1 /*
2 * Copyright 2005-2006 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.util.spi;
27
28 import java.util.Locale;
29
30 /**
31 * <p>
32 * This is the super class of all the locale sensitive service provider
33 * interfaces (SPIs).
34 * <p>
35 * Locale sensitive service provider interfaces are interfaces that
36 * correspond to locale sensitive classes in the <code>java.text</code>
37 * and <code>java.util</code> packages. The interfaces enable the
38 * construction of locale sensitive objects and the retrieval of
39 * localized names for these packages. Locale sensitive factory methods
40 * and methods for name retrieval in the <code>java.text</code> and
41 * <code>java.util</code> packages use implementations of the provider
42 * interfaces to offer support for locales beyond the set of locales
43 * supported by the Java runtime environment itself.
44 * <p>
45 * <h4>Packaging of Locale Sensitive Service Provider Implementations</h4>
46 * Implementations of these locale sensitive services are packaged using the
47 * <a href="../../../../technotes/guides/extensions/index.html">Java Extension Mechanism</a>
48 * as installed extensions. A provider identifies itself with a
49 * provider-configuration file in the resource directory META-INF/services,
50 * using the fully qualified provider interface class name as the file name.
51 * The file should contain a list of fully-qualified concrete provider class names,
52 * one per line. A line is terminated by any one of a line feed ('\n'), a carriage
53 * return ('\r'), or a carriage return followed immediately by a line feed. Space
54 * and tab characters surrounding each name, as well as blank lines, are ignored.
55 * The comment character is '#' ('\u0023'); on each line all characters following
56 * the first comment character are ignored. The file must be encoded in UTF-8.
57 * <p>
58 * If a particular concrete provider class is named in more than one configuration
59 * file, or is named in the same configuration file more than once, then the
60 * duplicates will be ignored. The configuration file naming a particular provider
61 * need not be in the same jar file or other distribution unit as the provider itself.
62 * The provider must be accessible from the same class loader that was initially
63 * queried to locate the configuration file; this is not necessarily the class loader
64 * that loaded the file.
65 * <p>
66 * For example, an implementation of the
67 * {@link java.text.spi.DateFormatProvider DateFormatProvider} class should
68 * take the form of a jar file which contains the file:
69 * <pre>
70 * META-INF/services/java.text.spi.DateFormatProvider
71 * </pre>
72 * And the file <code>java.text.spi.DateFormatProvider</code> should have
73 * a line such as:
74 * <pre>
75 * <code>com.foo.DateFormatProviderImpl</code>
76 * </pre>
77 * which is the fully qualified class name of the class implementing
78 * <code>DateFormatProvider</code>.
79 * <h4>Invocation of Locale Sensitive Services</h4>
80 * <p>
81 * Locale sensitive factory methods and methods for name retrieval in the
82 * <code>java.text</code> and <code>java.util</code> packages invoke
83 * service provider methods when needed to support the requested locale.
84 * The methods first check whether the Java runtime environment itself
85 * supports the requested locale, and use its support if available.
86 * Otherwise, they call the <code>getAvailableLocales()</code> methods of
87 * installed providers for the appropriate interface to find one that
88 * supports the requested locale. If such a provider is found, its other
89 * methods are called to obtain the requested object or name. If neither
90 * the Java runtime environment itself nor an installed provider supports
91 * the requested locale, a fallback locale is constructed by replacing the
92 * first of the variant, country, or language strings of the locale that's
93 * not an empty string with an empty string, and the lookup process is
94 * restarted. In the case that the variant contains one or more '_'s, the
95 * fallback locale is constructed by replacing the variant with a new variant
96 * which eliminates the last '_' and the part following it. Even if a
97 * fallback occurs, methods that return requested objects or name are
98 * invoked with the original locale before the fallback.The Java runtime
99 * environment must support the root locale for all locale sensitive services
100 * in order to guarantee that this process terminates.
101 * <p>
102 * Providers of names (but not providers of other objects) are allowed to
103 * return null for some name requests even for locales that they claim to
104 * support by including them in their return value for
105 * <code>getAvailableLocales</code>. Similarly, the Java runtime
106 * environment itself may not have all names for all locales that it
107 * supports. This is because the sets of objects for which names are
108 * requested can be large and vary over time, so that it's not always
109 * feasible to cover them completely. If the Java runtime environment or a
110 * provider returns null instead of a name, the lookup will proceed as
111 * described above as if the locale was not supported.
112 *
113 * @since 1.6
114 */
115 public abstract class LocaleServiceProvider {
116
117 /**
118 * Sole constructor. (For invocation by subclass constructors, typically
119 * implicit.)
120 */
121 protected LocaleServiceProvider() {
122 }
123
124 /**
125 * Returns an array of all locales for which this locale service provider
126 * can provide localized objects or names.
127 *
128 * @return An array of all locales for which this locale service provider
129 * can provide localized objects or names.
130 */
131 public abstract Locale[] getAvailableLocales();
132 }
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