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