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


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.AbstractComponent;
18 import org.apache.tapestry.IComponent;
19 import org.apache.tapestry.IMarkupWriter;
20 import org.apache.tapestry.IRequestCycle;
21
22 /**
23  * Renders the text and components wrapped by a {@link Block}component. [ <a
24  * HREF="../../../../../ComponentReference/RenderBlock.html">Component Reference </a>]
25  * <p>
26  * It is possible for an RenderBlock to obtain a Block from a page <em>other than</em> the render
27  * page. This works, even when the Block contains links, forms and form components. The action and
28  * direct services will create URLs that properly address this situation.
29  * <p>
30  * However, because the rendering page can't know ahead of time about these foreign Blocks,
31  * {@link org.apache.tapestry.event.PageBeginRenderListener} and
32  * {@link org.apache.tapestry.event.PageEndRenderListener} methods (for components and objects of the
33  * foreign page) via RenderBlock will <em>not</em> be executed. This specifically affects the
34  * methods of the {@link org.apache.tapestry.event.PageBeginRenderListener} and
35  * {@link org.apache.tapestry.event.PageEndRenderListener} interfaces.
36  * <p>
37  * Before rendering its {@link Block}, RenderBlock will set itself as the Block's inserter, and
38  * will reset the inserter after the {@link Block}is rendered. This gives the components contained
39  * in the {@link Block}access to its inserted environment via the RenderBlock. In particular this
40  * allows the contained components to access the informal parameters of the RenderBlock which
41  * effectively allows parameters to be passed to the components contained in a Block.
42  *
43  * @author Howard Lewis Ship
44  */
45
46 public abstract class RenderBlock extends AbstractComponent
47 {
48     /**
49      * If block is not null, then
50      * {@link Block#renderForComponent(IMarkupWriter, IRequestCycle, IComponent)} is invoked.
51      */
52
53     protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
54     {
55         Block block = getBlock();
56
57         if (block == null)
58             return;
59
60         block.renderForComponent(writer, cycle, this);
61     }
62
63     public abstract Block getBlock();
64
65 }
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