1 /*
2 * Copyright 2007-2013 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 public class IncrementFactory implements IdFactory
31 {
32 // ********************************* Fields *********************************
33
34 // --- constants ------------------------------------------------------------
35
36 // --- members --------------------------------------------------------------
37
38 /**
39 * Reference to the logger for this class.
40 */
41 private final Log log = LogFactory.getLog(IncrementFactory.class);
42
43 /**
44 * The thread-safe incrementor of long values.
45 */
46 private final AtomicLong atomic;
47
48 // ****************************** Initializer *******************************
49
50 // ****************************** Constructors ******************************
51
52 /**
53 * Default constructor with counter initialized with <code>1</code>.
54 */
55 public IncrementFactory()
56 {
57 this(1);
58 }
59
60 /**
61 * Convenience constructor.
62 *
63 * @param startValue the start value of the counter.
64 * @throws IllegalArgumentException if the start value is smaller than or
65 * equal to zero.
66 */
67 public IncrementFactory(final long startValue)
68 throws IllegalArgumentException
69 {
70 if (startValue <= 0L)
71 {
72 throw new IllegalArgumentException(
73 "Start value must be greater than zero, but is '" + startValue + "'.");
74 }
75 this.atomic = new AtomicLong(startValue);
76 }
77
78 // ****************************** Inner Classes *****************************
79
80 // ********************************* Methods ********************************
81
82 // --- init -----------------------------------------------------------------
83
84 // --- get&set --------------------------------------------------------------
85
86 // --- business -------------------------------------------------------------
87
88 @Override
89 public LongExceptionId createId()
90 {
91 boolean notSet;
92 long current;
93 do
94 {
95 current = atomic.getAndIncrement();
96 notSet = false;
97
98 if (current <= 0L)
99 {
100 final boolean success = atomic.compareAndSet(current + 1, 2);
101 if (success)
102 {
103 current = 1;
104 if (log.isInfoEnabled())
105 {
106 log.info("Increment factory resetted exception identifier to '1'.");
107 }
108 }
109 else
110 {
111 notSet = true;
112 }
113 }
114 }
115 while (notSet);
116
117 return new LongExceptionId(current);
118 }
119
120 // --- object basics --------------------------------------------------------
121 }