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JSF components and utilities that can be used with any JSF implementation. This library is based on the JSF1.1 version of Tomahawk, but with minor source code and build changes to take advantage of JSF2.1 features. A JSF2.1 implementation is required to use this version of the Tomahawk library.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.myfaces.component.html.util;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.myfaces.renderkit.html.util.ResourceLoader;

/**
 * Serve component-specific resources that MUST be embedded in the HEAD
 * of an html page.
 * 
 * Currently, there is only one case where resources must be in the
 * document head: inline CSS or links to CSS stylesheets.
 * 

 * When using the StreamingAddResource class, a single link is output in the
 * document HEAD for each page which embeds the name of this class in the url.
 * This causes the browser to make a GET request to that link url when rendering
 * the page; the tomahawk extensions filter sees the embedded ResourceLoader
 * class name and creates an instance of this class to handle the request.
 * 

 * Note that for other resources the StreamingAddResources class generates urls
 * that embed the standard MyFacesResourceLoader url, ie this class does not
 * handle serving of resources other than the ones that MUST be in the head 
 * section.
 * 
 * The url also embeds a "request id" which is unique for each page served. This
 * id is then used as a key into a global-scoped cache. The data there was inserted
 * during the previous request, and is deleted as soon as it is served up by this 
 * class.
 */
public class StreamingResourceLoader implements ResourceLoader
{
    private final static Log log = LogFactory.getLog(StreamingResourceLoader.class);
    
    public StreamingResourceLoader()
    {
    }

    public void serveResource(ServletContext context, HttpServletRequest request, HttpServletResponse response, String resourceUri) throws IOException
    {
        // Technically here we should check for "/header.css" on the end of the url. But right now,
        // this ResourceLoader only ever serves that one "virtual" css resource, so this request
        // cannot be for anything else...

        int pos = resourceUri.indexOf("/");
        Long requestId = new Long(Long.parseLong(resourceUri.substring(0, pos), 10));
        
        StreamingThreadManager manager = (StreamingThreadManager) context.getAttribute(StreamingThreadManager.KEY);
        
        StreamingThreadManager.HeaderInfoEntry headerInfoEntry = manager.getHeaderInfo(requestId);
        if (headerInfoEntry == null)
        {
            log.warn("No streamable resources found for request: " + requestId + " resourceUri: " + resourceUri);
            return;
        }

        /*
         * Ensure the browser doesn't cache this response. We never generate the same url twice
         * (the requestId value embedded in the url changes for each request) so storing the
         * response in a browser cache is just a waste; the cached data would never be used again.
         */
        response.setHeader("pragma", "no-cache");
        response.setHeader("Cache-control", "no-cache, must-revalidate");
        
        try
        {
            PrintWriter pw = response.getWriter();
            
            StreamingAddResource.StreamablePositionedInfo positionedInfo;
            try
            {
                while ((positionedInfo = headerInfoEntry.fetchInfo()) != null)
                {
                    positionedInfo.writePositionedInfo(response, pw);
                    pw.flush();
                }
                pw.close();
            }
            catch (InterruptedException e)
            {
                throw (IOException) new IOException().initCause(e);
            }
        }
        finally
        {
            manager.removeHeaderInfo(requestId);
        }
    }

}