1 /**
2 * This file is part of the equanda project.
3 *
4 * The contents of this file are subject to the Mozilla Public License Version 1.1 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at http://www.mozilla.org/MPL/
7 *
8 * Software distributed under the License is distributed on an "AS IS" basis, WITHOUT WARRANTY OF
9 * ANY KIND, either express or implied. See the License for the specific language governing rights and
10 * limitations under the License.
11 *
12 * Alternatively, the contents of this file may be used under the terms of
13 * either the GNU General Public License Version 2 or later (the "GPL"), or
14 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
15 * in which case the provisions of the GPL or the LGPL are applicable instead
16 * of those above. If you wish to allow use of your version of this file only
17 * under the terms of either the GPL or the LGPL, and not to allow others to
18 * use your version of this file under the terms of the MPL, indicate your
19 * decision by deleting the provisions above and replace them with the notice
20 * and other provisions required by the GPL or the LGPL. If you do not delete
21 * the provisions above, a recipient may use your version of this file under
22 * the terms of any one of the MPL, the GPL or the LGPL.
23 */
24
25 package org.equanda.tapestry5.bindings;
26
27 import org.apache.tapestry5.Binding;
28
29 import java.io.IOException;
30 import java.io.InputStream;
31 import java.lang.annotation.Annotation;
32 import java.net.URL;
33 import java.util.Enumeration;
34 import java.util.Map;
35 import java.util.concurrent.ConcurrentHashMap;
36 import java.util.jar.Manifest;
37
38 /**
39 * Binding prefix which allows you to get a value from a manifest file. As multiple files may contain a value for the
40 * same key, the first encountered is used.
41 *
42 * @author <a href="mailto:joachim@progs.be">Joachim Van der Auwera</a>
43 */
44 public class ManifestBindingPrefix
45 implements Binding
46 {
47 private static final Map<String, String> CACHE = new ConcurrentHashMap<String, String>();
48 private String expression;
49
50 public ManifestBindingPrefix( String expression )
51 {
52 this.expression = expression;
53 }
54
55 public Object get()
56 {
57 try
58 {
59 // first try to get the value from the cache (these things don't really change at runtime after all)
60 String res = CACHE.get( expression );
61 if ( res != null ) return res;
62
63 ClassLoader cl = Thread.currentThread().getContextClassLoader();
64 if ( null == cl ) cl = this.getClass().getClassLoader();
65
66 Enumeration<URL> urls = cl.getResources( "META-INF/MANIFEST.MF" );
67
68 while ( null == res && urls.hasMoreElements() )
69 {
70 URL url = urls.nextElement();
71 res = get( url );
72 }
73 if ( res != null ) CACHE.put( expression, res );
74 return res;
75 }
76 catch ( Exception ex )
77 {
78 return null;
79 }
80 }
81
82 private String get( URL url )
83 throws IOException
84 {
85 InputStream in = null;
86 try
87 {
88 in = url.openStream();
89 Manifest mf = new Manifest( in );
90 return mf.getMainAttributes().getValue( expression );
91 }
92 finally
93 {
94 if ( null != in ) in.close();
95 }
96 }
97
98 @SuppressWarnings( "unchecked" )
99 public Class getBindingType()
100 {
101 return String.class;
102 }
103
104 public boolean isInvariant()
105 {
106 return false;
107 }
108
109 public void set( Object value )
110 {
111 // do nothing
112 }
113
114 public <T extends Annotation> T getAnnotation( Class<T> annotationClass )
115 {
116 return null;
117 }
118 }