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 }