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


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.MissingAttributeException;
20 import org.apache.commons.jelly.TagSupport;
21 import org.apache.commons.jelly.XMLOutput;
22 import org.apache.commons.jelly.expression.Expression;
23
24 /** A tag which conditionally evaluates its body based on some condition
25   *
26   * @author <a HREF="mailto:jstrachan@apache.org">James Strachan</a>
27   * @version $Revision: 155420 $
28   */
29 public class IfTag extends TagSupport {
30
31     /** The expression to evaluate. */
32     private Expression test;
33
34     public IfTag() {
35     }
36
37     // Tag interface
38 //-------------------------------------------------------------------------
39 public void doTag(XMLOutput output) throws MissingAttributeException, JellyTagException {
40         if (test != null) {
41             if (test.evaluateAsBoolean(context)) {
42                 invokeBody(output);
43             }
44         }
45         else {
46             throw new MissingAttributeException( "test" );
47         }
48
49     }
50
51     // Properties
52 //-------------------------------------------------------------------------
53 /** Sets the Jelly expression to evaluate. If this returns true, the body of
54      * the tag is evaluated
55      *
56      * @param test the Jelly expression to evaluate
57      */
58     public void setTest(Expression test) {
59         this.test = test;
60     }
61 }
62
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