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Java > Open Source Codes > example > PeriodicTask


1 package example;
2
3 import com.caucho.log.Log;
4 import com.caucho.util.L10N;
5 import java.util.logging.Level JavaDoc;
6 import java.util.logging.Logger JavaDoc;
7
8 public class PeriodicTask
9  implements PeriodicTaskMBean, javax.resource.spi.work.Work JavaDoc
10 {
11   static protected final Logger JavaDoc log =
12     Logger.getLogger(PeriodicTask.class.getName());
13
14   private long _estimatedAverageTime = 5000;
15
16   private boolean _isActive = false;
17   private long _lastActiveTime = -1;
18   private long _totalActiveCount = 0;
19   private long _totalActiveTime = 0;
20
21
22   public PeriodicTask()
23   {
24   }
25
26   /**
27    * {@inheritDoc}
28    */
29   public void setEstimatedAverageTime(long estimatedAverageTime)
30   {
31     _estimatedAverageTime = estimatedAverageTime;
32   }
33
34   /**
35    * {@inheritDoc}
36    */
37   public long getEstimatedAverageTime()
38   {
39     return _estimatedAverageTime;
40   }
41
42   public void init()
43     throws Exception JavaDoc
44   {
45   }
46
47   /**
48    * {@inheritDoc}
49    */
50   public boolean isActive()
51   {
52     synchronized (this) {
53       return _isActive == true;
54     }
55   }
56
57   /**
58    * {@inheritDoc}
59    */
60   public long getEstimatedTimeRemaining()
61   {
62     synchronized (this) {
63       if (_isActive) {
64         long now = System.currentTimeMillis();
65         long activeTime = now - _lastActiveTime;
66         long estimate = getAverageActiveTime() - activeTime;
67         if (estimate < 0)
68           return 1000;
69         else
70           return estimate;
71       }
72       else
73         return 0;
74     }
75   }
76
77   /**
78    * {@inheritDoc}
79    */
80   public long getLastActiveTime()
81   {
82     return _lastActiveTime;
83   }
84
85   /**
86    * {@inheritDoc}
87    */
88   public long getTotalActiveCount()
89   {
90     return _totalActiveCount;
91   }
92
93   /**
94    * {@inheritDoc}
95    */
96   public long getTotalActiveTime()
97   {
98     return _totalActiveTime;
99   }
100
101   /**
102    * {@inheritDoc}
103    */
104   public long getAverageActiveTime()
105   {
106     synchronized (this) {
107       long count = _isActive ? _totalActiveCount -1 : _totalActiveCount;
108       if (count < 1)
109         return _estimatedAverageTime;
110       else
111         return _totalActiveTime / count;
112     }
113   }
114
115   /**
116    * {@inheritDoc}
117    *
118    * Various statistical information is collected and maintained by this method,
119    * the actual task is performed by the performTask() method.
120    */
121   public void run()
122   {
123     synchronized (this) {
124       if (_isActive == true)
125         return;
126       _isActive = true;
127
128       _lastActiveTime = System.currentTimeMillis();
129       _totalActiveCount++;
130     }
131
132     try {
133       log.fine("performing task");
134
135       performTask();
136
137       log.fine("done performing task");
138     }
139     catch (Exception JavaDoc ex) {
140       log.log(Level.WARNING,"task failed",ex);
141     }
142     finally {
143       synchronized (this) {
144         _totalActiveTime += (System.currentTimeMillis() - _lastActiveTime);
145         _isActive = false;
146       }
147     }
148   }
149
150   protected void performTask()
151     throws Exception JavaDoc
152   {
153     // for the purposes of this tutorial, sleep for 10 seconds
154 // to imitate a task that takes 10 seconds to perform
155 Thread.sleep(10 * 1000L);
156   }
157
158   /**
159    * Required implementation of javax.resource.spi.work.Work.release()
160    */
161   public void release()
162   {
163   }
164 }
165
166
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