1 /**
2 * This file Copyright (c) 2003-2011 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.cms.taglibs;
35
36 import javax.servlet.jsp.JspException;
37 import javax.servlet.jsp.JspTagException;
38
39 /**
40 * Base class for implementing conditional tags (e.g. {@link IfEmpty}). Subclasses need to implement the {@link BaseConditionalContentTag#condition()} method.
41 * @author philipp
42 * @version $Id: BaseConditionalContentTag.java 41137 2011-01-06 18:19:25Z gjoseph $
43 *
44 */
45 public abstract class BaseConditionalContentTag extends BaseContentTag {
46
47 /**
48 * <p>Subclasses implement this method to compute the boolean result
49 * of the conditional action. This method is invoked once per tag invocation
50 * by <tt>doStartTag()</tt>.
51 *
52 * @return a boolean representing the condition that a particular subclass
53 * uses to drive its conditional logic.
54 */
55 protected abstract boolean condition() throws JspTagException;
56
57 /**
58 * Includes its body if <tt>condition()</tt> evaluates to true.
59 */
60 public int doStartTag() throws JspException {
61
62 // execute our condition() method once per invocation
63 boolean result = condition();
64
65 // handle conditional behavior
66 if (result)
67 return EVAL_BODY_INCLUDE;
68 else
69 return SKIP_BODY;
70 }
71
72 }