01: /**
02: * Copyright (C) 2006 NetMind Consulting Bt.
03: *
04: * This library is free software; you can redistribute it and/or
05: * modify it under the terms of the GNU Lesser General Public
06: * License as published by the Free Software Foundation; either
07: * version 3 of the License, or (at your option) any later version.
08: *
09: * This library is distributed in the hope that it will be useful,
10: * but WITHOUT ANY WARRANTY; without even the implied warranty of
11: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12: * Lesser General Public License for more details.
13: *
14: * You should have received a copy of the GNU Lesser General Public
15: * License along with this library; if not, write to the Free Software
16: * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17: */package hu.netmind.persistence;
18:
19: import java.util.Date;
20:
21: /**
22: * This class tracks the serials given out to this instance.
23: * @author Brautigam Robert
24: * @version Revision: $Revision$
25: */
26: public class SerialTracker {
27: private long offset = 0;
28: private long lastSerial = 0;
29: private int subSerial = 0;
30:
31: /**
32: * Set the offset for serial numbers. To determine the offset,
33: * a valid serial must be given to this method, and the difference
34: * between it and the current serial will be added to the current offset,
35: * if it's positive.
36: */
37: public void adjustOffset(Long serial) {
38: long serialCooked = 10000 * (serial.longValue() / 10000 + 1); // Chop off sub-serial
39: Long currentSerial = getNextSerial();
40: long currentCooked = 10000 * (currentSerial.longValue() / 10000 + 1); // Chop of sub-serial
41: if (serialCooked > currentCooked) {
42: // Current serial should be greated or equal to the supplied
43: // serial. If it's not, then it has to be corrected
44: offset += (serialCooked - currentCooked);
45: }
46: }
47:
48: /**
49: * Get the next serial for database functions.
50: */
51: public synchronized Long getNextSerial() {
52: // Get the serial from the current date. This is supposed to
53: // be millisecond precision.
54: long result = DateSerialUtil.getSerial(new Date());
55: result += offset;
56: // Implement sub-millisecond precision here
57: if (lastSerial == result) {
58: // This means we were executed in the same millisecond
59: // as last time. Add sub-serial number, and increase if possible.
60: if (subSerial >= 9999)
61: throw new StoreException(
62: "Serial number exhausted. More than 10.000 operations in the same millisecond. Wow. Is this the distant future? Do you sit in front of a quantum computer? ...Hm... Does it run Linux?");
63: subSerial++;
64: } else {
65: // If lastSerial is greater, then something is very wrong
66: if (lastSerial > result)
67: throw new StoreException(
68: "Next serial is in the past, something is wrong.");
69: // This is more likely. We are at least one milisecond further
70: // in time, so zero the subSerial number.
71: subSerial = 0;
72: }
73: // Return
74: lastSerial = result;
75: return new Long(result + subSerial);
76: }
77:
78: }
|