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Java > Open Source Codes > com > opensymphony > module > sitemesh > mapper > AgentDecoratorMapper


1 /*
2  * Title: AgentDecoratorMapper
3  * Description:
4  *
5  * This software is published under the terms of the OpenSymphony Software
6  * License version 1.1, of which a copy has been included with this
7  * distribution in the LICENSE.txt file.
8  */
9
10 package com.opensymphony.module.sitemesh.mapper;
11
12 import com.opensymphony.module.sitemesh.Config;
13 import com.opensymphony.module.sitemesh.Decorator;
14 import com.opensymphony.module.sitemesh.DecoratorMapper;
15 import com.opensymphony.module.sitemesh.Page;
16
17 import javax.servlet.http.HttpServletRequest JavaDoc;
18 import java.io.File JavaDoc;
19 import java.util.HashMap JavaDoc;
20 import java.util.Iterator JavaDoc;
21 import java.util.Map JavaDoc;
22 import java.util.Properties JavaDoc;
23
24 /**
25  * The AgentDecoratorMapper can determine the user-agent (i.e. web-browser)
26  * requesting a page, and map to a suitable Decorator.
27  *
28  * <p>This can be useful for supplying different versions of the same content
29  * for different browsers (e.g. vanilla HTML for Lynx, complex tables and frames
30  * for Netscape, extra stuff for IE5, etc).</p>
31  *
32  * <p>This can also be used to enhance search-engine ratings by using a 'bait and
33  * switch' system - this involves showing a search-engine friendly of the content
34  * to spiders only.</p>
35  *
36  * <p>When AgentDecoratorMapper is in the chain, it will request the appropriate Decorator
37  * from its parent. It will then add an extention to the filename of the Decorator, and
38  * if that file exists it shall be used as the Decorator instead. For example, if the
39  * Decorator path is <code>/blah.jsp</code> and the detected user-agent is <code>ie</code>,
40  * the path <code>/blah-ie.jsp</code> shall be used.</p>
41  *
42  * <p>The agent mappings are configured by passing properties with <code>match.</code> as a prefix.
43  * For example: 'match.MSIE'=ie , 'match.Lynx'=plain .</p>
44  *
45  * @author <a HREF="mailto:joe@truemesh.com">Joe Walnes</a>
46  * @version $Revision: 1.2 $
47  *
48  * @see com.opensymphony.module.sitemesh.DecoratorMapper
49  */
50 public final class AgentDecoratorMapper extends AbstractDecoratorMapper {
51     private Map JavaDoc map = null;
52
53     public void init(Config config, Properties JavaDoc properties, DecoratorMapper parent) throws InstantiationException JavaDoc {
54         super.init(config, properties, parent);
55         map = new HashMap JavaDoc();
56         initMap(properties);
57     }
58
59     public Decorator getDecorator(HttpServletRequest JavaDoc request, Page page) {
60         try {
61             Decorator result = null;
62             final Decorator d = super.getDecorator(request, page);
63             String JavaDoc path = modifyPath(d.getPage(), getExt(request.getHeader("User-Agent")));
64
65             File JavaDoc decFile = new File JavaDoc(config.getServletContext().getRealPath(path));
66
67             if (decFile.isFile()) {
68                 result = new DefaultDecorator(d.getName(), path, null) {
69                     public String JavaDoc getInitParameter(String JavaDoc paramName) {
70                         return d.getInitParameter(paramName);
71                     }
72                 };
73             }
74             return result == null ? super.getDecorator(request, page) : result;
75         }
76         catch (NullPointerException JavaDoc e) {
77             return super.getDecorator(request, page);
78         }
79     }
80
81     /** Get extention for user-agent. */
82     private String JavaDoc getExt(String JavaDoc userAgent) {
83         Iterator JavaDoc i = map.entrySet().iterator();
84         while (i.hasNext()) {
85             Map.Entry JavaDoc entry = (Map.Entry JavaDoc) i.next();
86             String JavaDoc curr = (String JavaDoc) entry.getKey();
87             if (userAgent.indexOf(curr) > -1) return (String JavaDoc) entry.getValue();
88         }
89         return null;
90     }
91
92     /** Change /abc/def.jsp into /abc/def-XYZ.jsp */
93     private static String JavaDoc modifyPath(String JavaDoc path, String JavaDoc ext) {
94         int dot = path.indexOf('.');
95         if (dot > -1) {
96             return path.substring(0, dot) + '-' + ext + path.substring(dot);
97         }
98         else {
99             return path + '-' + ext;
100         }
101     }
102
103     /** Initialize user-agent mappings. */
104     private void initMap(Properties JavaDoc props) {
105         Iterator JavaDoc i = props.entrySet().iterator();
106         while (i.hasNext()) {
107             Map.Entry JavaDoc entry = (Map.Entry JavaDoc) i.next();
108             String JavaDoc key = (String JavaDoc) entry.getKey();
109             if (key.startsWith("match.")) {
110                 String JavaDoc match = key.substring(6);
111                 String JavaDoc ext = (String JavaDoc) entry.getValue();
112                 map.put(match, ext);
113             }
114         }
115     }
116 }
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