1/*
2 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
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
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package com.sun.jndi.ldap.pool;
27
28import java.lang.ref.WeakReference;
29import 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 */
58class ConnectionsWeakRef extends WeakReference<ConnectionsRef> {
59
60    private final Connections conns;
61
62    ConnectionsWeakRef (ConnectionsRef connsRef,
63                        ReferenceQueue<? super ConnectionsRef> queue) {
64        super(connsRef, queue);
65        this.conns = connsRef.getConnections();
66    }
67
68    Connections getConnections() {
69        return conns;
70    }
71}
72