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.html; 016 017import org.apache.tapestry.AbstractComponent; 018import org.apache.tapestry.IAsset; 019import org.apache.tapestry.IMarkupWriter; 020import org.apache.tapestry.IRequestCycle; 021import org.apache.tapestry.Tapestry; 022 023/** 024 * Used to insert an image. To create a rollover image, use the {@link Rollover} class, which 025 * integrates a link with the image assets used with the button. [<a 026 * href="../../../../../ComponentReference/Image.html">Component Reference</a>] 027 * 028 * @author Howard Lewis Ship 029 */ 030 031public abstract class Image extends AbstractComponent 032{ 033 /** 034 * Renders the <img> element. 035 */ 036 037 protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle) 038 { 039 // Doesn't contain a body so no need to do anything on rewind (assumes no 040 // sideffects to accessor methods via bindings). 041 042 if (cycle.isRewinding()) 043 return; 044 045 IAsset imageAsset = getImage(); 046 047 if (imageAsset == null) 048 throw Tapestry.createRequiredParameterException(this, "image"); 049 050 String imageURL = imageAsset.buildURL(); 051 052 writer.beginEmpty("img"); 053 054 writer.attribute("src", imageURL); 055 056 renderInformalParameters(writer, cycle); 057 058 writer.closeTag(); 059 } 060 061 public abstract IAsset getImage(); 062}