| 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 / x86import 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 <</font>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()); System.out.println( new UUID()); 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 <</font>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 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( byte ) 0 , ( 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 <<</span> 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 )) <<</span> 8 ) | ((( int ) (input[off + j + 2 ] & 0xff )) <<</span> 16) | (((int ) (input[off + j + 3 ] & 0xff )) <<</span> 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 <<</span> 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)); }} |
