View Javadoc

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  }