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.contrib.link;
016
017import org.apache.hivemind.ApplicationRuntimeException;
018import org.apache.tapestry.IMarkupWriter;
019import org.apache.tapestry.IRequestCycle;
020import org.apache.tapestry.Tapestry;
021import org.apache.tapestry.components.ILinkComponent;
022import org.apache.tapestry.engine.ILink;
023import org.apache.tapestry.link.ILinkRenderer;
024
025/**
026 * An {@link ILinkRenderer} implementation that generates an HTML button.
027 * This is particularly useful for implementing cancel buttons.
028 * 
029 * @author Paul Ferraro
030 * @since 4.0
031 */
032public class ButtonLinkRenderer implements ILinkRenderer
033{
034    public static final ILinkRenderer SHARED_INSTANCE = new ButtonLinkRenderer();
035
036    /**
037     * @see org.apache.tapestry.link.ILinkRenderer#renderLink(org.apache.tapestry.IMarkupWriter,
038     *      org.apache.tapestry.IRequestCycle, org.apache.tapestry.components.ILinkComponent)
039     */
040    public void renderLink(IMarkupWriter writer, IRequestCycle cycle, ILinkComponent component)
041    {
042        if (cycle.getAttribute(Tapestry.LINK_COMPONENT_ATTRIBUTE_NAME) != null)
043        {
044            String message = Tapestry.getMessage("AbstractLinkComponent.no-nesting");
045            throw new ApplicationRuntimeException(message, component, null, null);
046        }
047
048        cycle.setAttribute(Tapestry.LINK_COMPONENT_ATTRIBUTE_NAME, component);
049
050        ILink link = component.getLink(cycle);
051
052        writer.begin("button");
053        writer.attribute("type", "button");
054
055        if (component.isDisabled())
056        {
057            writer.attribute("disabled", "disabled");
058        }
059
060        if (!cycle.isRewinding()) {
061                String url = link.getURL(component.getAnchor(), true);
062                String target = component.getTarget();
063                String onclick = (target == null) ? getScript(url) : getScript(url, target);
064        
065                writer.attribute("onclick", onclick);
066        }
067        
068        component.renderAdditionalAttributes(writer, cycle);
069
070        IMarkupWriter wrappedWriter = writer.getNestedWriter();
071
072        component.renderBody(wrappedWriter, cycle);
073
074        wrappedWriter.close();
075
076        writer.end();
077
078        cycle.removeAttribute(Tapestry.LINK_COMPONENT_ATTRIBUTE_NAME);
079    }
080
081    /**
082     * Generates the onclick event handler that opens the specified url in the current window.
083     * @param url the url generated by this link
084     * @return a JavaScript onclick event handler
085     */
086    protected String getScript(String url)
087    {
088        return "window.location='" + url + "'";
089    }
090
091    /**
092     * Generates the onclick event handler that opens the specified url in the specified window or frame.
093     * @param url the url generated by this link
094     * @param target the name of the target window or frame
095     * @return a JavaScript onclick event handler
096     */
097    protected String getScript(String url, String target)
098    {
099        return "window.open('" + url + "','" + target + "')";
100    }
101}