1 package org.codehaus.plexus.i18n;
2
3 /*
4 * Copyright 2001-2007 Codehaus Foundation.
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * 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, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18
19 import java.util.ArrayList;
20 import java.util.Collections;
21 import java.util.Iterator;
22 import java.util.Locale;
23 import java.util.NoSuchElementException;
24 import java.util.StringTokenizer;
25
26 /**
27 * Parses the HTTP <code>Accept-Language</code> header as per section
28 * 14.4 of RFC 2068 (HTTP 1.1 header field definitions).
29 *
30 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
31 * @version $Id: I18NTokenizer.java 6675 2007-07-20 23:05:53Z olamy $
32 *
33 * @todo Move this class out of here as its purely web related.
34 */
35 public class I18NTokenizer
36 implements Iterator
37 {
38 /**
39 * Separates elements of the <code>Accept-Language</code> HTTP
40 * header.
41 */
42 private static final String LOCALE_SEPARATOR = ",";
43
44 /**
45 * Separates locale from quality within elements.
46 */
47 private static final char QUALITY_SEPARATOR = ';';
48
49 /**
50 * The default quality value for an <code>AcceptLanguage</code>
51 * object.
52 */
53 private static final Float DEFAULT_QUALITY = new Float(1.0f);
54
55 /**
56 * The parsed locales.
57 */
58 private ArrayList locales = new ArrayList(3);
59
60 /**
61 * Parses the <code>Accept-Language</code> header.
62 *
63 * @param header The <code>Accept-Language</code> header
64 * (i.e. <code>en, es;q=0.8, zh-TW;q=0.1</code>).
65 */
66 public I18NTokenizer(String header)
67 {
68 StringTokenizer tok = new StringTokenizer(header, LOCALE_SEPARATOR);
69 while (tok.hasMoreTokens())
70 {
71 AcceptLanguage acceptLang = new AcceptLanguage();
72 String element = tok.nextToken().trim();
73 int index;
74
75 // Record and cut off any quality value that comes after a
76 // semi-colon.
77 if ( (index = element.indexOf(QUALITY_SEPARATOR)) != -1 )
78 {
79 String q = element.substring(index);
80 element = element.substring(0, index);
81 if ( (index = q.indexOf('=')) != -1 )
82 {
83 try
84 {
85 acceptLang.quality =
86 Float.valueOf(q.substring(index + 1));
87 }
88 catch (NumberFormatException useDefault)
89 {
90 }
91 }
92 }
93
94 element = element.trim();
95
96 // Create a Locale from the language. A dash may separate the
97 // language from the country.
98 if ( (index = element.indexOf('-')) == -1 )
99 {
100 // No dash means no country.
101 acceptLang.locale = new Locale(element, "");
102 }
103 else
104 {
105 acceptLang.locale = new Locale(element.substring(0, index),
106 element.substring(index + 1));
107 }
108
109 locales.add(acceptLang);
110 }
111
112 // Sort by quality in descending order.
113 Collections.sort(locales, Collections.reverseOrder());
114 }
115
116 /**
117 * @return Whether there are more locales.
118 */
119 public boolean hasNext()
120 {
121 return !locales.isEmpty();
122 }
123
124 /**
125 * Creates a <code>Locale</code> from the next element of the
126 * <code>Accept-Language</code> header.
127 *
128 * @return The next highest-rated <code>Locale</code>.
129 * @throws NoSuchElementException No more locales.
130 */
131 public Object next()
132 {
133 if (locales.isEmpty())
134 {
135 throw new NoSuchElementException();
136 }
137 return ((AcceptLanguage) locales.remove(0)).locale;
138 }
139
140 /**
141 * Not implemented.
142 */
143 public final void remove()
144 {
145 throw new UnsupportedOperationException(getClass().getName() +
146 " does not support remove()");
147 }
148
149 /**
150 * Struct representing an element of the HTTP
151 * <code>Accept-Language</code> header.
152 */
153 private class AcceptLanguage implements Comparable
154 {
155 /**
156 * The language and country.
157 */
158 Locale locale;
159
160 /**
161 * The quality of our locale (as values approach
162 * <code>1.0</code>, they indicate increased user preference).
163 */
164 Float quality = DEFAULT_QUALITY;
165
166 public final int compareTo(Object acceptLang)
167 {
168 return quality.compareTo( ((AcceptLanguage) acceptLang).quality );
169 }
170 }
171 }