처음에는 AcceptHeaderLocaleResolver 로 한번 쿠키 설정된 이후로는 CookieLocaleResolver 로 동작하는 스프링 리졸버

CustomLocaleResolver.java

public class CustomLocaleResolver extends CookieLocaleResolver {

    public void setSupportedLocales(List<Locale> locales) {
        this.supportedLocales.clear();
        if (locales != null) {
            this.supportedLocales.addAll(locales);
        }
    }

    @Override
    public Locale resolveLocale(HttpServletRequest request) {
        Cookie cookie = WebUtils.getCookie(request, getCookieName());
        if (cookie == null) {
            Locale locale = request.getLocale();
            log.trace("request Locale : {}", locale);
            if (!isSupportedLocale(locale)){
                log.trace("not support single locale");
                Locale supportedLocale = findSupportedLocale(request);
                if(supportedLocale==null){
                    log.trace("not found any support lang");
                    return super.resolveLocale(request);
                }else{
                    log.trace("found support lang from locales : {}", locale);
                    request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME, locale);
                }
            }else{
                log.trace("support single locale : {} , {} ", locale ,LOCALE_REQUEST_ATTRIBUTE_NAME);
                request.setAttribute(LOCALE_REQUEST_ATTRIBUTE_NAME, locale);
            }
        }
        return super.resolveLocale(request);
    }


    private final List<Locale> supportedLocales = new ArrayList<Locale>(4);


    private boolean isSupportedLocale(Locale locale) {
        List<Locale> supportedLocales = getSupportedLocales();
        return (supportedLocales.isEmpty() || supportedLocales.contains(locale));
    }

    public List<Locale> getSupportedLocales() {
        return this.supportedLocales;
    }
  
    // 원래 스프링 코드와는 달리 지원안할 때는 null 로 처리
    private Locale findSupportedLocale(HttpServletRequest request) {
        Enumeration<Locale> requestLocales = request.getLocales();
        while (requestLocales.hasMoreElements()) {
            Locale locale = requestLocales.nextElement();
            if (getSupportedLocales().contains(locale)) {
                return locale;
            }
        }
        return null;
    }
}

WebConfig.java

@Bean
    public CookieLocaleResolver localeResolver() {
        CustomLocaleResolver resolver = new CustomLocaleResolver();
        resolver.setCookieName("testLocaleCookie");
        //  foo ba...
        resolver.setSupportedLocales(Arrays.asList(Locale.KOREA, Locale.ENGLISH));
        return resolver;
    }