1 /* 2 * Copyright (c) 2005, 2015, 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 * 45 * <h3>Packaging of Locale Sensitive Service Provider Implementations</h3> 46 * Implementations of these locale sensitive services can be made available 47 * by adding them to the application's class path. A provider identifies itself with a 48 * provider-configuration file in the resource directory META-INF/services, 49 * using the fully qualified provider interface class name as the file name. 50 * The file should contain a list of fully-qualified concrete provider class names, 51 * one per line. A line is terminated by any one of a line feed ('\n'), a carriage 52 * return ('\r'), or a carriage return followed immediately by a line feed. Space 53 * and tab characters surrounding each name, as well as blank lines, are ignored. 54 * The comment character is '#' ('\u0023'); on each line all characters following 55 * the first comment character are ignored. The file must be encoded in UTF-8. 56 * <p> 57 * If a particular concrete provider class is named in more than one configuration 58 * file, or is named in the same configuration file more than once, then the 59 * duplicates will be ignored. The configuration file naming a particular provider 60 * need not be in the same jar file or other distribution unit as the provider itself. 61 * The provider must be accessible from the same class loader that was initially 62 * queried to locate the configuration file; this is not necessarily the class loader 63 * that loaded the file. 64 * <p> 65 * For example, an implementation of the 66 * {@link java.text.spi.DateFormatProvider DateFormatProvider} class should 67 * take the form of a jar file which contains the file: 68 * <pre> 69 * META-INF/services/java.text.spi.DateFormatProvider 70 * </pre> 71 * And the file <code>java.text.spi.DateFormatProvider</code> should have 72 * a line such as: 73 * <pre> 74 * <code>com.foo.DateFormatProviderImpl</code> 75 * </pre> 76 * which is the fully qualified class name of the class implementing 77 * <code>DateFormatProvider</code>. 78 * <h4>Invocation of Locale Sensitive Services</h4> 79 * <p> 80 * Locale sensitive factory methods and methods for name retrieval in the 81 * <code>java.text</code> and <code>java.util</code> packages invoke 82 * service provider methods when needed to support the requested locale. 83 * The methods first check whether the Java runtime environment itself 84 * supports the requested locale, and use its support if available. 85 * Otherwise, they call the {@link #isSupportedLocale(Locale) isSupportedLocale} 86 * methods of installed providers for the appropriate interface to find one that 87 * supports the requested locale. If such a provider is found, its other 88 * methods are called to obtain the requested object or name. When checking 89 * whether a locale is supported, the <a href="../Locale.html#def_extensions"> 90 * locale's extensions</a> are ignored by default. (If locale's extensions should 91 * also be checked, the {@code isSupportedLocale} method must be overridden.) 92 * If neither the Java runtime environment itself nor an installed provider 93 * supports the requested locale, the methods go through a list of candidate 94 * locales and repeat the availability check for each until a match is found. 95 * The algorithm used for creating a list of candidate locales is same as 96 * the one used by <code>ResourceBundle</code> by default (see 97 * {@link java.util.ResourceBundle.Control#getCandidateLocales getCandidateLocales} 98 * for the details). Even if a locale is resolved from the candidate list, 99 * methods that return requested objects or names are invoked with the original 100 * requested locale including {@code Locale} extensions. The Java runtime 101 * environment must support the root locale for all locale sensitive services in 102 * order to guarantee that this process terminates. 103 * <p> 104 * Providers of names (but not providers of other objects) are allowed to 105 * return null for some name requests even for locales that they claim to 106 * support by including them in their return value for 107 * <code>getAvailableLocales</code>. Similarly, the Java runtime 108 * environment itself may not have all names for all locales that it 109 * supports. This is because the sets of objects for which names are 110 * requested can be large and vary over time, so that it's not always 111 * feasible to cover them completely. If the Java runtime environment or a 112 * provider returns null instead of a name, the lookup will proceed as 113 * described above as if the locale was not supported. 114 * <p> 115 * The search order of locale sensitive services can 116 * be configured by using the "java.locale.providers" system property. 117 * This system property declares the user's preferred order for looking up 118 * the locale sensitive services separated by a comma. It is only read at 119 * the Java runtime startup, so the later call to System.setProperty() won't 120 * affect the order. 121 * <p> 122 * Java Runtime Environment provides the following four locale providers: 123 * <ul> 124 * <li> "CLDR": A provider based on Unicode Consortium's 125 * <a href="http://cldr.unicode.org/">CLDR Project</a>. 126 * <li> "JRE": represents the locale sensitive services that is compatible 127 * with the prior JDK releases (same with JDK8's "JRE"). 128 * <li> "SPI": represents the locale sensitive services implementing the subclasses of 129 * this {@code LocaleServiceProvider} class. 130 * <li> "HOST": A provider that reflects the user's custom settings in the 131 * underlying operating system. This provider may not be available, depending 132 * on the Java Runtime Environment implementation. 133 * </ul> 134 * <p> 135 * For example, if the following is specified in the property: 136 * <pre> 137 * java.locale.providers=SPI,CLDR,JRE 138 * </pre> 139 * the locale sensitive services in the SPI providers are looked up first. If the 140 * desired locale sensitive service is not available, then the runtime looks for CLDR, 141 * JRE in that order. 142 * <p> 143 * The default order for looking up the preferred locale providers is "CLDR,JRE,SPI", 144 * so specifying "CLDR,JRE,SPI" is identical to the default behavior. 145 * 146 * @since 1.6 147 */ 148 public abstract class LocaleServiceProvider { 149 150 private static Void checkPermission() { 151 SecurityManager sm = System.getSecurityManager(); 152 if (sm != null) { 153 sm.checkPermission(new RuntimePermission("localeServiceProvider")); 154 } 155 return null; 156 } 157 private LocaleServiceProvider(Void ignore) { } 158 159 /** 160 * Initializes a new locale service provider. 161 * 162 * @throws SecurityException 163 * If a security manager has been installed and it denies 164 * {@link RuntimePermission RuntimePermission("localeServiceProvider")} 165 */ 166 protected LocaleServiceProvider() { 167 this(checkPermission()); 168 } 169 170 /** 171 * Returns an array of all locales for which this locale service provider 172 * can provide localized objects or names. This information is used to 173 * compose {@code getAvailableLocales()} values of the locale-dependent 174 * services, such as {@code DateFormat.getAvailableLocales()}. 175 * 176 * <p>The array returned by this method should not include two or more 177 * {@code Locale} objects only differing in their extensions. 178 * 179 * @return An array of all locales for which this locale service provider 180 * can provide localized objects or names. 181 */ 182 public abstract Locale[] getAvailableLocales(); 183 184 /** 185 * Returns {@code true} if the given {@code locale} is supported by 186 * this locale service provider. The given {@code locale} may contain 187 * <a href="../Locale.html#def_extensions">extensions</a> that should be 188 * taken into account for the support determination. 189 * 190 * <p>The default implementation returns {@code true} if the given {@code locale} 191 * is equal to any of the available {@code Locale}s returned by 192 * {@link #getAvailableLocales()} with ignoring any extensions in both the 193 * given {@code locale} and the available locales. Concrete locale service 194 * provider implementations should override this method if those 195 * implementations are {@code Locale} extensions-aware. For example, 196 * {@code DecimalFormatSymbolsProvider} implementations will need to check 197 * extensions in the given {@code locale} to see if any numbering system is 198 * specified and can be supported. However, {@code CollatorProvider} 199 * implementations may not be affected by any particular numbering systems, 200 * and in that case, extensions for numbering systems should be ignored. 201 * 202 * @param locale a {@code Locale} to be tested 203 * @return {@code true} if the given {@code locale} is supported by this 204 * provider; {@code false} otherwise. 205 * @throws NullPointerException 206 * if the given {@code locale} is {@code null} 207 * @see Locale#hasExtensions() 208 * @see Locale#stripExtensions() 209 * @since 1.8 210 */ 211 public boolean isSupportedLocale(Locale locale) { 212 locale = locale.stripExtensions(); // throws NPE if locale == null 213 for (Locale available : getAvailableLocales()) { 214 if (locale.equals(available.stripExtensions())) { 215 return true; 216 } 217 } 218 return false; 219 } 220 }