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Java > Open Source Codes > org > apache > commons > jelly > tags > core > ExprTag


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.tags.core;
17
18 import org.apache.commons.jelly.JellyTagException;
19 import org.apache.commons.jelly.TagSupport;
20 import org.apache.commons.jelly.XMLOutput;
21 import org.apache.commons.jelly.expression.Expression;
22 import org.xml.sax.SAXException JavaDoc;
23
24 /** A tag which evaluates an expression
25   *
26   * @tag out
27   * @author <a HREF="mailto:jstrachan@apache.org">James Strachan</a>
28   * @version $Revision: 155420 $
29   */
30 public class ExprTag extends TagSupport {
31
32     /** The expression to evaluate. */
33     private Expression value;
34
35     public ExprTag() {
36     }
37
38     // Tag interface
39 //-------------------------------------------------------------------------
40 public void doTag(XMLOutput output) throws JellyTagException {
41         if (value != null) {
42             String JavaDoc text = value.evaluateAsString(context);
43             if (text != null) {
44
45                 try {
46                     output.write(text);
47                 }
48                 catch (SAXException JavaDoc e) {
49                     throw new JellyTagException("could not write the XMLOutput",e);
50                 }
51             }
52         }
53     }
54
55     // Properties
56 //-------------------------------------------------------------------------
57
58     /**
59      * Sets the Jexl expression to evaluate.
60      *
61      * @required true
62      */
63     public void setValue(Expression value) {
64         this.value = value;
65     }
66 }
67
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