Spring Boot Localization issue - Accept-Language h

We are using Spring Boot for the application. In ApplicationConfig.java I have the below code

 @Bean
    public LocaleResolver localeResolver() {
        return new SmartLocaleResolver();
    }

and the SmartLocaleResolver.java is below

public class SmartLocaleResolver extends SessionLocaleResolver {

    @Override
    public Locale resolveLocale(HttpServletRequest request) {
        final String acceptLanguage = request.getHeader("Accept-Language");
        if (acceptLanguage.contains(",")) {
            String[] aheader = acceptLanguage.split(",[ ]*");    
            for (String locale : aheader) {    
                if (ApplicationConstants.LOCALE.contains(locale)) {
                    locale.trim();
                    return Locale.forLanguageTag(locale);
                }
            }
        } else if (!acceptLanguage.contains(",") && !acceptLanguage.isEmpty()) {
            if (ApplicationConstants.LOCALE.contains(acceptLanguage)) {
                return Locale.forLanguageTag(acceptLanguage);
            }
        }
        return request.getLocale();
    }
}

and I have in my constants class the below to compare the value from header Accept-Language.

public static final List LOCALE = Collections .unmodifiableList(Arrays.asList("en", "es"));

I know in actual scenario the header will be like Accept-Language : fr,es;q=0.8,en-us;q=0.6 but for testing purpose i'm passing it as below.

Accept-language : fr,es,en

The code is not complete yet, but i'm just testing from postman to see if the code picks up "es" as the locale and gives me the localized result.

I don't have messages_fr.properties file but I have messages_es.properties so I expect if the application sets the locale from the below code, it would pick Locale as 'es' and give the values I want in Spanish. What changes I need to make here for the code to work?

The solution is:

public class SmartLocaleResolver extends AcceptHeaderLocaleResolver

instead of

public class SmartLocaleResolver extends SessionLocaleResolver

Below is the updated code:

import javax.servlet.http.HttpServletRequest;
import java.util.List;
import java.util.Locale;

import com.bbtransact.tss.api.commons.http.HttpConstants;
import org.apache.commons.lang.StringUtils;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;

public class SmartLocaleResolver extends AcceptHeaderLocaleResolver {
  @Override
  public Locale resolveLocale(HttpServletRequest request) {
     if (StringUtils.isBlank(request.getHeader("Accept-Language"))) {
         return Locale.getDefault();
       }
     List<Locale.LanguageRange> list = Locale.LanguageRange.parse(request.getHeader("Accept-Language"));
     Locale locale = Locale.lookup(list, ApplicationConstants.LOCALES);
      return locale;
     }
}

and in my constants class I have:

List<Locale> LOCALES = Arrays.asList(new Locale("en"),
                                         new Locale("es"),
                                         new Locale("fr"),
                                         new Locale("es", "MX"),
                                         new Locale("zh"),
                                         new Locale("ja"));