1 /*
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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4  *
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7  * published by the Free Software Foundation.  Oracle designates this
8  * particular file as subject to the "Classpath" exception as provided
9  * by Oracle in the LICENSE file that accompanied this code.
10  *
11  * This code is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
16  *
17  * You should have received a copy of the GNU General Public License version
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19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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24  */
25 
26 package com.sun.jndi.ldap.pool;
27 
28 import java.lang.ref.WeakReference;
29 import java.lang.ref.ReferenceQueue;
30 
31 /*
32  * This class defines a WeakReference to the ConnectionRef (the referent).
33  *
34  * The ConnectionRef enables to break the reference
35  * cycle between Connection, LdapClient, Connections and ConnectionDesc,
36  * shown in the figure below.
37  *
38  *        -------> Connections -----> ConnectionDesc
39  *        |              ^                  |
40  *        |              |                  |
41  *        |              |                  |
42  * ConnectionsRef    LdapClient <------------
43  *        ^              |   ^
44  *        :              |   |
45  *        :              v   |
46  * ConnectionsWeakRef  Connection
47  *
48  * The ConnectionsRef is for cleaning up the resources held by the
49  * Connection thread by making them available to the GC. The pool
50  * uses ConnectionRef to hold the pooled resources.
51  *
52  * This class in turn holds a WeakReference with a ReferenceQueue to the
53  * ConnectionRef to track when the ConnectionRef becomes ready
54  * for getting GC'ed. It extends from WeakReference in order to hold a
55  * reference to Connections used for closing (which in turn terminates
56  * the Connection thread) it by monitoring the ReferenceQueue.
57  */
58 class ConnectionsWeakRef extends WeakReference<ConnectionsRef> {
59 
60     private final Connections conns;
61 
ConnectionsWeakRef(ConnectionsRef connsRef, ReferenceQueue<? super ConnectionsRef> queue)62     ConnectionsWeakRef (ConnectionsRef connsRef,
63                         ReferenceQueue<? super ConnectionsRef> queue) {
64         super(connsRef, queue);
65         this.conns = connsRef.getConnections();
66     }
67 
getConnections()68     Connections getConnections() {
69         return conns;
70     }
71 }
72