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1   /*
2    * Copyright 2002,2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
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  }