public abstract class LocaleServiceProvider extends Object
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
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
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
DateFormatProvider class should
take the form of a jar file which contains the file:
META-INF/services/java.text.spi.DateFormatProviderAnd the file
java.text.spi.DateFormatProvidershould have a line such as:
which is the fully qualified class name of the class implementing
Locale sensitive factory methods and methods for name retrieval in the
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
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
locale's extensions are ignored by default. (If locale's extensions should
also be checked, the
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
ResourceBundle by default (see
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
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
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.
Starting from JDK8, the search order of locale sensitive services can be configured by using the "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. It is only read at the Java runtime startup, so the later call to System.setProperty() won't affect the order.
For example, if the following is specified in the property:
java.locale.providers=SPI,JREwhere "SPI" represents the locale sensitive services implemented in the installed SPI providers, and "JRE" represents the locale sensitive services in the Java Runtime Environment, the locale sensitive services in the SPI providers are looked up first.
There are two other possible locale sensitive service providers, i.e., "CLDR" which is a provider based on Unicode Consortium's CLDR Project, and "HOST" which is a provider that reflects the user's custom settings in the underlying operating system. These two providers may not be available, depending on the Java Runtime Environment implementation. Specifying "JRE,SPI" is identical to the default behavior, which is compatibile with the prior releases.
|Modifier||Constructor and Description|
|Modifier and Type||Method and Description|
Returns an array of all locales for which this locale service provider can provide localized objects or names.
public abstract Locale getAvailableLocales()
getAvailableLocales()values of the locale-dependent services, such as
The array returned by this method should not include two or more
Locale objects only differing in their extensions.
public boolean isSupportedLocale(Locale locale)
trueif the given
localeis supported by this locale service provider. The given
localemay contain extensions that should be taken into account for the support determination.
The default implementation returns
true if the given
is equal to any of the available
Locales returned by
getAvailableLocales() with ignoring any extensions in both the
locale and the available locales. Concrete locale service
provider implementations should override this method if those
Locale extensions-aware. For example,
DecimalFormatSymbolsProvider implementations will need to check
extensions in the given
locale to see if any numbering system is
specified and can be supported. However,
implementations may not be affected by any particular numbering systems,
and in that case, extensions for numbering systems should be ignored.