001 // Copyright 2004, 2005 The Apache Software Foundation 002 // 003 // Licensed under the Apache License, Version 2.0 (the "License"); 004 // you may not use this file except in compliance with the License. 005 // You may obtain a copy of the License at 006 // 007 // http://www.apache.org/licenses/LICENSE-2.0 008 // 009 // Unless required by applicable law or agreed to in writing, software 010 // distributed under the License is distributed on an "AS IS" BASIS, 011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 012 // See the License for the specific language governing permissions and 013 // limitations under the License. 014 015 package org.apache.tapestry.components; 016 017 import org.apache.tapestry.AbstractComponent; 018 import org.apache.tapestry.IMarkupWriter; 019 import org.apache.tapestry.IRequestCycle; 020 021 /** 022 * Renders the text and components wrapped by a {@link Block}component. [ <a 023 * href="../../../../../ComponentReference/RenderBlock.html">Component Reference </a>] 024 * <p> 025 * It is possible for an RenderBlock to obtain a Block from a page <em>other than</em> the render 026 * page. This works, even when the Block contains links, forms and form components. The action and 027 * direct services will create URLs that properly address this situation. 028 * <p> 029 * However, because the rendering page can't know ahead of time about these foreign Blocks, 030 * {@link org.apache.tapestry.event.PageBeginRenderListener} and 031 * {@link org.apache.tapestry.event.PageEndRenderListener} methods (for components and objects of the 032 * foreign page) via RenderBlock will <em>not</em> be executed. This specifically affects the 033 * methods of the {@link org.apache.tapestry.event.PageBeginRenderListener} and 034 * {@link org.apache.tapestry.event.PageEndRenderListener} interfaces. 035 * <p> 036 * Before rendering its {@link Block}, RenderBlock will set itself as the Block's inserter, and 037 * will reset the inserter after the {@link Block}is rendered. This gives the components contained 038 * in the {@link Block}access to its inserted environment via the RenderBlock. In particular this 039 * allows the contained components to access the informal parameters of the RenderBlock which 040 * effectively allows parameters to be passed to the components contained in a Block. 041 * 042 * @author Howard Lewis Ship 043 */ 044 045 public abstract class RenderBlock extends AbstractComponent 046 { 047 /** 048 * If block is not null, then 049 * {@link Block#renderForComponent(IMarkupWriter, IRequestCycle, IComponent)} is invoked. 050 */ 051 052 protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle) 053 { 054 Block block = getBlock(); 055 056 if (block == null) 057 return; 058 059 block.renderForComponent(writer, cycle, this); 060 } 061 062 public abstract Block getBlock(); 063 064 }