usn.i18n.nobundle

Class I18nHandler

java.lang.Object

usn.i18n.nobundle.I18nHandler

Direct Known Subclasses:

I18nHandlerForSingleUser, I18nHandlerInContext

public class I18nHandler
extends Object

The basic handler class in the hierarchy that implements an approach when user preferences are either retrieved from the application or stored locally in single-user-per-application-instance cases; to be subclassed by an application.

Version:

2013-06-17

This class specifies the most basic handler methods. It also declares and sustains an I18nHandler singleton to be used by I18nItem subclasses.

An application would normally subclass this class and:

• override the getUserLocaleTags() method;
• optionally override the getDefaultLocaleTag() method;

See package info for a usage example.

Author:

Sergey Ushakov, s-n-ushakov@yandex.ru

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	I18nHandler() The no-argument constructor to be used by subclasses.

Method Summary

Methods

Modifier and Type	Method and Description
protected String	findBestLocaleTag(I18nItem item) A utility method to be used by I18nItem subclasses to find the best locale suitable for given user for given I18nItem instance.
protected String	findBestLocaleTag(I18nItem item, String[] userLocaleTags) The core method to be used by I18nHandler subclasses to find the best locale suitable for given user for given I18nItem instance, with user locale preferences already having been identified.
protected String	getDefaultLocaleTag() The method to be used internally to obtain the application-wide default locale; to be overridden, should the application-wide default locale be different from the system locale.
protected String[]	getUserLocaleTags() The method to be used internally to obtain an array of user's preferred locales, identified via their language tags, best preferred coming first; to be overridden to implement an application-specific approach to user locale preferences.
static Locale	localeForLanguageTag(String localeTag) The procedure to query and populate the local locale cache, indexed by language tags; made public to allow I18nItem subclassing.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

I18nHandler

protected I18nHandler()

The no-argument constructor to be used by subclasses. Checks and assigns the I18nHandler singleton.

Method Detail

localeForLanguageTag

public static Locale localeForLanguageTag(String localeTag)

The procedure to query and populate the local locale cache, indexed by language tags; made public to allow I18nItem subclassing.

Parameters:

localeTag - the locale language tag to query for

Returns:

a Locale instance, either from cache or new

findBestLocaleTag

protected String findBestLocaleTag(I18nItem item,
                       String[] userLocaleTags)
                            throws NoSuchElementException

The core method to be used by I18nHandler subclasses to find the best locale suitable for given user for given I18nItem instance, with user locale preferences already having been identified. Tries to find a match for user preferences first, either exact match for user preferred locale or approximate match for language part thereof, then for application default locale, then for any English flavor, and finally tries to return just anything available. In case of several locales available for one language in the I18nItem instance, and only language being matched, the last locale supplied upon item construction wins.

Parameters:

item - an internationalized message instance

userLocaleTags - an array of user preferred locales represented by their language tags, best preferred coming first

Returns:

language tag for the best suitable locale found

Throws:

NoSuchElementException - should the item happen to be empty

findBestLocaleTag

protected String findBestLocaleTag(I18nItem item)
                            throws NoSuchElementException

A utility method to be used by I18nItem subclasses to find the best locale suitable for given user for given I18nItem instance.

Parameters:

item - an I18nItem instance to be served

Returns:

language tag for the best suitable locale found

Throws:

NoSuchElementException - should the item happen to be empty

getDefaultLocaleTag

protected String getDefaultLocaleTag()

The method to be used internally to obtain the application-wide default locale; to be overridden, should the application-wide default locale be different from the system locale.

Returns:

the locale language tag for default locale of an application

getUserLocaleTags

protected String[] getUserLocaleTags()

The method to be used internally to obtain an array of user's preferred locales, identified via their language tags, best preferred coming first; to be overridden to implement an application-specific approach to user locale preferences. A subclass may retrieve user locale preferences either by querying the application or simply storing user preferences locally like I18nHandlerForSingleUser.

Returns:

an array of locale language tags for user's preferred locales, best preferred coming first