1 /*
2 * Copyright 2007-2011 smartics, Kronseder & Reiner GmbH
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16 package de.smartics.exceptions.id;
17
18 import java.util.concurrent.atomic.AtomicLong;
19
20 import org.apache.commons.logging.Log;
21 import org.apache.commons.logging.LogFactory;
22
23 import de.smartics.exceptions.core.IdFactory;
24
25 /**
26 * The factory that created {@link de.smartics.exceptions.core.ExceptionId}s
27 * that provides a number that is larger than zero. If the last number has been
28 * provided, it continues with 1, issuing a message on info level.
29 *
30 * @author <a href="mailto:robert.reiner@smartics.de">Robert Reiner</a>
31 * @version $Revision$
32 */
33 public class IncrementFactory implements IdFactory
34 {
35 // ********************************* Fields *********************************
36
37 // --- constants ------------------------------------------------------------
38
39 // --- members --------------------------------------------------------------
40
41 /**
42 * Reference to the logger for this class.
43 */
44 private final Log log = LogFactory.getLog(IncrementFactory.class);
45
46 /**
47 * The thread-safe incrementor of long values.
48 */
49 private final AtomicLong atomic;
50
51 // ****************************** Initializer *******************************
52
53 // ****************************** Constructors ******************************
54
55 /**
56 * Default constructor with counter initialized with <code>1</code>.
57 */
58 public IncrementFactory()
59 {
60 this(1);
61 }
62
63 /**
64 * Convenience constructor.
65 *
66 * @param startValue the start value of the counter.
67 * @throws IllegalArgumentException if the start value is smaller than or
68 * equal to zero.
69 */
70 public IncrementFactory(final long startValue)
71 throws IllegalArgumentException
72 {
73 if (startValue <= 0L)
74 {
75 throw new IllegalArgumentException(
76 "Start value must be greater than zero, but is '" + startValue + "'.");
77 }
78 this.atomic = new AtomicLong(startValue);
79 }
80
81 // ****************************** Inner Classes *****************************
82
83 // ********************************* Methods ********************************
84
85 // --- init -----------------------------------------------------------------
86
87 // --- get&set --------------------------------------------------------------
88
89 // --- business -------------------------------------------------------------
90
91 /**
92 * {@inheritDoc}
93 *
94 * @see de.smartics.exceptions.core.IdFactory#createId()
95 */
96 public LongExceptionId createId()
97 {
98 boolean notSet;
99 long current;
100 do
101 {
102 current = atomic.getAndIncrement();
103 notSet = false;
104
105 if (current <= 0L)
106 {
107 final boolean success = atomic.compareAndSet(current + 1, 2);
108 if (success)
109 {
110 current = 1;
111 if (log.isInfoEnabled())
112 {
113 log.info("Increment factory resetted exception identifier to '1'.");
114 }
115 }
116 else
117 {
118 notSet = true;
119 }
120 }
121 }
122 while (notSet);
123
124 return new LongExceptionId(current);
125 }
126
127 // --- object basics --------------------------------------------------------
128 }