tapestry/tapestry-framework/src/java/org/apache/tapestry/html/Relation.java

// Copyright Aug 2, 2006 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.html;

import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.tapestry.AbstractComponent;
import org.apache.tapestry.IAsset;
import org.apache.tapestry.IMarkupWriter;
import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.markup.MarkupWriterSource;
import org.apache.tapestry.util.ContentType;

import java.io.PrintWriter;
import java.io.StringWriter;

/**
 * Works with the {@link Shell} component to define and append a 
 * relationship between documents (typically a stylesheet) to 
 * the HTML response. 
 *
 * @author Andreas Andreou
 * @since 4.1.1
 */
public abstract class Relation extends AbstractComponent
{
    /**
     * {@inheritDoc}
     */
    protected void renderComponent(IMarkupWriter writer, IRequestCycle cycle)
    {
        if (!cycle.isRewinding())
        {
            Shell shell = Shell.get(cycle);

            if (shell == null)
                throw new ApplicationRuntimeException(
                        HTMLMessages.shellComponentRequired(),
                        this.getLocation(), null);

            if (getUseBody() && getHref() == null)
            {
                renderStyleTag(shell, writer, cycle);
            }
            else
            {
                renderLinkTag(shell, writer, cycle);
            }
        }
    }

    protected void renderLinkTag(Shell shell, IMarkupWriter writer, IRequestCycle cycle)
    {
        Object href = getHref();
        boolean ok = (href instanceof String) || (href instanceof IAsset);
        if (!ok)
            throw new ApplicationRuntimeException(HTMLMessages.stringOrIAssetExpected(), getLocation(), null);

        String url;
        if (href instanceof String)
        {
            url = (String) href;
        }
        else
        {
            url = ((IAsset)href).buildURL();
        }

        RelationBean bean = new RelationBean();
        bean.setHref(url);
        bean.setMedia(getMedia());
        bean.setRel(getRel());
        bean.setRev(getRev());
        bean.setTitle(getTitle());
        bean.setType(getType());
        shell.addRelation(bean);
    }

    protected void renderStyleTag(Shell shell, IMarkupWriter writer, IRequestCycle cycle)
    {
        if (getBody() == null) //nothing to include
        {
            return;
        }

        StringWriter sWriter = new StringWriter();
        IMarkupWriter nested = getMarkupWriterSource().newMarkupWriter(new PrintWriter(sWriter),
                                                                       new ContentType(writer.getContentType()));

        nested.begin("style");
        nested.attribute("type", "text/css");

        if (getMedia()!=null)
            nested.attribute("media", getMedia());
        if (getTitle()!=null)
            nested.attribute("title", getTitle());

        renderBody(nested, cycle);
        nested.close();

        shell.includeAdditionalContent(sWriter.toString());
    }

    public abstract boolean getUseBody();

    public abstract Object getHref();

    public abstract String getRel();

    public abstract String getRev();

    public abstract String getType();

    public abstract String getTitle();

    public abstract String getMedia();

    /* injected */
    public abstract MarkupWriterSource getMarkupWriterSource();

}