FakeSerializableArrayList


1   /**
2   *   Library name : Primrose - A Java Database Connection Pool.
3   *   Published by Ben Keeping, http://primrose.org.uk .
4   *   Copyright (C) 2004 Ben Keeping, primrose.org.uk
5   *   Email: Use "Contact Us Form" on website
6   *
7   *   This library is free software; you can redistribute it and/or
8   *   modify it under the terms of the GNU Lesser General Public
9   *   License as published by the Free Software Foundation; either
10  *   version 2.1 of the License, or (at your option) any later version.
11  *
12  *   This library 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 library; if not, write to the Free Software
19  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20  */
21  
22  package uk.org.primrose.vendor.jboss.jndi;
23  
24  import java.util.ArrayList  ;
25  import java.io.Serializable  ;
26  import org.jboss.naming.NonSerializableFactory;
27  
28  /**
29  *   This comment is on all of the vendor.jboss package classes, because the classes are
30  *   so interlinked. It documents how we bind primrose under JBoss.<p>
31  *   JBoss has two JNDI trees.
32  *   <ul>
33  *   <li>A serializable object tree.
34  *   <li>A non-serializable object tree.
35  *   </ul>
36  *   Primrose's core jmx objects (Queue, PoolController) cannot be bound under the serializable tree
37  *   because JBoss checks <i>on binding</i> whether the objects can be serialized. Because the Queue objects
38  *   contain Connection objects, this will always fail.<p>
39  *   So how do we get around this ?!<br>
40  *   First, the MasterPoolDataSourceFactory (deployed via the SAR) initializes the pool, and binds
41  *   the Queue objects, and the PoolController object under the non-serializable tree.<p>
42  *   Then all the pool DataSource objects, created via the PoolDataSourceFactory's (via BindPrimrose)
43  *   are all bound under the non-serializable tree.<br>
44  *   Get a list of the pools bound by PoolController,
45  *   and then for each one, let the PoolDataSourceFactory object
46  *   create our DatSource objects, which we will bind under the non-serializable tree.
47  *   Also bind our 'fake' DataSource objects under the normal JNDI tree
48  *   so they can be bound, and access the real non-serializable objects at runtime
49  *   for extracting client connections.<p>
50  *
51  *   When client code looks up our fake DataSource object (unbeknown to them obviously), and calls
52  *   the getConnection() method, our fake object gets a ref to the real DataSource from the non-serializable
53  *   JNDI tree, and extracts the Connection for the client.<p>
54  *
55  *   Why does this work ? <br>
56  *   The serializable JNDI tree only checks for serializablity at the point of binding - not when you
57  *   do lookup() calls - so as long as we can bind our fake DataSources at the primrose initialization
58  *   point, it works.
59  */
60  public class FakeSerializableArrayList implements Serializable   {
61      private String   name = "";
62  
63      /**
64      *   Default constructor to conform with Serialization protocol. Not used.
65      */
66      public FakeSerializableArrayList() {}
67  
68      /**
69      *   Construct the object with the name that the real JNDI resource is bound under.
70      */
71      public FakeSerializableArrayList(String   name) {
72          this.name = name;
73      }
74  
75      /**
76      *   Called from PoolDataSource.<br>
77      *   When the JNDI call is made to obtain the list of bound Queue objects,
78      *   it is checked whether the object is an instanceof FakeSerializableArrayList.<br>
79      *   If it is, this initialize() method is called to obtain the real ArrayList.
80      */
81      public ArrayList   initialize() {
82          ArrayList   faked = (ArrayList  )NonSerializableFactory.lookup(name);
83          return faked;
84      }
85  }
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