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Java > Open Source Codes > org > apache > commons > chain > Context


1 /*
2  * Copyright 2003-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.chain;
17
18
19 import java.util.Map JavaDoc;
20
21
22 /**
23  * <p>A {@link Context} represents the state information that is
24  * accessed and manipulated by the execution of a {@link Command} or a
25  * {@link Chain}. Specialized implementations of {@link Context} will
26  * typically add JavaBeans properties that contain typesafe accessors
27  * to information that is relevant to a particular use case for this
28  * context, and/or add operations that affect the state information
29  * that is saved in the context.</p>
30  *
31  * <p>Implementations of {@link Context} must also implement all of the
32  * required and optional contracts of the <code>java.util.Map</code>
33  * interface.</p>
34  *
35  * <p>It is strongly recommended, but not required, that JavaBeans
36  * properties added to a particular {@link Context} implementation exhibit
37  * <em>Attribute-Property Transparency</em>. In other words,
38  * a value stored via a call to <code>setFoo(value)</code> should be visible
39  * by calling <code>get("foo")</code>, and a value stored
40  * via a call to <code>put("foo", value)</code> should be
41  * visible by calling <code>getFoo()</code>. If your {@link Context}
42  * implementation class exhibits this featue, it becomes easier to reuse the
43  * implementation in multiple environments, without the need to cast to a
44  * particular implementation class in order to access the property getter
45  * and setter methods.</p>
46  *
47  * <p>To protect applications from evolution of this interface, specialized
48  * implementations of {@link Context} should generally be created by extending
49  * the provided base class ({@link org.apache.commons.chain.impl.ContextBase})
50  * rather than directly implementing this interface.</p>
51  *
52  * <p>Applications should <strong>NOT</strong> assume that
53  * {@link Context} implementations, or the values stored in its
54  * attributes, may be accessed from multiple threads
55  * simultaneously unless this is explicitly documented for a particular
56  * implementation.</p>
57  *
58  * @author Craig R. McClanahan
59  * @version $Revision: 1.6 $ $Date: 2004/02/25 00:01:07 $
60  */
61
62 public interface Context extends Map JavaDoc {
63
64
65 }
66
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