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 &lt;img&gt; 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}