Pool


1   /* 
2    * Copyright 1999-2004 The Apache Software Foundation
3    * Licensed  under the  Apache License,  Version 2.0  (the "License");
4    * you may not use  this file  except in  compliance with the License.
5    * You may obtain a copy of the License at 
6    * 
7    *   http://www.apache.org/licenses/LICENSE-2.0
8    * 
9    * Unless required by applicable law or agreed to in writing, software
10   * distributed  under the  License is distributed on an "AS IS" BASIS,
11   * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
12   * implied.
13   * 
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.excalibur.mpool;
18  
19  /**
20   * This interface is to define how a Pool is used.  We have determined by
21   * using the previous Pool implementations that the Pool marker interface
22   * is considered harmful.  When generics are introduced in JDK 1.5, this
23   * interface will be a prime candidate for those improvements.
24   *
25   * <p>
26   *  It is important to realize that some objects are cheaper to simply allow
27   *  the garbage collector to take care of them.  Therefore, only pool objects
28   *  that are computationally expensive to create.  Prime candidates would be
29   *  Components, JDBC Connection objects, Socket connections, etc.
30   * </p>
31   * <p>
32   *  The interface is inspired by both the Mutex acquire/release and the
33   *  structure of the ThreadLocal object.  In fact, it would be trivial
34   *  to implement a "ThreadLocal" pool.
35   * </p>
36   *
37   * @author <a HREF="mailto:dev@avalon.apache.org">Avalon Development Team</a>
38   * @version CVS $Revision: 1.4 $ $Date: 2004/02/28 11:47:33 $
39   * @since 4.1.2
40   */
41  public interface Pool
42  {
43      /**
44       * Acquire an instance of the pooled object.
45       *
46       * @return the pooled Object instance
47       *
48       * @throws Exception if the Pool is not able to return an object.
49       */
50      Object   acquire() throws Exception  ;
51  
52      /**
53       * Release the instance of the pooled object.
54       *
55       * @param pooledObject  The pooled object to release to the pool.
56       */
57      void release( Object   pooledObject );
58  
59      /**
60       * Create a new instance of the object being pooled.
61       *
62       * @return the pooled Object instance
63       *
64       * @throws Exception if the instance cannot be created
65       */
66      Object   newInstance() throws Exception  ;
67  }
68
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