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1   /***
2    * Redistribution and use of this software and associated documentation
3    * ("Software"), with or without modification, are permitted provided
4    * that the following conditions are met:
5    *
6    * 1. Redistributions of source code must retain copyright
7    *    statements and notices.  Redistributions must also contain a
8    *    copy of this document.
9    *
10   * 2. Redistributions in binary form must reproduce the
11   *    above copyright notice, this list of conditions and the
12   *    following disclaimer in the documentation and/or other
13   *    materials provided with the distribution.
14   *
15   * 3. The name "Exolab" must not be used to endorse or promote
16   *    products derived from this Software without prior written
17   *    permission of Exoffice Technologies.  For written permission,
18   *    please contact info@exolab.org.
19   *
20   * 4. Products derived from this Software may not be called "Exolab"
21   *    nor may "Exolab" appear in their names without prior written
22   *    permission of Exoffice Technologies. Exolab is a registered
23   *    trademark of Exoffice Technologies.
24   *
25   * 5. Due credit should be given to the Exolab Project
26   *    (http://www.exolab.org/).
27   *
28   * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
29   * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
30   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
31   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
32   * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
33   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
34   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
37   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
39   * OF THE POSSIBILITY OF SUCH DAMAGE.
40   *
41   * Copyright 2000-2004 (C) Exoffice Technologies Inc. All Rights Reserved.
42   */
43  package org.exolab.jms.scheduler;
44  
45  import EDU.oswego.cs.dl.util.concurrent.LinkedQueue;
46  import EDU.oswego.cs.dl.util.concurrent.PooledExecutor;
47  import org.exolab.jms.common.threads.ThreadPoolFactory;
48  import org.exolab.jms.config.Configuration;
49  import org.exolab.jms.config.SchedulerConfiguration;
50  import org.exolab.jms.service.Service;
51  
52  
53  /***
54   * The scheduler is responsible for executing {@link Runnable} objects using a
55   * thread pool. Clients can add these objects to the scheduler and the scheduler
56   * will, in fifo order, execute them. If there are no threads currently
57   * available, the runnable will wait for one to become available.
58   * <p/>
59   * A client can add or remove {@link Runnable} objects.
60   *
61   * @author <a href="mailto:mourikis@intalio.com">Jim Mourikis</a>
62   * @author <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
63   * @author <a href="mailto:jima@comware.com.au">Jim Alateras</a>
64   * @version $Revision: 1.3 $ $Date: 2006/02/23 11:17:39 $
65   */
66  public class Scheduler extends Service {
67  
68      /***
69       * The thread pool used by the scheduler.
70       */
71      private final PooledExecutor _threads;
72  
73      /***
74       * This is the minimum number of threads that can be used to configure the
75       * scheduler. If a lower nmber is specified then it defaults to this value
76       */
77      private final static int MIN_THREAD_COUNT = 2;
78  
79      /***
80       * Unique name identifyting this sevice
81       */
82      private static final String SCHEDULER_NAME = "Scheduler";
83  
84      /***
85       * Construct a new <code>Scheduler</code>.
86       *
87       * @param config  the configuration
88       * @param factory the thread pool factory
89       */
90      public Scheduler(Configuration config, ThreadPoolFactory factory) {
91          super(SCHEDULER_NAME);
92  
93          SchedulerConfiguration schedConfig =
94                  config.getSchedulerConfiguration();
95  
96          int count = schedConfig.getMaxThreads();
97          if (count < MIN_THREAD_COUNT) {
98              count = MIN_THREAD_COUNT;
99          }
100 
101         // create the thread pool
102         _threads = factory.create(SCHEDULER_NAME, new LinkedQueue(), count);
103         _threads.setMinimumPoolSize(count);
104         _threads.setKeepAliveTime(-1); // live forever
105     }
106 
107     /***
108      * Add a Runnable object to the scheduler queue. When a thread becomes
109      * available, it will be executed.
110      *
111      * @param task the task to execute
112      */
113     public void execute(Runnable task) throws InterruptedException {
114         _threads.execute(task);
115     }
116 
117     /***
118      * Stop the service.
119      */
120     protected void doStop() {
121         _threads.shutdownAfterProcessingCurrentlyQueuedTasks();
122     }
123 
124 }