UUIDKeyGenerator


1   /*
2   * JBoss, Home of Professional Open Source
3   * Copyright 2005, JBoss Inc., and individual contributors as indicated
4   * by the @authors tag. See the copyright.txt in the distribution for a
5   * full listing of individual contributors.
6   *
7   * This is free software; you can redistribute it and/or modify it
8   * under the terms of the GNU Lesser General Public License as
9   * published by the Free Software Foundation; either version 2.1 of
10  * the License, or (at your option) any later version.
11  *
12  * This software is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with this software; if not, write to the Free
19  * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20  * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21  */
22  package org.jboss.ejb.plugins.keygenerator.uuid;
23  
24  import org.jboss.ejb.plugins.keygenerator.KeyGenerator;
25  
26  import java.net.InetAddress  ;
27  import java.security.SecureRandom  ;
28  
29  
30  /**
31   * The implementation of UUID key generator
32   * based on the algorithm from Floyd Marinescu's EJB Design Patterns.
33   *
34   * @author <a HREF="mailto:loubyansky@ukr.net">Alex Loubyansky</a>
35   *
36   * @version $Revision: 37459 $
37   */
38  public class UUIDKeyGenerator
39     implements KeyGenerator
40  {
41  
42     // Attributes ---------------------------------------------------
43  
44     /** secure random to provide nonrepeating seed */
45     SecureRandom   seeder;
46  
47     /** cached middle value */
48     private String   midValue;
49  
50     // Constructor --------------------------------------------------
51  
52     public UUIDKeyGenerator()
53        throws Exception  
54     {
55        // cache the middle part for UUID
56  
57        StringBuffer   buffer = new StringBuffer  ( 16 );
58  
59        // construct host part of the uuid (8 hex digits)
60        byte[] addr = InetAddress.getLocalHost().getAddress();
61        buffer.append( toHex( toInt(addr), 8 ) );
62  
63        // append the hash code for this object (8 hex digits)
64        buffer.append( toHex( System.identityHashCode(this), 8 ) );
65  
66        // set up midValue
67        midValue = buffer.toString();
68  
69        // load up the randomizer
70        seeder = new SecureRandom  ();
71        int node = seeder.nextInt();
72     }
73  
74     // KeyGenerator implementation ----------------------------------
75  
76     public Object   generateKey()
77     {
78        StringBuffer   buffer = new StringBuffer  ( 32 );
79  
80        // append current time as unsigned int value
81        buffer.append(toHex((int)(System.currentTimeMillis() & 0xFFFFFFFF), 8));
82  
83        // append cached midValue
84        buffer.append( midValue );
85  
86        // append the next random int
87        buffer.append( toHex( seeder.nextInt(), 8 ) );
88  
89        // return the result
90        return buffer.toString();
91     }
92  
93     // Private ------------------------------------------------------
94  
95     /**
96      * Converts int value to string hex representation
97      */
98     private String   toHex( int value, int length )
99     {
100       // hex digits
101       char[] hexDigits =
102          { '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F' };
103 
104       StringBuffer   buffer = new StringBuffer  ( length );
105       int shift = (length - 1) << 2;
106       int i = -1;
107       while( ++i < length )
108       {
109          buffer.append( hexDigits[(value >> shift) & 0x0000000F] );
110          value <<= 4;
111       }
112       return buffer.toString();
113    }
114 
115    /**
116     * Constructs int value from byte array
117     */
118    private static int toInt( byte[] bytes )
119    {
120       int value = 0;
121       int i = -1;
122       while( ++i < bytes.length )
123       {
124          value <<= 8;
125          int b = bytes[ i ] & 0xff;
126          value |= b;
127       }
128       return value;
129    }
130 }
131
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