Pool


1   /**
2    * Copyright (C) 2001-2002
3    * - France Telecom R&D
4    * - Laboratoire Logiciels, Systemes, Reseaux - UMR 5526, CNRS-INPG-UJF
5    *
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2 of the License, or (at your option) any later version.
10   *
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   *
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
19   *
20   * Release: 1.0
21   *
22   * Authors:
23   *
24   */
25  
26  package org.objectweb.perseus.pool.api;
27  
28  import org.objectweb.perseus.dependency.api.DeadLockException;
29  
30  import java.util.Collection  ;
31  
32  
33  /**
34   * The interface <b>Pool</b> defines an object that pools resources of any
35   * kind. Resources must be requested (getResource) and released
36   * (releaseResource) on demand. A Pool object can be parameterized along
37   * different dimensions. All these dimensions are represented by PoolAttributes
38   * interface.
39   */
40  public interface Pool {
41  
42      /**
43       * <b>getResource</b> is used to allocate a PoolResource from the Pool.
44       * Some hints are passed in order to specialise the matching or creation
45       * of PoolResource.
46       * @param hints Some properties to specialise the matching or the creation
47       *              of PoolResource.
48       * @return      The PoolResource allocated from the Pool.
49       */
50      Object   getResource(Object   hints) throws PoolException;
51  
52      /**
53       * <b>getResource</b> is used to allocate a PoolResource from the Pool.
54       * Some hints are passed in order to specialise the matching or creation
55       * of PoolResource. The user parameter avoids dead lock by the use of a
56       * dependency graph.
57       * @param hints Some properties to specialise the matching or the creation
58       *              of PoolResource.
59       * @param user is an identifier of the context wanting a resource in the
60       * pool.
61       * @return      The PoolResource allocated from the Pool.
62       */
63      Object   getResource(Object   hints, Object   user)
64              throws PoolException, DeadLockException;
65  
66      /**
67       * <b>releaseResource</b> releases a PoolResource in order to allow the
68       * Pool to recycle this PoolResource.
69       * @param resource  The PoolResource to be released.
70       */
71      void releaseResource(Object   resource) throws PoolException;
72      
73      /**
74       * @return the number resource used and free
75       */
76      int getSize();
77      
78      /**
79       * @return the number of unsused resource 
80       */
81      int getFreeResourceNumber();
82  
83      /**
84       * @return the number of used resource 
85       */
86      int getUsedResourceNumber();
87      
88      /**
89       * @return collection of user. The collection can be empty even if resource
90       * are used, in case of the user did not specify any reference on 
91       * getResource. 
92       */
93      Collection   getUsers();
94  
95  
96  }
97
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