001// Copyright 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.services.impl;
016
017import org.apache.tapestry.IMarkupWriter;
018import org.apache.tapestry.IPage;
019import org.apache.tapestry.IRender;
020import org.apache.tapestry.IRequestCycle;
021
022/**
023 * Contains code needed to render the <base> tag for pages. The <base> tag ensures that
024 * the base URL for the rendered page matches the location of the page template in the servlet
025 * context, so that relative URLs to static assets (images, stylesheets, etc.) will be processed
026 * correctly. This is important starting with release 4.0, where HTML templates are no longer
027 * restricted to the servlet root.
028 * <p>
029 * Note that pages outside of the application namespace (provided by the framework itself, or in a
030 * library) are "virtually located" in the application root.
031 * 
032 * @author Howard M. Lewis Ship
033 * @since 4.0
034 */
035public class BaseTagWriter implements IRender
036{
037
038    public void render(IMarkupWriter writer, IRequestCycle cycle)
039    {
040        IPage page = cycle.getPage();
041
042        StringBuffer sb = new StringBuffer();
043        sb.append("/");
044
045        if (page.getNamespace().getId() == null)
046        {
047            String name = page.getPageName();
048            int slashx = name.lastIndexOf('/');
049
050            // Include the directory and trailing slash.
051            if (slashx > 0)
052                sb.append(name.substring(0, slashx + 1));
053        }
054
055        String url = cycle.getAbsoluteURL(sb.toString());
056
057        writer.beginEmpty("base");
058        writer.attribute("href", url);
059
060        writer.println();
061    }
062
063}