01: /*
02: * Copyright 2002,2004 The Apache Software Foundation.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
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:
23: /** A tag which conditionally evaluates its body based on some condition
24: *
25: * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
26: * @version $Revision: 155420 $
27: */
28: public class WhenTag extends TagSupport {
29:
30: /** The expression to evaluate. */
31: private Expression test;
32:
33: public WhenTag() {
34: }
35:
36: // Tag interface
37: //-------------------------------------------------------------------------
38: public void doTag(XMLOutput output) throws JellyTagException {
39: ChooseTag tag = (ChooseTag) findAncestorWithClass(ChooseTag.class);
40: if (tag == null) {
41: throw new JellyTagException(
42: "This tag must be enclosed inside a <choose> tag");
43: }
44: if (!tag.isBlockEvaluated() && test != null) {
45: if (test.evaluateAsBoolean(context)) {
46: tag.setBlockEvaluated(true);
47: invokeBody(output);
48: }
49: }
50: }
51:
52: // Properties
53: //-------------------------------------------------------------------------
54:
55: /** Sets the expression to evaluate. */
56: public void setTest(Expression test) {
57: this.test = test;
58: }
59:
60: }
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