1 /*
2 * $Header: /home/cvs/jakarta-commons/betwixt/src/java/org/apache/commons/betwixt/expression/EmptyExpression.java,v 1.2 2002/07/01 18:54:38 rdonkin Exp $
3 * $Revision: 1.2 $
4 * $Date: 2002/07/01 18:54:38 $
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 *
13 * Redistribution and use in source and binary forms, with or without
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 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution, if
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
33 * Foundation" must not be used to endorse or promote products derived
34 * from this software without prior written permission. For written
35 * permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache"
38 * nor may "Apache" appear in their names without prior written
39 * permission of the Apache Group.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>;.
59 *
60 * $Id: EmptyExpression.java,v 1.2 2002/07/01 18:54:38 rdonkin Exp $
61 */
62 package org.apache.commons.betwixt.expression;
63
64 /*** <p><code>EmptyExpression</code> returns the same value as is passed in. </p>
65 *
66 * <p> See {@link #evaluate}. </p>
67 *
68 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
69 * @version $Revision: 1.2 $
70 */
71 public class EmptyExpression implements Expression {
72
73 /*** Don't need more than one <code>EmptyExpression</code>*/
74 private static final EmptyExpression singleton = new EmptyExpression();
75
76 /*** Return the <code>EmptyExpression</code> singleton.
77 */
78 public static EmptyExpression getInstance() {
79 return singleton;
80 }
81
82 /*** Should this be private?
83 */
84 public EmptyExpression() {
85 }
86
87 /*** Return the bean we're evaluating.
88 */
89 public Object evaluate(Context context) {
90 return context.getBean();
91 }
92
93 public void update(Context context, String newValue) {
94 // do nothing
95 }
96
97 public String toString() {
98 return "EmptyExpression";
99 }
100
101 }
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