1 /*
2 * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/expression/ConstantExpression.java,v 1.2 2002/07/01 18:53:52 rdonkin Exp $
3 * $Revision: 1.2 $
4 * $Date: 2002/07/01 18:53:52 $
5 *
6 * ====================================================================
7 *
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 1999-2002 The Apache Software Foundation. All rights
11 * reserved.
12 *
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14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
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22 * the documentation and/or other materials provided with the
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26 * any, must include the following acknowlegement:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowlegement may appear in the software itself,
30 * if and wherever such third-party acknowlegements normally appear.
31 *
32 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
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41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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54 *
55 * This software consists of voluntary contributions made by many
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59 *
60 * $Id: ConstantExpression.java,v 1.2 2002/07/01 18:53:52 rdonkin Exp $
61 */
62 package org.apache.commons.betwixt.expression;
63
64 /*** <p><code>ConstantExpression</code> represents a constant expression.</p>
65 *
66 * <p> In other words, {@link #evaluate} returns a value independent of the context. </p>
67 *
68 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
69 * @version $Revision: 1.2 $
70 */
71 public class ConstantExpression implements Expression {
72
73 /*** The value of this expression */
74 private Object value;
75
76 /*** Base constructor
77 */
78 public ConstantExpression() {
79 }
80
81 /*** Convenience constructor sets <code>value</code> property.
82 */
83 public ConstantExpression(Object value) {
84 this.value = value;
85 }
86
87 /***
88 * Evaluate expression against given context.
89 *
90 * @param context evaluate expression against this context
91 * @return current value of <code>value</code> property
92 */
93 public Object evaluate(Context context) {
94 return value;
95 }
96
97 public void update(Context context, String newValue) {
98 // do nothing
99 }
100
101 /*** Gets the constant value of this expression */
102 public Object getValue() {
103 return value;
104 }
105
106 /*** Sets the constant value of this expression */
107 public void setValue(Object value) {
108 this.value = value;
109 }
110
111 public String toString() {
112 return "ConstantExpression [value=" + value + "]";
113 }
114 }
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