1 /*
2 * Copyright (c) 1997, 2017, 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
26 package com.sun.xml.internal.ws.util;
27
28 import com.sun.xml.internal.ws.api.pipe.Tube;
29 import com.sun.xml.internal.ws.api.pipe.TubeCloner;
30
31 import javax.xml.bind.JAXBContext;
32 import javax.xml.bind.JAXBException;
33
34 import java.util.concurrent.ConcurrentLinkedQueue;
35 import java.lang.ref.SoftReference;
36
37
38 /**
39 * General-purpose object pool.
40 *
41 * <p>
42 * In many parts of the runtime, we need to pool instances of objects that
43 * are expensive to create (such as JAXB objects, StAX parsers, {@link Tube} instances.)
44 *
45 * <p>
46 * This class provides a default implementation of such a pool.
47 *
48 * TODO: improve the implementation
49 *
50 * @author Kohsuke Kawaguchi
51 */
52 public abstract class Pool<T> {
53
54 // volatile since multiple threads may access queue reference
55 private volatile SoftReference<ConcurrentLinkedQueue<T>> queue;
56
57 /**
58 * Gets a new object from the pool.
59 *
60 * <p>
61 * If no object is available in the pool, this method creates a new one.
62 *
63 * @return
64 * always non-null.
65 */
66 public final T take() {
67 T t = getQueue().poll();
68 if(t==null)
69 return create();
70 return t;
71 }
72
73 private ConcurrentLinkedQueue<T> getQueue() {
74 SoftReference<ConcurrentLinkedQueue<T>> q = queue;
75 if (q != null) {
76 ConcurrentLinkedQueue<T> d = q.get();
77 if (d != null)
78 return d;
79 }
80
81 // overwrite the queue
82 ConcurrentLinkedQueue<T> d = new ConcurrentLinkedQueue<T>();
83 queue = new SoftReference<ConcurrentLinkedQueue<T>>(d);
84
85 return d;
86 }
87
88 /**
89 * Returns an object back to the pool.
90 */
91 public final void recycle(T t) {
92 getQueue().offer(t);
93 }
94
95 /**
96 * Creates a new instance of object.
97 *
98 * <p>
99 * This method is used when someone wants to
100 * {@link #take() take} an object from an empty pool.
101 *
102 * <p>
103 * Also note that multiple threads may call this method
104 * concurrently.
105 */
106 protected abstract T create();
107
108
109 /**
110 * JAXB {@link javax.xml.bind.Marshaller} pool.
111 */
112 public static final class Marshaller extends Pool<javax.xml.bind.Marshaller> {
113 private final JAXBContext context;
114
115 public Marshaller(JAXBContext context) {
116 this.context = context;
117 }
118
119 @Override
120 protected javax.xml.bind.Marshaller create() {
121 try {
122 return context.createMarshaller();
123 } catch (JAXBException e) {
124 // impossible
125 throw new AssertionError(e);
126 }
127 }
128 }
129
130 /**
131 * JAXB {@link javax.xml.bind.Marshaller} pool.
132 */
133 public static final class Unmarshaller extends Pool<javax.xml.bind.Unmarshaller> {
134 private final JAXBContext context;
135
136 public Unmarshaller(JAXBContext context) {
137 this.context = context;
138 }
139
140 @Override
141 protected javax.xml.bind.Unmarshaller create() {
142 try {
143 return context.createUnmarshaller();
144 } catch (JAXBException e) {
145 // impossible
146 throw new AssertionError(e);
147 }
148 }
149 }
150
151 /**
152 * {@link Tube} pool.
153 */
154 public static final class TubePool extends Pool<Tube> {
155 private final Tube master;
156
157 public TubePool(Tube master) {
158 this.master = master;
159 recycle(master); // we'll use master as a part of the pool, too.
160 }
161
162 @Override
163 protected Tube create() {
164 return TubeCloner.clone(master);
165 }
166
167 /**
168 *
169 * @return master tubeline from pool
170 * @deprecated Expected to be used in rare cases where access to master
171 * tubeline is required and safe, such as Stub.close()."
172 */
173 @Deprecated()
174 public final Tube takeMaster() {
175 return master;
176 }
177
178 }
179 }