View Javadoc

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