Create custom LocalChangeInterceptor - spring

Question

I am writing an application using Spring Boot. In my application I am going to use localized URL smth like http://localhost:8080/School/**en**/xxx/... . I try to implement Custom Locale Interceptor. In listing below the first variant works fine. I would like to use the second variant but instead of France or Germany locale doesn't change and remains en_US. Can anybody please suggest me anything ?
#Configuration
public class WebConfiguration extends WebMvcConfigurerAdapter {
1 VARIANT
#Bean
public LocaleResolver localeResolver() {
SessionLocaleResolver slr = new SessionLocaleResolver();
slr.setDefaultLocale(Locale.GERMANY);
return slr;
}
#Bean
public LocaleChangeInterceptor localeChangeInterceptor() {
LocaleChangeInterceptor lci = new LocaleChangeInterceptor();
lci.setParamName("lang");
return lci;
}
#Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(localeChangeInterceptor());
}
2 VARIANT
#Bean
public LangInterceptor langInterceptor() {
return new LangInterceptor();
}
#Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor( langInterceptor());
}
#Bean
public SessionLocaleResolver sessionLocaleResolver() {
SessionLocaleResolver sessionLocaleResolver = new SessionLocaleResolver();
sessionLocaleResolver.setDefaultLocale(Locale.GERMANY);
return sessionLocaleResolver;
}
}
And my custom Interceptor:
public class LangInterceptor extends HandlerInterceptorAdapter {
#Autowired
LocaleResolver sessionLocaleResolver;
Locale locale;
#Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
if (StringUtils.startsWithIgnoreCase(request.getServletPath(), "/it/")) {
locale = new Locale("it");
} else {
locale = new Locale("en");
}
sessionLocaleResolver.setLocale(request, response, Locale.FRENCH);
return true;
}
#Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
}
#Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
}
}

Answer 1

You can't throw in a random HandlerInterceptorAdapter to change the locale. Spring uses AcceptHeaderLocaleResolver by default and you want to resolve based on path segment. Extend WebMvcConfigurerAdapter, then do the following:
#Bean
public LocaleResolver localeResolver() {
// return custom LocaleResolver
}
However, I'm cautioning you that you're going against the HTTP spec. The Accept-Language header is meant for this purpose, which is what the AcceptHeaderLocaleResolver uses.
You don't need a LocaleChangeInterceptor because it operates on a query parameter.

Answer 2

I found the solution. First variant will work if I just add in my configuration file LocaleChangeInterceptor. The reason looks like LocaleResolver doesn't initialize without interceptor, but spring docs says that every class has default constructor. So it works.
#Bean
public LocaleChangeInterceptor localeChangeInterceptor() {
LocaleChangeInterceptor lci = new LocaleChangeInterceptor();
lci.setParamName("lang");
return lci;
}