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Java > Open Source Codes > org > apache > tapestry > contrib > components > When


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.contrib.components;
16
17 import org.apache.hivemind.ApplicationRuntimeException;
18 import org.apache.tapestry.IMarkupWriter;
19 import org.apache.tapestry.IRequestCycle;
20 import org.apache.tapestry.Tapestry;
21 import org.apache.tapestry.components.Conditional;
22
23 /**
24  * Represents an alternative whithin a {@link Choose} component.
25  * The default alternative is described by the Otherwise component.
26  *
27  * [<a HREF="../../../../../../ComponentReference/contrib.When.html">Component Reference</a>]
28  *
29  * @author David Solis
30  *
31  **/
32 public abstract class When extends Conditional
33 {
34     /** Parent of this component. */
35
36     private Choose _choose;
37
38     /**
39      * Renders its wrapped components only if the condition is true and its parent {@link Choose}
40      * allows it. In addition, if element is specified, can emulate that HTML element.
41      *
42      **/
43
44     protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
45     {
46         Choose choose = getChoose();
47
48         if (choose == null)
49             throw new ApplicationRuntimeException(
50                 Tapestry.getMessage("When.must-be-contained-by-choose"),
51                 this,
52                 null,
53                 null);
54
55         if (!choose.isConditionMet() && getCondition())
56         {
57             choose.setConditionMet(true);
58             super.renderComponent(writer, cycle);
59         }
60     }
61
62     protected boolean evaluateCondition()
63     {
64         return true;
65     }
66
67     public boolean getInvert()
68     {
69         // This component doesn't require invert parameter.
70 return false;
71     }
72
73     /**
74      * @return Choose
75      */
76     public Choose getChoose()
77     {
78         return _choose;
79     }
80
81     /**
82      * Sets the choose.
83      * @param value The choose to set
84      */
85     public void setChoose(Choose value)
86     {
87         _choose = value;
88     }
89
90 }
91
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