tapestry/tapestry-framework/src/java/org/apache/tapestry/services/impl/BaseTagWriter.java

// Copyright 2005 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.services.impl;

import org.apache.tapestry.IMarkupWriter;
import org.apache.tapestry.IPage;
import org.apache.tapestry.IRender;
import org.apache.tapestry.IRequestCycle;

/**
 * Contains code needed to render the <base> tag for pages. The <base> tag ensures that
 * the base URL for the rendered page matches the location of the page template in the servlet
 * context, so that relative URLs to static assets (images, stylesheets, etc.) will be processed
 * correctly. This is important starting with release 4.0, where HTML templates are no longer
 * restricted to the servlet root.
 * <p>
 * Note that pages outside of the application namespace (provided by the framework itself, or in a
 * library) are "virtually located" in the application root.
 * 
 * @author Howard M. Lewis Ship
 * @since 4.0
 */
public class BaseTagWriter implements IRender
{

    public void render(IMarkupWriter writer, IRequestCycle cycle)
    {
        IPage page = cycle.getPage();

        StringBuffer sb = new StringBuffer();
        sb.append("/");

        if (page.getNamespace().getId() == null)
        {
            String name = page.getPageName();
            int slashx = name.lastIndexOf('/');

            // Include the directory and trailing slash.
            if (slashx > 0)
                sb.append(name.substring(0, slashx + 1));
        }

        String url = cycle.getAbsoluteURL(sb.toString());

        writer.beginEmpty("base");
        writer.attribute("href", url);
        writer.printRaw("<!--[if IE]></base><![endif]-->");

        writer.println();
    }

}