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.betwixt.expression;
18
19 /** <p><code>EmptyExpression</code> returns the same value as is passed in. </p>
20 *
21 * <p> See {@link #evaluate}. </p>
22 *
23 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
24 * @version $Revision: 438373 $
25 */
26 public class EmptyExpression implements Expression {
27
28 /** Don't need more than one <code>EmptyExpression</code>*/
29 private static final EmptyExpression singleton = new EmptyExpression();
30
31 /**
32 * Gets the singleton instance.
33 * @return the EmptyExpression singleton.
34 */
35 public static EmptyExpression getInstance() {
36 return singleton;
37 }
38
39 /** Should this be private?
40 */
41 public EmptyExpression() {
42 }
43
44 /** Return the bean we're evaluating.
45 * @see org.apache.commons.betwixt.expression.Expression
46 */
47 public Object evaluate(Context context) {
48 return context.getBean();
49 }
50
51 /** Do nothing
52 * @see org.apache.commons.betwixt.expression.Expression
53 */
54 public void update(Context context, String newValue) {
55 // do nothing
56 }
57
58 /**
59 * Return something useful for logging.
60 * @return short name for this class
61 */
62 public String toString() {
63 return "EmptyExpression";
64 }
65
66 }