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| 1 | /* | ||
| 2 | * Copyright (c) 2005, 2010, Oracle and/or its affiliates. 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. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * 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. When checking | ||
| 90 | * whether a locale is supported, the locale's extensions are ignored. | ||
| 91 | * If neither the Java runtime environment itself nor an installed provider | ||
| 92 | * supports the requested locale, the methods go through a list of candidate | ||
| 93 | * locales and repeat the availability check for each until a match is found. | ||
| 94 | * The algorithm used for creating a list of candidate locales is same as | ||
| 95 | * the one used by <code>ResourceBunlde</code> by default (see | ||
| 96 | * {@link java.util.ResourceBundle.Control#getCandidateLocales getCandidateLocales} | ||
| 97 | * for the details). Even if a locale is resolved from the candidate list, | ||
| 98 | * methods that return requested objects or names are invoked with the original | ||
| 99 | * requested locale including extensions. The Java runtime environment must | ||
| 100 | * support the root locale for all locale sensitive services in order to | ||
| 101 | * guarantee that this process terminates. | ||
| 102 | * <p> | ||
| 103 | * Providers of names (but not providers of other objects) are allowed to | ||
| 104 | * return null for some name requests even for locales that they claim to | ||
| 105 | * support by including them in their return value for | ||
| 106 | * <code>getAvailableLocales</code>. Similarly, the Java runtime | ||
| 107 | * environment itself may not have all names for all locales that it | ||
| 108 | * supports. This is because the sets of objects for which names are | ||
| 109 | * requested can be large and vary over time, so that it's not always | ||
| 110 | * feasible to cover them completely. If the Java runtime environment or a | ||
| 111 | * provider returns null instead of a name, the lookup will proceed as | ||
| 112 | * described above as if the locale was not supported. | ||
| 113 | * | ||
| 114 | * @since 1.6 | ||
| 115 | */ | ||
| 116 | public abstract class LocaleServiceProvider { | ||
| 117 | |||
| 118 | /** | ||
| 119 | * Sole constructor. (For invocation by subclass constructors, typically | ||
| 120 | * implicit.) | ||
| 121 | */ | ||
| 122 | protected LocaleServiceProvider() { | ||
| 123 | } | ||
| 124 | |||
| 125 | /** | ||
| 126 | * Returns an array of all locales for which this locale service provider | ||
| 127 | * can provide localized objects or names. | ||
| 128 | * <p> | ||
| 129 | * <b>Note:</b> Extensions in a <code>Locale</code> are ignored during | ||
| 130 | * service provider lookup. So the array returned by this method should | ||
| 131 | * not include two or more <code>Locale</code> objects only differing in | ||
| 132 | * their extensions. | ||
| 133 | * | ||
| 134 | * @return An array of all locales for which this locale service provider | ||
| 135 | * can provide localized objects or names. | ||
| 136 | */ | ||
| 137 | public abstract Locale[] getAvailableLocales(); | ||
| 138 | } | ||