1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19
20 package org.apache.myfaces.component.html.util;
21
22 import java.io.IOException;
23 import java.io.PrintWriter;
24
25 import javax.servlet.ServletContext;
26 import javax.servlet.http.HttpServletRequest;
27 import javax.servlet.http.HttpServletResponse;
28
29 import org.apache.commons.logging.Log;
30 import org.apache.commons.logging.LogFactory;
31 import org.apache.myfaces.renderkit.html.util.ResourceLoader;
32
33 /**
34 * Serve component-specific resources that MUST be embedded in the HEAD
35 * of an html page.
36 * <p>
37 * Currently, there is only one case where resources <i>must</i> be in the
38 * document head: inline CSS or links to CSS stylesheets.
39 * <p>
40 * When using the StreamingAddResource class, a single link is output in the
41 * document HEAD for each page which embeds the name of this class in the url.
42 * This causes the browser to make a GET request to that link url when rendering
43 * the page; the tomahawk extensions filter sees the embedded ResourceLoader
44 * class name and creates an instance of this class to handle the request.
45 * <p>
46 * Note that for other resources the StreamingAddResources class generates urls
47 * that embed the standard MyFacesResourceLoader url, ie this class does not
48 * handle serving of resources other than the ones that MUST be in the head
49 * section.
50 * <p>
51 * The url also embeds a "request id" which is unique for each page served. This
52 * id is then used as a key into a global-scoped cache. The data there was inserted
53 * during the previous request, and is deleted as soon as it is served up by this
54 * class.
55 */
56 public class StreamingResourceLoader implements ResourceLoader
57 {
58 private final static Log log = LogFactory.getLog(StreamingResourceLoader.class);
59
60 public StreamingResourceLoader()
61 {
62 }
63
64 public void serveResource(ServletContext context, HttpServletRequest request, HttpServletResponse response, String resourceUri) throws IOException
65 {
66 // Technically here we should check for "/header.css" on the end of the url. But right now,
67 // this ResourceLoader only ever serves that one "virtual" css resource, so this request
68 // cannot be for anything else...
69
70 int pos = resourceUri.indexOf("/");
71 Long requestId = new Long(Long.parseLong(resourceUri.substring(0, pos), 10));
72
73 StreamingThreadManager manager = (StreamingThreadManager) context.getAttribute(StreamingThreadManager.KEY);
74
75 StreamingThreadManager.HeaderInfoEntry headerInfoEntry = manager.getHeaderInfo(requestId);
76 if (headerInfoEntry == null)
77 {
78 log.warn("No streamable resources found for request: " + requestId + " resourceUri: " + resourceUri);
79 return;
80 }
81
82 /*
83 * Ensure the browser doesn't cache this response. We never generate the same url twice
84 * (the requestId value embedded in the url changes for each request) so storing the
85 * response in a browser cache is just a waste; the cached data would never be used again.
86 */
87 response.setHeader("pragma", "no-cache");
88 response.setHeader("Cache-control", "no-cache, must-revalidate");
89
90 try
91 {
92 PrintWriter pw = response.getWriter();
93
94 StreamingAddResource.StreamablePositionedInfo positionedInfo;
95 try
96 {
97 while ((positionedInfo = headerInfoEntry.fetchInfo()) != null)
98 {
99 positionedInfo.writePositionedInfo(response, pw);
100 pw.flush();
101 }
102 pw.close();
103 }
104 catch (InterruptedException e)
105 {
106 throw (IOException) new IOException().initCause(e);
107 }
108 }
109 finally
110 {
111 manager.removeHeaderInfo(requestId);
112 }
113 }
114
115 }