01: /*
02: * Licensed to the Apache Software Foundation (ASF) under one or more
03: * contributor license agreements. See the NOTICE file distributed with
04: * this work for additional information regarding copyright ownership.
05: * The ASF licenses this file to You under the Apache License, Version 2.0
06: * (the "License"); you may not use this file except in compliance with
07: * the License. You may obtain a copy of the License at
08: *
09: * 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: }
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