生成24位字符串ID__IdGenerator.java

此工具类用于生成24位字符串ID，唯一不重复。

直接通过 IdGenerator.get() 获取。

源码如下：(点击下载源码 - IdGenerator.java )

  1 import java.net.NetworkInterface;
  2 import java.nio.ByteBuffer;
  3 import java.nio.ByteOrder;
  4 import java.util.Enumeration;
  5
  6 /**
  7  * 生成24位字符串ID
  8  *
  9  */
 10 public class IdGenerator implements Comparable<IdGenerator> {
 11
 12     /**
 13      * 调用该方法获取24位字符串ID
 14      * @return
 15      */
 16     public static String get() {
 17         return new IdGenerator().toString();
 18     }
 19
 20     public IdGenerator() {
 21         _time = _gentime;
 22         _machine = _genmachine;
 23         synchronized (_incLock) {
 24             _inc = _nextInc++;
 25         }
 26         _new = true;
 27     }
 28
 29     public int hashCode() {
 30         return _inc;
 31     }
 32
 33     public String toStringMongod() {
 34         byte b[] = toByteArray();
 35
 36         StringBuilder buf = new StringBuilder(24);
 37
 38         for (int i = 0; i < b.length; i++) {
 39             int x = b[i] & 0xFF;
 40             String s = Integer.toHexString(x);
 41             if (s.length() == 1)
 42                 buf.append("0");
 43             buf.append(s);
 44         }
 45
 46         return buf.toString();
 47     }
 48
 49     public byte[] toByteArray() {
 50         byte b[] = new byte[12];
 51         ByteBuffer bb = ByteBuffer.wrap(b);
 52         bb.putInt(_inc);
 53         bb.putInt(_machine);
 54         bb.putInt(_time);
 55         reverse(b);
 56         return b;
 57     }
 58
 59     static void reverse(byte[] b) {
 60         for (int i = 0; i < b.length / 2; i++) {
 61             byte t = b[i];
 62             b[i] = b[b.length - (i + 1)];
 63             b[b.length - (i + 1)] = t;
 64         }
 65     }
 66
 67     static String _pos(String s, int p) {
 68         return s.substring(p * 2, (p * 2) + 2);
 69     }
 70
 71     public String toString() {
 72         return toStringMongod();
 73     }
 74
 75     public int compareTo(IdGenerator id) {
 76         if (id == null)
 77             return -1;
 78
 79         long xx = id.getTime() - getTime();
 80         if (xx > 0)
 81             return -1;
 82         else if (xx < 0)
 83             return 1;
 84
 85         int x = id._machine - _machine;
 86         if (x != 0)
 87             return -x;
 88
 89         x = id._inc - _inc;
 90         if (x != 0)
 91             return -x;
 92
 93         return 0;
 94     }
 95
 96     public int getMachine() {
 97         return _machine;
 98     }
 99
100     public long getTime() {
101         long z = _flip(_time);
102         return z * 1000;
103     }
104
105     public int getInc() {
106         return _inc;
107     }
108
109     final int _time;
110     final int _machine;
111     final int _inc;
112
113     boolean _new;
114
115     static int _flip(int x) {
116         byte b[] = new byte[4];
117         ByteBuffer bb = ByteBuffer.wrap(b);
118         bb.order(ByteOrder.LITTLE_ENDIAN);
119         bb.putInt(x);
120         bb.flip();
121         bb.order(ByteOrder.BIG_ENDIAN);
122         return bb.getInt();
123     }
124
125     private static int _nextInc = (new java.util.Random()).nextInt();
126     private static final String _incLock = new String("IdGenerator._incLock");
127
128     private static int _gentime = _flip((int) (System.currentTimeMillis() / 1000));
129
130     static final Thread _timeFixer;
131     private static final int _genmachine;
132     static {
133         try {
134             final int machinePiece;
135             {
136                 StringBuilder sb = new StringBuilder();
137                 Enumeration<NetworkInterface> e = NetworkInterface.getNetworkInterfaces();
138                 while (e.hasMoreElements()) {
139                     NetworkInterface ni = e.nextElement();
140                     sb.append(ni.toString());
141                 }
142                 machinePiece = sb.toString().hashCode() << 16;
143             }
144
145             final int processPiece = java.lang.management.ManagementFactory.getRuntimeMXBean().getName().hashCode() & 0xFFFF;
146             _genmachine = machinePiece | processPiece;
147         } catch (java.io.IOException ioe) {
148             throw new RuntimeException(ioe);
149         }
150
151         _timeFixer = new Thread("IdGenerator-TimeFixer") {
152             public void run() {
153                 while (true) {
154                     try {
155                         Thread.sleep(499);
156                     } catch (InterruptedException e) {
157                     }
158                     _gentime = _flip((int) (System.currentTimeMillis() / 1000));
159                 }
160             }
161         };
162         _timeFixer.setDaemon(true);
163         _timeFixer.start();
164     }
165
166 }