1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27 package org.apache.http.annotation;
28
29 import java.lang.annotation.Documented;
30 import java.lang.annotation.ElementType;
31 import java.lang.annotation.Retention;
32 import java.lang.annotation.RetentionPolicy;
33 import java.lang.annotation.Target;
34
35 /**
36 * The field or method to which this annotation is applied can only be accessed
37 * when holding a particular lock, which may be a built-in (synchronization) lock,
38 * or may be an explicit java.util.concurrent.Lock.
39 *
40 * The argument determines which lock guards the annotated field or method:
41 * <ul>
42 * <li>
43 * <code>this</code> : The intrinsic lock of the object in whose class the field is defined.
44 * </li>
45 * <li>
46 * <code>class-name.this</code> : For inner classes, it may be necessary to disambiguate 'this';
47 * the <em>class-name.this</em> designation allows you to specify which 'this' reference is intended
48 * </li>
49 * <li>
50 * <code>itself</code> : For reference fields only; the object to which the field refers.
51 * </li>
52 * <li>
53 * <code>field-name</code> : The lock object is referenced by the (instance or static) field
54 * specified by <em>field-name</em>.
55 * </li>
56 * <li>
57 * <code>class-name.field-name</code> : The lock object is reference by the static field specified
58 * by <em>class-name.field-name</em>.
59 * </li>
60 * <li>
61 * <code>method-name()</code> : The lock object is returned by calling the named nil-ary method.
62 * </li>
63 * <li>
64 * <code>class-name.class</code> : The Class object for the specified class should be used as the lock object.
65 * </li>
66 * <p>
67 * Based on code developed by Brian Goetz and Tim Peierls and concepts
68 * published in 'Java Concurrency in Practice' by Brian Goetz, Tim Peierls,
69 * Joshua Bloch, Joseph Bowbeer, David Holmes and Doug Lea.
70 */
71 @Documented
72 @Target({ElementType.FIELD, ElementType.METHOD})
73 @Retention(RetentionPolicy.CLASS) // The original version used RUNTIME
74 public @interface GuardedBy {
75 String value();
76 }