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


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
22
23 /**
24  * A tag which conditionally evaluates its body if
25  * none of its preceeding sibling {@link CaseTag <case>}
26  * tags have been evaluated.
27  *
28  * This tag must be contained within the body of some
29  * {@link SwitchTag <switch>} tag.
30  *
31  * @see SwitchTag
32  *
33  * @author Rodney Waldhoff
34  * @version $Revision: 155420 $ $Date: 2005-02-26 05:06:03 -0800 $
35  */
36 public class DefaultTag extends TagSupport {
37
38     public DefaultTag() {
39     }
40
41     // Tag interface
42 //-------------------------------------------------------------------------
43
44     public void setFallThru(boolean fallThru) {
45         this.fallThru = fallThru;
46     }
47
48     public void doTag(XMLOutput output) throws JellyTagException {
49         SwitchTag tag = (SwitchTag)findAncestorWithClass(SwitchTag.class);
50         if(null == tag) {
51             throw new JellyTagException("This tag must be enclosed inside a <switch> tag" );
52         }
53         if(tag.hasDefaultBeenEncountered()) {
54             throw new JellyTagException("Only one <default> tag is allowed per <switch>.");
55         }
56         tag.defaultEncountered();
57         if(tag.isFallingThru() || (!tag.hasSomeCaseMatched())) {
58             tag.caseMatched();
59             tag.setFallingThru(fallThru);
60             invokeBody(output);
61         }
62     }
63
64     // Attributes
65 //-------------------------------------------------------------------------
66 private boolean fallThru = false;
67
68 }
69
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