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 015package org.apache.tapestry.components; 016 017import org.apache.hivemind.util.Defense; 018import org.apache.tapestry.AbstractComponent; 019import org.apache.tapestry.IComponent; 020import org.apache.tapestry.IMarkupWriter; 021import org.apache.tapestry.IRequestCycle; 022 023/** 024 * Prevents its contents from being rendered until triggered by an {@link RenderBlock} component. [<a 025 * href="../../../../../ComponentReference/Block.html">Component Reference</a>] 026 * <p> 027 * Block and {@link RenderBlock} are used to build a certain class of complicated component that 028 * can't be assembled using the normal wrapping containment. Such a super component would have two 029 * or more sections that need to be supplied by the containing page (or component). 030 * <p> 031 * Using Blocks, the blocks can be provided as parameters to the super component. 032 * <p> 033 * The invoker property gives the components inside the block access to the component (typically an 034 * {@link RenderBlock}) that rendered the block. More often, the {@link #getParameter(String)} 035 * method is used to get parameters <em>of the invoking component</em>. 036 * 037 * @author Howard Lewis Ship 038 * @since 0.2.9 039 */ 040 041public abstract class Block extends AbstractComponent 042{ 043 private IComponent _invoker; 044 045 /** 046 * Provides access to the invoking component's parameters. 047 * 048 * @since 4.0 049 */ 050 051 public Object getParameter(String name) 052 { 053 return _invoker.getBinding(name).getObject(); 054 } 055 056 public void renderForComponent(IMarkupWriter writer, IRequestCycle cycle, IComponent invoker) 057 { 058 Defense.notNull(invoker, "invoker"); 059 060 IComponent oldInvoker = _invoker; 061 062 try 063 { 064 _invoker = invoker; 065 renderBody(writer, cycle); 066 } 067 finally 068 { 069 _invoker = oldInvoker; 070 071 } 072 } 073 074 /** 075 * Does nothing; the idea of a Block is to defer the rendering of the body of the block until an 076 * {@link RenderBlock} forces it out. 077 */ 078 079 protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle) 080 { 081 // Nothing! 082 } 083 084 /** 085 * @deprecated Use {@link #getInvoker()} instead. 086 */ 087 public IComponent getInserter() 088 { 089 return _invoker; 090 } 091 092 /** 093 * Returns the object which invoked this Block's 094 * {@link #renderForComponent(IMarkupWriter, IRequestCycle, IComponent)} method. This is often 095 * used to access the informal parameters of a {@link RenderBlock} component. 096 * 097 * @since 4.0 098 */ 099 public IComponent getInvoker() 100 { 101 return _invoker; 102 } 103 104 /** 105 * Used for testing only. 106 * 107 * @since 4.0 108 */ 109 110 void setInvoker(IComponent invoker) 111 { 112 _invoker = invoker; 113 } 114}