringify(b));

}

posted on 2006-07-13 17:25 风人园阅读(1476) 评论(0) 编辑收藏所属分类: Java

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