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Java > Open Source Codes > org > apache > tapestry > components > Conditional


1 // Copyright 2004, 2005 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry.components;
16
17 import org.apache.hivemind.HiveMind;
18 import org.apache.tapestry.AbstractComponent;
19 import org.apache.tapestry.IMarkupWriter;
20 import org.apache.tapestry.IRequestCycle;
21
22 /**
23  * A conditional element on a page which will render its wrapped elements zero or one times. [ <a
24  * HREF="../../../../../ComponentReference/Conditional.html">Component Reference </a>]
25  *
26  * @author Howard Lewis Ship, David Solis
27  */
28
29 public abstract class Conditional extends AbstractComponent
30 {
31     /**
32      * Renders its wrapped components only if the condition is true (technically, if condition
33      * matches invert). Additionally, if element is specified, can emulate that HTML element if
34      * condition is met
35      */
36
37     protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
38     {
39         if (evaluateCondition())
40         {
41             String JavaDoc element = getElement();
42
43             boolean render = !cycle.isRewinding() && HiveMind.isNonBlank(element);
44
45             if (render)
46             {
47                 writer.begin(element);
48                 renderInformalParameters(writer, cycle);
49             }
50
51             renderBody(writer, cycle);
52
53             if (render)
54                 writer.end(element);
55         }
56     }
57
58     protected boolean evaluateCondition()
59     {
60         return getCondition() != getInvert();
61     }
62
63     public abstract boolean getCondition();
64
65     public abstract boolean getInvert();
66
67     public abstract String JavaDoc getElement();
68 }
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