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1   /*
2    * Copyright 2001-2004 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.betwixt.expression;
17  
18  /*** <p><code>StringExpression</code> returns the current context object as a string.</p>
19    *
20    * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
21    * @version $Revision: 155402 $
22    */
23  public class StringExpression implements Expression {
24      
25      /*** We only need only <code>StringExpression</code> */
26      private static final StringExpression singleton = new StringExpression();
27      
28      /*** 
29       * Gets the singleton 
30       * @return the singleton <code>StringExpression</code> instance
31       */
32      public static StringExpression getInstance() {
33          return singleton;
34      }
35      
36      /*** Base constructor. Should this be private? */
37      public StringExpression() {
38      }
39      
40      /*** Return the context bean as a string
41        *
42        * @param context evaluate expression against this context
43        * @return the <code>toString()</code> representation of the context bean
44        */
45      public Object evaluate(Context context) {
46          Object value = context.getBean();
47          if ( value != null ) {
48              return value.toString();
49          }
50          return null;
51      }
52      
53      /***
54       * Do nothing 
55       * @see org.apache.commons.betwixt.expression.Expression
56       */
57      public void update(Context context, String newValue) {
58          // do nothing
59      }
60      
61      /***
62       * Returns something useful for logging.
63       * @return the (short) class name
64       */
65      public String toString() {
66          return "StringExpression";
67      }
68  
69  }