01: /*
02: * Copyright 2002,2004 The Apache Software Foundation.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
10: * Unless required by applicable law or agreed to in writing, software
11: * distributed under the License is distributed on an "AS IS" BASIS,
12: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13: * See the License for the specific language governing permissions and
14: * limitations under the License.
15: */
16: package org.apache.commons.jelly.expression;
17:
18: import org.apache.commons.jelly.JellyContext;
19:
20: /** <p><code>ConstantExpression</code> represents a constant expression.</p>
21: *
22: * <p> In other words, {@link #evaluate} returns a value independent of the context. </p>
23: *
24: * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
25: * @version $Revision: 155420 $
26: */
27: public class ConstantExpression extends ExpressionSupport {
28:
29: /** The value of this expression */
30: private Object value;
31:
32: /** Base constructor
33: */
34: public ConstantExpression() {
35: }
36:
37: /** Convenience constructor sets <code>value</code> property.
38: */
39: public ConstantExpression(Object value) {
40: this .value = value;
41: }
42:
43: public String toString() {
44: return super .toString() + "[value=" + value + "]";
45: }
46:
47: public String getExpressionText() {
48: return value == null ? "null" : value.toString();
49: }
50:
51: /**
52: * Evaluate expression against given context.
53: *
54: * @param context evaluate expression against this context
55: * @return current value of <code>value</code> property
56: */
57: public Object evaluate(JellyContext context) {
58: return value;
59: }
60:
61: /** Gets the constant value of this expression */
62: public Object getValue() {
63: return value;
64: }
65:
66: /** Sets the constant value of this expression */
67: public void setValue(Object value) {
68: this.value = value;
69: }
70: }
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