/hudson-core/src/main/java/hudson/CopyOnWrite.java

 1/*
 2 * The MIT License
 3 * 
 4 * Copyright (c) 2004-2009, Sun Microsystems, Inc., Kohsuke Kawaguchi
 5 * 
 6 * Permission is hereby granted, free of charge, to any person obtaining a copy
 7 * of this software and associated documentation files (the "Software"), to deal
 8 * in the Software without restriction, including without limitation the rights
 9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 * 
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
15 * 
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22 * THE SOFTWARE.
23 */
24package hudson;
25
26import java.lang.annotation.Documented;
27import static java.lang.annotation.ElementType.FIELD;
28import java.lang.annotation.Retention;
29import static java.lang.annotation.RetentionPolicy.SOURCE;
30import java.lang.annotation.Target;
31
32/**
33 * Represents fields that are protected for concurrency by the copy-on-write semantics.
34 *
35 * <p>
36 * Fields marked by this annotation always holds on to an immutable collection.
37 * A change to the collection must be done by first creating a new collection
38 * object, making changes, then replacing the reference atomically.
39 *
40 * <p>
41 * This allows code to access the field without synchronization, and
42 * greatly reduces the risk of dead-lock bugs.
43 *
44 * <p>
45 * The field marked with this annotation usually needs to be marked as
46 * <tt>volatile</tt>.
47 *
48 * @author Kohsuke Kawaguchi
49 */
50@Retention(SOURCE)
51@Documented
52@Target(FIELD)
53public @interface CopyOnWrite {
54}