* This is the super class of all the locale sensitive service provider * interfaces (SPIs). *
* Locale sensitive service provider interfaces are interfaces that * correspond to locale sensitive classes in the {@code java.text} * and {@code java.util} packages. The interfaces enable the * construction of locale sensitive objects and the retrieval of * localized names for these packages. Locale sensitive factory methods * and methods for name retrieval in the {@code java.text} and * {@code java.util} packages use implementations of the provider * interfaces to offer support for locales beyond the set of locales * supported by the Java runtime environment itself. * *
* If a particular concrete provider class is named in more than one configuration * file, or is named in the same configuration file more than once, then the * duplicates will be ignored. The configuration file naming a particular provider * need not be in the same jar file or other distribution unit as the provider itself. * The provider must be accessible from the same class loader that was initially * queried to locate the configuration file; this is not necessarily the class loader * that loaded the file. *
* For example, an implementation of the * {@link java.text.spi.DateFormatProvider DateFormatProvider} class should * take the form of a jar file which contains the file: *
* META-INF/services/java.text.spi.DateFormatProvider ** And the file {@code java.text.spi.DateFormatProvider} should have * a line such as: *
* {@code com.foo.DateFormatProviderImpl}
*
* which is the fully qualified class name of the class implementing
* {@code DateFormatProvider}.
* * Locale sensitive factory methods and methods for name retrieval in the * {@code java.text} and {@code java.util} packages invoke * service provider methods when needed to support the requested locale. * The methods first check whether the Java runtime environment itself * supports the requested locale, and use its support if available. * Otherwise, they call the {@link #isSupportedLocale(Locale) isSupportedLocale} * methods of installed providers for the appropriate interface to find one that * supports the requested locale. If such a provider is found, its other * methods are called to obtain the requested object or name. When checking * whether a locale is supported, the {@linkplain Locale##def_extensions * locale's extensions} are ignored by default. (If locale's extensions should * also be checked, the {@code isSupportedLocale} method must be overridden.) * If neither the Java runtime environment itself nor an installed provider * supports the requested locale, the methods go through a list of candidate * locales and repeat the availability check for each until a match is found. * The algorithm used for creating a list of candidate locales is same as * the one used by {@code ResourceBundle} by default (see * {@link java.util.ResourceBundle.Control#getCandidateLocales getCandidateLocales} * for the details). Even if a locale is resolved from the candidate list, * methods that return requested objects or names are invoked with the original * requested locale including {@code Locale} extensions. The Java runtime * environment must support the root locale for all locale sensitive services in * order to guarantee that this process terminates. *
* Providers of names (but not providers of other objects) are allowed to * return null for some name requests even for locales that they claim to * support by including them in their return value for * {@code getAvailableLocales}. Similarly, the Java runtime * environment itself may not have all names for all locales that it * supports. This is because the sets of objects for which names are * requested can be large and vary over time, so that it's not always * feasible to cover them completely. If the Java runtime environment or a * provider returns null instead of a name, the lookup will proceed as * described above as if the locale was not supported. *
* The search order of locale sensitive services can * be configured by using the {@systemProperty java.locale.providers} system property. * This system property declares the user's preferred order for looking up * the locale sensitive services separated by a comma. As this property value is * read and cached only at the initialization of this class, users should specify the * property on the java launcher command line. Setting it at runtime with * {@link System#setProperty(String, String)} is discouraged and it may not affect * the order. * JDK Reference Implementation provides the following four * locale providers: *
* For example, if the following is specified in the property: *
* java.locale.providers=SPI,CLDR,COMPAT ** the locale sensitive services in the SPI providers are looked up first. If the * desired locale sensitive service is not available, then the runtime looks for CLDR, * COMPAT in that order. *
* The default order for looking up the preferred locale providers is "CLDR,COMPAT", * so specifying "CLDR,COMPAT" is identical to the default behavior. Applications which * require implementations of the locale sensitive services must explicitly specify * "SPI" in order for the Java runtime to load them from the classpath. * * @since 1.6 */ public abstract class LocaleServiceProvider { private static Void checkPermission() { @SuppressWarnings("removal") SecurityManager sm = System.getSecurityManager(); if (sm != null) { sm.checkPermission(new RuntimePermission("localeServiceProvider")); } return null; } private LocaleServiceProvider(Void ignore) { } /** * Initializes a new locale service provider. * * @throws SecurityException * If a security manager has been installed and it denies * {@link RuntimePermission RuntimePermission("localeServiceProvider")} */ protected LocaleServiceProvider() { this(checkPermission()); } /** * {@return an array of all locales for which this locale service provider * can provide localized objects or names} * * This information is used to compose {@code getAvailableLocales()} * values of the locale-dependent services, such as * {@code DateFormat.getAvailableLocales()}. * *
The array returned by this method should not include two or more * {@code Locale} objects only differing in their extensions. */ public abstract Locale[] getAvailableLocales(); /** * Returns {@code true} if the given {@code locale} is supported by * this locale service provider. The given {@code locale} may contain * {@linkplain Locale##def_extensions extensions} that should be * taken into account for the support determination. * *
The default implementation returns {@code true} if the given {@code locale} * is equal to any of the available {@code Locale}s returned by * {@link #getAvailableLocales()} with ignoring any extensions in both the * given {@code locale} and the available locales. Concrete locale service * provider implementations should override this method if those * implementations are {@code Locale} extensions-aware. For example, * {@code DecimalFormatSymbolsProvider} implementations will need to check * extensions in the given {@code locale} to see if any numbering system is * specified and can be supported. However, {@code CollatorProvider} * implementations may not be affected by any particular numbering systems, * and in that case, extensions for numbering systems should be ignored. * * @param locale a {@code Locale} to be tested * @return {@code true} if the given {@code locale} is supported by this * provider; {@code false} otherwise. * @throws NullPointerException * if the given {@code locale} is {@code null} * @see Locale#hasExtensions() * @see Locale#stripExtensions() * @since 1.8 */ public boolean isSupportedLocale(Locale locale) { locale = locale.stripExtensions(); // throws NPE if locale == null for (Locale available : getAvailableLocales()) { if (locale.equals(available.stripExtensions())) { return true; } } return false; } }