i18n.apt

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                                               I18N
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                                          Fabrizio Giustina
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                                              11-11-2005
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I18N - Internationalization

   If you use displaytag in a multi-language application, you will
   probably need to translate html generated by displaytag as well.
   Displaytag supports i18n for html snippets used in the paging and
   export banner and for the title of column headers.

* i18n for displaytag resources

   Using the displaytag.properties file you can set all the messages
   handled by displaytag.

   Configuring:
   <<<paging.banner.one_item_found=One item found>>>


   Will make displaytag output One item found when only a row is
   displayed.

   In order to support other languages you can add any number of
   additional files named displaytag_LANGUAGE.properties . For example,
   you can add a displaytag_IT.properties for italian users with the
   following content:

   <<<paging.banner.one_item_found=Un solo elemento trovato>>>



   You don't need to copy all the properties in any internationalized
   file (some of them are also configuration properties which don't
   need to be translated at all). Configure displaytag properly in the
   main displaytag.properties file and then replicate only the strings
   you want to translate.

* i18n for column title

   There are a few different ways to define the content for a column
   header in the column tag:

   [[1]] specifying a title attribute: the content of the title attribute
       will be used as is for the column header

   [[2]] specifying a titlekKey attribute: the content of the titlekey
       will be used to lookup a resource in a resource bundle and the
       value will be used in the column header. If the specified key
       can't be found the ???key??? title will be displayed.

   [[3]] leaving both title and titleKey properties out, while using a
       property attribute: the content of the property attribute will
       be used to lookup a resource in the resource bundle. If not
       found, the same (capitalized) value is used for the column
       header. By default, displaytag will use JSTL to lookup the value
       in the titleKey attribute, miming the behaviour of the
       fmt:message tag. This means that you need a container which
       supports jstl and standard.jar in your classpath: if you don't
       wish to use JSTL for i18n you will have a few other options
       (read the "advanced" chapter below).

   []


* Advanced

   Displaytag will probably be used in an application where content is
   already internationalized using a specific framework, which should
   provide a way to resolve the current locale and to lookup properties
   in a resource bundle.

   Displaytag provides a way to plug-in different adapters to use the
   same i18n support you are using in your application.


* Locale resolution

   By default displaytag will use the locale specified in the request
   (i.e. the locale set in the user browser). This can be fine for a
   basic use, but you could need a way to override this selection and
   to force a different locale.

   Here comes the problem: if you already use Jstl, Struts or other
   frameworks you will know that there is no standard way to specify
   the locale to use: each framework works in a different way.

   Displaytag provides an interface LocaleResolver with a few ready to
   use implementations which match the behaviour of common frameworks.
   The locale resolver is specified in the displaytag.properties file
   using the locale.resolver key.

   If nothing is specified the locale from the request is used, as
   specified above. However, you are free to configure here any custom
   implementation of the org.displaytag.localization.LocaleResolver
   interface with a simple method resolveLocale(HttpServletRequest)

   Displaytag provides by default these ready to use implementations:
   class name behaviour
   org.displaytag.localization.I18nJstlAdapter Mimic JSTL, looking for
   a locale specified in session with the Config.FMT_LOCALE key.
   org.displaytag.localization.I18nStrutsAdapter Struts adapter, will
   look for the locale specified by Globals.LOCALE_KEY
   org.displaytag.localization.I18nWebworkAdapter Webwork2 adapter,
   will look for the locale specified by the fist LocaleProvider action
   in the stack
   org.displaytag.localization.I18nSpringAdapter Spring adapter, will
   use RequestContextUtils.getLocale() for locale resolution (which
   will in turn delegate to the Spring locale resolver)


* Resources lookup

   Other than resolving the currently used locale, your framework will
   probably provide a standard way to store i18n resources. Just like
   for the locale resolution, displaytag will allow you to plug in
   different implementations.

   Displaytag provides an interface I18nResourceProvider with a few
   ready to use implementations which match the behaviour of common
   frameworks. This is configured in displaytag.properties using the
   locale.provider key. By default the JSTL implementation is used.

   The ready to use locale resolvers are (yes, these are the same
   classes used for locale resolution, since they implement both
   interfaces):
   class name behaviour
   org.displaytag.localization.I18nJstlAdapter JSTL implementation,
   works in the same way as fmt:message. Note that this depends from
   the jakarta jstl implementation: it will also work with Resin jstl
   support, but you will still need standard.jar in the classpath.
   org.displaytag.localization.I18nStrutsAdapter Struts adapter, will
   use TagUtils.message()
   org.displaytag.localization.I18nWebworkAdapter Webwork2 adapter,
   will look for the first TextProvider action in the stack and will
   obtain a message for the given key.
   org.displaytag.localization.I18nSpringAdapter Spring adapter, will
   look for the configured messageSource and use it to obtain a value
   for the given key.