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.text
and 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.text and
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.
Packaging of Locale Sensitive Service Provider Implementations
Implementations of these locale sensitive services are packaged using the
Java Extension Mechanism
as installed extensions. A provider identifies itself with a
provider-configuration file in the resource directory META-INF/services,
using the fully qualified provider interface class name as the file name.
The file should contain a list of fully-qualified concrete provider class names,
one per line. A line is terminated by any one of a line feed ('\n'), a carriage
return ('\r'), or a carriage return followed immediately by a line feed. Space
and tab characters surrounding each name, as well as blank lines, are ignored.
The comment character is '#' ('\u0023'); on each line all characters following
the first comment character are ignored. The file must be encoded in UTF-8.
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 java.text.spi.DateFormatProvider should have
a line such as:
com.foo.DateFormatProviderImpl
which is the fully qualified class name of the class implementing
DateFormatProvider.
Invocation of Locale Sensitive Services
Locale sensitive factory methods and methods for name retrieval in the
java.text and 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 getAvailableLocales() 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. If neither
the Java runtime environment itself nor an installed provider supports
the requested locale, a fallback locale is constructed by replacing the
first of the variant, country, or language strings of the locale that's
not an empty string with an empty string, and the lookup process is
restarted. In the case that the variant contains one or more '_'s, the
fallback locale is constructed by replacing the variant with a new variant
which eliminates the last '_' and the part following it. Even if a
fallback occurs, methods that return requested objects or name are
invoked with the original locale before the fallback.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. | 