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


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.tapestry.IMarkupWriter;
18 import org.apache.tapestry.IRender;
19 import org.apache.tapestry.IRequestCycle;
20
21 /**
22  * An implementation of IRender that renders a Block component.
23  *
24  * <p>The BlockRenderer allows the contents of a {@link Block} to be rendered
25  * via {@link IRender}. It can be used in cases when an {@link IRender} object is
26  * required as an argument or a binding to render a part of a Component.
27  * To provide a complicated view, it could be defined in a {@link Block} and then
28  * returned encapsulated in a BlockRenderer.
29  *
30  * <p>It is important to note that a special care has to be taken if
31  * the BlockRenderer is used within an inner class of a component or a page.
32  * In such a case the instance of the component that created the inner class
33  * may not be the currently active instance in the RequestCycle when the
34  * BlockRenderer is required. Thus, calling getComponent("blockName") to get the
35  * block component may return a Block component that is not initialized for this
36  * RequestCycle.
37  *
38  * <p>To avoid similar problems, the ComponentAddress class could be used in
39  * conjunction with BlockRenderer.
40  * Here is a quick example of how BlockRenderer could be used with ComponentAddress:
41  * <p>
42  * <code>
43  * <br>// Create a component address for the current component
44  * <br>final ComponentAddress address = new ComponentAddress(this);
45  * <br>return new SomeClass() {
46  * <br>&nbsp;&nbsp;IRender getRenderer(IRequestCycle cycle) {
47  * <br>&nbsp;&nbsp;&nbsp;&nbsp;MyComponent component = (MyComponent) address.findComponent(cycle);
48  * <br>&nbsp;&nbsp;&nbsp;&nbsp;// initialize variables in the component that will be used by the block here
49  * <br>&nbsp;&nbsp;&nbsp;&nbsp;return new BlockRenderer(component.getComponent("block"));
50  * <br>&nbsp;&nbsp;}
51  * <br>}
52  * </code>
53  *
54  * @author mindbridge
55  * @since 2.2
56  */
57 public class BlockRenderer implements IRender
58 {
59     private Block m_objBlock;
60
61     /**
62      * Creates a new BlockRenderer that will render the content of the argument
63      * @param objBlock the Block to be rendered
64      */
65     public BlockRenderer(Block objBlock)
66     {
67         m_objBlock = objBlock;
68     }
69
70     /**
71      * @see org.apache.tapestry.IRender#render(IMarkupWriter, IRequestCycle)
72      */
73     public void render(IMarkupWriter writer, IRequestCycle cycle)
74     {
75         m_objBlock.renderBody(writer, cycle);
76     }
77
78 }
79
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