1 /* 2 * Copyright (c) 2005, 2012, 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 {@link #isSupportedLocale(Locale) isSupportedLocale} 87 * methods of 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 <a href="../Locale.html#def_extensions"> 91 * locale's extensions</a> are ignored by default. (If locale's extensions should 92 * also be checked, the {@code isSupportedLocale} method must be overridden.) 93 * If neither the Java runtime environment itself nor an installed provider 94 * supports the requested locale, the methods go through a list of candidate 95 * locales and repeat the availability check for each until a match is found. 96 * The algorithm used for creating a list of candidate locales is same as 97 * the one used by <code>ResourceBunlde</code> by default (see 98 * {@link java.util.ResourceBundle.Control#getCandidateLocales getCandidateLocales} 99 * for the details). Even if a locale is resolved from the candidate list, 100 * methods that return requested objects or names are invoked with the original 101 * requested locale including {@code Locale} extensions. The Java runtime 102 * environment must support the root locale for all locale sensitive services in 103 * order to guarantee that this process terminates. 104 * <p> 105 * Providers of names (but not providers of other objects) are allowed to 106 * return null for some name requests even for locales that they claim to 107 * support by including them in their return value for 108 * <code>getAvailableLocales</code>. Similarly, the Java runtime 109 * environment itself may not have all names for all locales that it 110 * supports. This is because the sets of objects for which names are 111 * requested can be large and vary over time, so that it's not always 112 * feasible to cover them completely. If the Java runtime environment or a 113 * provider returns null instead of a name, the lookup will proceed as 114 * described above as if the locale was not supported. 115 * <p> 116 * Starting from JDK8, the search order of locale sensitive services can 117 * be configured by using the "java.locale.providers" system property. 118 * This system property declares the user's preferred order for looking up 119 * the locale sensitive services separated by a comma. It is only read at 120 * the Java runtime startup, so the later call to System.setProperty() won't 121 * affect the order. 122 * <p> 123 * For example, if the following is specified in the property: 124 * <pre> 125 * java.locale.providers=SPI,JRE 126 * </pre> 127 * where "SPI" represents the locale sensitive services implemented in the 128 * installed SPI providers, and "JRE" represents the locale sensitive services 129 * in the Java Runtime Environment, the locale sensitive services in the SPI 130 * providers are looked up first. 131 * 132 * @since 1.6 133 */ 134 public abstract class LocaleServiceProvider { 135 136 /** 137 * Sole constructor. (For invocation by subclass constructors, typically 138 * implicit.) 139 */ 140 protected LocaleServiceProvider() { 141 } 142 143 /** 144 * Returns an array of all locales for which this locale service provider 145 * can provide localized objects or names. This information is used to 146 * compose {@code getAvailableLocales()} values of the locale-dependent 147 * services, such as {@code DateFormat.getAvailableLocales()}. 148 * 149 * <p>The array returned by this method should not include two or more 150 * {@code Locale} objects only differing in their extensions. 151 * 152 * @return An array of all locales for which this locale service provider 153 * can provide localized objects or names. 154 */ 155 public abstract Locale[] getAvailableLocales(); 156 157 /** 158 * Returns {@code true} if the given {@code locale} is supported by 159 * this locale service provider. The given {@code locale} may contain 160 * <a href="../Locale.html#def_extensions">extensions<a/> that should be 161 * taken into account for the support determination. 162 * 163 * <p>The default implementation returns {@code true} if the given {@code locale} 164 * is equal to any of the available {@code Locale}s returned by 165 * {@link #getAvailableLocales()} with ignoring any extensions in both the 166 * given {@code locale} and the available locales. Concrete locale service 167 * provider implementations should override this method if those 168 * implementations are {@code Locale} extensions-aware. For example, 169 * {@code DecimalFormatSymbolsProvider} implementations will need to check 170 * extensions in the given {@code locale} to see if any numbering system is 171 * specified and can be supported. However, {@code CollatorProvider} 172 * implementations may not be affected by any particular numbering systems, 173 * and in that case, extensions for numbering systems should be ignored. 174 * 175 * @param locale a {@code Locale} to be tested 176 * @return {@code true} if the given {@code locale} is supported by this 177 * provider; {@code false} otherwise. 178 * @throws NullPointerException 179 * if the given {@code locale} is {@code null} 180 * @see Locale#hasExtensions() 181 * @see Locale#stripExtensions() 182 * @since 1.8 183 */ 184 public boolean isSupportedLocale(Locale locale) { 185 locale = locale.stripExtensions(); // throws NPE if locale == null 186 for (Locale available : getAvailableLocales()) { 187 if (locale.equals(available.stripExtensions())) { 188 return true; 189 } 190 } 191 return false; 192 } 193 }