KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > org > jboss > aspects > concurrent > SemaphoreAspect


1 /*
2   * JBoss, Home of Professional Open Source
3   * Copyright 2005, JBoss Inc., and individual contributors as indicated
4   * by the @authors tag. See the copyright.txt in the distribution for a
5   * full listing of individual contributors.
6   *
7   * This is free software; you can redistribute it and/or modify it
8   * under the terms of the GNU Lesser General Public License as
9   * published by the Free Software Foundation; either version 2.1 of
10   * the License, or (at your option) any later version.
11   *
12   * This software is distributed in the hope that it will be useful,
13   * but WITHOUT ANY WARRANTY; without even the implied warranty of
14   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15   * Lesser General Public License for more details.
16   *
17   * You should have received a copy of the GNU Lesser General Public
18   * License along with this software; if not, write to the Free
19   * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20   * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21   */
22 package org.jboss.aspects.concurrent;
23
24 import org.jboss.aop.joinpoint.Invocation;
25
26 import java.util.concurrent.Semaphore JavaDoc;
27
28 /**
29  * comment
30  *
31  * @author <a HREF="mailto:bill@jboss.org">Bill Burke</a>
32  */
33 public class SemaphoreAspect
34 {
35    protected SemaphoreLocked props;
36
37    public SemaphoreAspect(SemaphoreLocked locked)
38    {
39       this.props = locked;
40    }
41
42    public Object JavaDoc acquire(Invocation invocation) throws Throwable JavaDoc
43    {
44       SemaphoredObject obj = (SemaphoredObject)invocation.getTargetObject();
45
46       if (props.timeout() == -1)
47       {
48             blockIndefinately(obj.getSemaphore());
49       }
50       else if (props.timeout() == 0)
51       {
52          tryLock(obj.getSemaphore());
53       }
54       else
55       {
56          tryLockWithTimeout(obj.getSemaphore());
57       }
58
59       try
60       {
61          return invocation.invokeNext();
62       }
63       finally
64       {
65          obj.getSemaphore().release(props.permits());
66       }
67    }
68
69    protected void blockIndefinately(Semaphore JavaDoc semaphore)
70    {
71       try
72       {
73          semaphore.acquire(props.permits());
74       }
75       catch (InterruptedException JavaDoc e)
76       {
77          throw new LockAcquisitionFailureException("Failed to acquire permit for @Semaphored class", e);
78       }
79    }
80
81    protected void tryLock(Semaphore JavaDoc semaphore)
82    {
83       if (!semaphore.tryAcquire(props.permits()))
84       {
85          throw new LockAcquisitionFailureException("Failed to acquire permit for @Semaphored class");
86       }
87    }
88
89    protected void tryLockWithTimeout(Semaphore JavaDoc semaphore)
90    {
91       try
92       {
93          if (!semaphore.tryAcquire(props.timeout(), props.unit()))
94          {
95             throw new LockAcquisitionFailureException("Failed to acquire permit for @Semaphored class. Timeout reached.");
96          }
97       }
98       catch (InterruptedException JavaDoc e)
99       {
100          throw new LockAcquisitionFailureException("Failed to acquire permit for @Semaphored class", e);
101       }
102    }
103 }
104
Popular Tags