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.IMarkupWriter; 018 import org.apache.tapestry.IRender; 019 import org.apache.tapestry.IRequestCycle; 020 021 /** 022 * An implementation of IRender that renders a Block component. 023 * 024 * <p>The BlockRenderer allows the contents of a {@link Block} to be rendered 025 * via {@link IRender}. It can be used in cases when an {@link IRender} object is 026 * required as an argument or a binding to render a part of a Component. 027 * To provide a complicated view, it could be defined in a {@link Block} and then 028 * returned encapsulated in a BlockRenderer. 029 * 030 * <p>It is important to note that a special care has to be taken if 031 * the BlockRenderer is used within an inner class of a component or a page. 032 * In such a case the instance of the component that created the inner class 033 * may not be the currently active instance in the RequestCycle when the 034 * BlockRenderer is required. Thus, calling getComponent("blockName") to get the 035 * block component may return a Block component that is not initialized for this 036 * RequestCycle. 037 * 038 * <p>To avoid similar problems, the ComponentAddress class could be used in 039 * conjunction with BlockRenderer. 040 * Here is a quick example of how BlockRenderer could be used with ComponentAddress: 041 * <p> 042 * <code> 043 * <br>// Create a component address for the current component 044 * <br>final ComponentAddress address = new ComponentAddress(this); 045 * <br>return new SomeClass() { 046 * <br> IRender getRenderer(IRequestCycle cycle) { 047 * <br> MyComponent component = (MyComponent) address.findComponent(cycle); 048 * <br> // initialize variables in the component that will be used by the block here 049 * <br> return new BlockRenderer(component.getComponent("block")); 050 * <br> } 051 * <br>} 052 * </code> 053 * 054 * @author mindbridge 055 * @since 2.2 056 */ 057 public class BlockRenderer implements IRender 058 { 059 private Block m_objBlock; 060 061 /** 062 * Creates a new BlockRenderer that will render the content of the argument 063 * @param objBlock the Block to be rendered 064 */ 065 public BlockRenderer(Block objBlock) 066 { 067 m_objBlock = objBlock; 068 } 069 070 /** 071 * @see org.apache.tapestry.IRender#render(IMarkupWriter, IRequestCycle) 072 */ 073 public void render(IMarkupWriter writer, IRequestCycle cycle) 074 { 075 m_objBlock.renderBody(writer, cycle); 076 } 077 078 }