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  
17  package org.apache.commons.jelly.tags.core;
18  
19  import org.apache.commons.jelly.JellyTagException;
20  import org.apache.commons.jelly.MissingAttributeException;
21  import org.apache.commons.jelly.TagSupport;
22  import org.apache.commons.jelly.XMLOutput;
23  import org.apache.commons.jelly.expression.Expression;
24  import org.apache.commons.jelly.impl.BreakException;
25  import org.apache.commons.logging.Log;
26  import org.apache.commons.logging.LogFactory;
27  
28  /***
29   * A tag which performs an iteration while the result of an expression is true.
30   *
31   * @author <a href="mailto:eric@ericalexander.net">Eric Alexander</a>
32   * @author dIon Gillard
33   * @version $Revision: 155420 $
34   */
35  public class WhileTag extends TagSupport {
36  
37      /*** The Log to which logging calls will be made. */
38      private static final Log log = LogFactory.getLog(WhileTag.class);
39  
40      /*** The expression to use to determine if the while should continue */
41      private Expression test;
42  
43      /***
44       * Create a new while tag
45       */
46      public WhileTag() {
47      }
48  
49      /***
50       * Tag interface
51       * @param output destination for xml output
52       * @throws MissingAttributeException when the test attribute is missing
53       * @throws Exception for anything else
54       */
55      public void doTag(XMLOutput output) throws MissingAttributeException, JellyTagException {
56          if (test != null) {
57              try {
58                  while (test.evaluateAsBoolean(getContext())) {
59                      if (log.isDebugEnabled()) {
60                          log.debug("evaluated to true! gonna keep on chuggin!");
61                      }
62                      invokeBody(output);
63                  }
64              }
65              catch (BreakException e) {
66                  if (log.isDebugEnabled()) {
67                      log.debug("loop terminated by break: " + e, e);
68                  }
69              }
70          }
71          else {
72              throw new MissingAttributeException("test");
73          }
74      }
75  
76      // Properties
77      //-------------------------------------------------------------------------
78  
79      /***
80       * Setter for the expression
81       * @param e the expression to test
82       */
83      public void setTest(Expression e) {
84          this.test = e;
85      }
86  }
87