Parse Accept-Language header in Java

Question

The accept-language header in request is usually a long complex string -

Eg.

Accept-Language : en-ca,en;q=0.8,en-us;q=0.6,de-de;q=0.4,de;q=0.2
         


        

Answer 1

ServletRequest.getLocale() is certainly the best option if it is available and not overwritten as some frameworks do.

For all other cases Java 8 offers Locale.LanguageRange.parse() as previously mentioned by Quiang Li. This however only gives back a Language String, not a Locale. To parse the language strings you can use Locale.forLanguageTag() (available since Java 7):

    final List acceptedLocales = new ArrayList<>();
    final String userLocale = request.getHeader("Accept-Language");
    if (userLocale != null) {
        final List ranges = Locale.LanguageRange.parse(userLocale);

        if (ranges != null) {
            ranges.forEach(languageRange -> {
                final String localeString = languageRange.getRange();
                final Locale locale = Locale.forLanguageTag(localeString);
                acceptedLocales.add(locale);
            });
        }
    }
    return acceptedLocales;