1 /***
2 * Copyright 2003-2010 Terracotta, Inc.
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
17 package net.sf.ehcache.util;
18
19 import java.util.Date;
20 import java.util.Timer;
21 import java.util.TimerTask;
22
23 /***
24 * A fail-safe timer in the sense that if the runtime environment restricts
25 * creating new threads, it doesn't blow up with an exception. TimerTasks that are
26 * scheduled will run at least once (inline when they are scheduled) if creating
27 * threads is not allowed.
28 * For example, Google App Engine does not allow creation of new threads.
29 * <p/>
30 * Clients should not use this as a general purpose timing service. To do so could
31 * interfere with the running of the Cache.
32 *
33 * @author <a href="mailto:asanoujam@terracottatech.com">Abhishek Sanoujam</a>
34 * @since 1.7
35 *
36 */
37 public class FailSafeTimer {
38
39 private final Timer timer;
40 private final boolean timerThreadRunning;
41
42 /***
43 * Constructor accepting a name for the timer. The scheduling thread is
44 * created as a daemon
45 *
46 * @param name
47 */
48 public FailSafeTimer(String name) {
49 boolean threadRunning;
50 Timer localTimer = null;
51 try {
52 localTimer = new Timer(name, true);
53 threadRunning = true;
54 } catch (Exception e) {
55 localTimer = null;
56 threadRunning = false;
57 }
58 this.timerThreadRunning = threadRunning;
59 this.timer = localTimer;
60 }
61
62 /***
63 * If the runtime environment restricts thread creation, this method does
64 * nothing.
65 *
66 * @see java.util.Timer#cancel()
67 */
68 public void cancel() {
69 if (timerThreadRunning) {
70 timer.cancel();
71 }
72 }
73
74 /***
75 * If the runtime environment restricts thread creation, this method does
76 * nothing.
77 *
78 * @see java.util.Timer#purge()
79 */
80 public int purge() {
81 if (timerThreadRunning) {
82 return timer.purge();
83 } else {
84 return 0;
85 }
86 }
87
88 /***
89 * If the runtime environment restricts thread creation, the task is run
90 * inline for only one time. No further repeated execution happens for the
91 * task
92 *
93 * @see java.util.Timer#schedule(java.util.TimerTask, java.util.Date, long)
94 */
95 public void schedule(TimerTask task, Date firstTime, long period) {
96 if (timerThreadRunning) {
97 timer.schedule(task, firstTime, period);
98 } else {
99 task.run();
100 }
101 }
102
103 /***
104 * If the runtime environment restricts thread creation, the task is run
105 * inline for only one time. No further repeated execution happens for the
106 * task
107 *
108 * @see java.util.Timer#schedule(java.util.TimerTask, java.util.Date)
109 */
110 public void schedule(TimerTask task, Date time) {
111 if (timerThreadRunning) {
112 timer.schedule(task, time);
113 } else {
114 task.run();
115 }
116 }
117
118 /***
119 * If the runtime environment restricts thread creation, the task is run
120 * inline for only one time. No further repeated execution happens for the
121 * task
122 *
123 * @see java.util.Timer#schedule(java.util.TimerTask, long, long)
124 */
125 public void schedule(TimerTask task, long delay, long period) {
126 if (timerThreadRunning) {
127 timer.schedule(task, delay, period);
128 } else {
129 task.run();
130 }
131 }
132
133 /***
134 * If the runtime environment restricts thread creation, the task is run
135 * inline for only one time. No further repeated execution happens for the
136 * task
137 *
138 * @see java.util.Timer#schedule(java.util.TimerTask, long)
139 */
140 public void schedule(TimerTask task, long delay) {
141 if (timerThreadRunning) {
142 timer.schedule(task, delay);
143 } else {
144 task.run();
145 }
146 }
147
148 /***
149 * If the runtime environment restricts thread creation, the task is run
150 * inline for only one time. No further repeated execution happens for the
151 * task
152 *
153 * @see java.util.Timer#scheduleAtFixedRate(java.util.TimerTask, java.util.Date, long)
154 */
155 public void scheduleAtFixedRate(TimerTask task, Date firstTime, long period) {
156 if (timerThreadRunning) {
157 timer.scheduleAtFixedRate(task, firstTime, period);
158 } else {
159 task.run();
160 }
161 }
162
163 /***
164 * If the runtime environment restricts thread creation, the task is run
165 * inline for only one time. No further repeated execution happens for the
166 * task
167 *
168 * @see java.util.Timer#scheduleAtFixedRate(java.util.TimerTask, long, long)
169 */
170 public void scheduleAtFixedRate(TimerTask task, long delay, long period) {
171 if (timerThreadRunning) {
172 timer.scheduleAtFixedRate(task, delay, period);
173 } else {
174 task.run();
175 }
176 }
177
178 }