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Java > Open Source Codes > org > apache > cocoon > taglib > IterationTag


1 /*
2  * Copyright 1999-2004 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.cocoon.taglib;
17
18 import org.xml.sax.SAXException JavaDoc;
19
20 /**
21  * The IterationTag interface extends Tag by defining one additional
22  * method that controls the reevaluation of its body.
23  *
24  * <p> A tag handler that implements IterationTag is treated as one that
25  * implements Tag regarding the doStartTag() and doEndTag() methods.
26  * IterationTag provides a new method: <code>doAfterBody()</code>.
27  *
28  * <p> The doAfterBody() method is invoked after every body evaluation
29  * to control whether the body will be reevaluated or not. If doAfterBody()
30  * returns IterationTag.EVAL_BODY_AGAIN, then the body will be reevaluated.
31  * If doAfterBody() returns Tag.SKIP_BODY, then the body will be skipped
32  * and doEndTag() will be evaluated instead.
33  *
34  * @author <a HREF="mailto:volker.schmitt@basf-it-services.com">Volker Schmitt</a>
35  * @version CVS $Id: IterationTag.java 30932 2004-07-29 17:35:38Z vgritsenko $
36  */
37 public interface IterationTag extends Tag {
38
39     /**
40      * Request the reevaluation of some body.
41      * Returned from doAfterBody.
42      */
43     public final static int EVAL_BODY_AGAIN = 2;
44
45     /**
46      * Process body (re)evaluation. This method is invoked by the
47      * Taglib implementation object after every evaluation of
48      * the body into the BodyEvaluation object. The method is
49      * not invoked if there is no body evaluation.
50      *
51      * <p>
52      * If doAfterBody returns EVAL_BODY_AGAIN, a new evaluation of the
53      * body will happen (followed by another invocation of doAfterBody).
54      * If doAfterBody returns SKIP_BODY no more body evaluations will
55      * occur and then doEndTag will be invoked.
56      *
57      * <p>
58      * The method re-invocations may be lead to different actions because
59      * there might have been some changes to shared state, or because
60      * of external computation.
61      *
62      * @return whether additional evaluations of the body are desired
63      * @throws SAXException
64      */
65     int doAfterBody() throws SAXException JavaDoc;
66 }
67
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