Restrictive locale resolver

If you make a web application that supports several languages with Spring you are definitely familiar with the handy locale resolvers Spring provides. Unfortunately, none of them allows to restrict the number of locales that can be set. We needed such restriction, because some of our database queries depended on the locale. So I wrote a wrapper locale resolver for it:

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
import org.springframework.web.servlet.LocaleResolver;
 
/**
 * A wrapper for LocaleResolver. Allows to set only one of the predefined set of locales.
 *
 * @author Ilya Boyandin
 */
public class RestrictiveLocaleResolver implements LocaleResolver {
 
	private final LocaleResolver localeResolver;
	private final Locale defaultLocale;
	private final List<Locale> supportedLocales;
 
	private RestrictiveLocaleResolver(
			LocaleResolver localeResolver, Locale defaultLocale,
			Collection<String> supportedLocales) {
 
		this.localeResolver = localeResolver;
		this.defaultLocale = defaultLocale;
 
		final List<Locale> locales = new ArrayList<Locale>();
		for (String loc : supportedLocales) {
			locales.add(new Locale(loc));
		}
		this.supportedLocales = locales;
	}
 
	public LocaleResolver getLocaleResolver() {
		return localeResolver;
	}
 
	public Locale getDefaultLocale() {
		return defaultLocale;
	}
 
	public Collection<Locale> getSupportedLocales() {
		return Collections.unmodifiableCollection(supportedLocales);
	}
 
	@Override
	public Locale resolveLocale(HttpServletRequest request) {
		final Locale resolved = localeResolver.resolveLocale(request);
		final Locale supported = findSupportedLocale(resolved);	 // this ensures that a locale with one
																 // of the predefined names will be used
		if (supported != null) {
			return supported;
		} else {
			return defaultLocale;
		}
	}
 
	@Override
	public void setLocale(HttpServletRequest request, HttpServletResponse response, Locale locale) {
		final Locale supported = findSupportedLocale(locale);	// this ensures that a locale with one
																// of the predefined names will be used
		if (supported != null) {
			localeResolver.setLocale(request, response, supported);
		} else {
			localeResolver.setLocale(request, response, defaultLocale);
		}
	}
 
	private Locale findSupportedLocale(Locale locale) {
		for (int i = 0, len = supportedLocales.size(); i < len; i++) {
			final Locale loc = supportedLocales.get(i);
			if (loc.equals(locale)) return loc;
		}
		return null;
	}
 
}

And then you must have something like this in your config file (of course, you can use any other locale resolver instead of SessionLocaleResolver here):

<bean id="localeResolver" class="org.fhj.joanna.web.utils.RestrictiveLocaleResolver">
	<constructor-arg><bean class="org.springframework.web.servlet.i18n.SessionLocaleResolver"/></constructor-arg>
	<constructor-arg value="de"/>
	<constructor-arg><set><value>de</value><value>en</value></set></constructor-arg>
</bean>

This entry was posted on Saturday, September 15th, 2007 at 8:14 pm and is filed under java, spring. You can follow any comments to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site.

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