When you internationalize your application — adapting your application for use in different languages and regions — how much you do depends on what you must later localize. Directory servers often support localized user data. OpenDJ directory server supports use of the locales provided by your Java installation, and also supports many language subtypes, for example.
Therefore if your application is not end user facing and the administrators managing your application all use the same language as you do, you might be content to use language subtypes in LDAP filters, as described in the section on Working With Search Filters.
For end user facing applications where you must return localized messages, and for applications where administrators need localized log messages, you can use the ForgeRock I18N Framework.