Spring REST Handle locale change - spring

Question

I'm trying to handle locale change in a Spring 3 REST application.
But the locale is not changed to fr.
The console log shows:
2014-05-19 14:29:46,214 DEBUG [AbstractExceptionHandler] locale: en
Here is my configuration:
#Bean
public MessageSource messageSource() {
ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
messageSource.setBasenames("classpath:messages/messages", "classpath:messages/validation");
// If true, the key of the message will be displayed if the key is not found, instead of throwing an exception
messageSource.setUseCodeAsDefaultMessage(true);
messageSource.setDefaultEncoding("UTF-8");
// The value 0 means always reload the messages to be developer friendly
messageSource.setCacheSeconds(0);
return messageSource;
}
// The locale interceptor provides a way to switch the language in any page just by passing the lang=’en’, lang=’fr’, and so on to the url
#Override
public void addInterceptors(InterceptorRegistry registry) {
LocaleChangeInterceptor localeChangeInterceptor = new LocaleChangeInterceptor();
localeChangeInterceptor.setParamName("lang");
registry.addInterceptor(localeChangeInterceptor);
}
#Bean
public LocaleResolver localeResolver() {
CookieLocaleResolver localeResolver = new CookieLocaleResolver();
localeResolver.setDefaultLocale(new Locale("en"));
return localeResolver;
}
Here is my exception handler:
#ControllerAdvice
public class AdminExceptionHandler extends AbstractExceptionHandler {
#ExceptionHandler(NullPointerException.class)
#ResponseBody
public ResponseEntity<ErrorInfo> nullPointerException(HttpServletRequest request, NullPointerException e) {
String url = request.getRequestURL().toString();
String errorMessage = localizeErrorMessage("error.npe", new Object[] { e.getMessage() });
return new ResponseEntity<ErrorInfo>(new ErrorInfo(url, errorMessage), HttpStatus.INTERNAL_SERVER_ERROR);
}
}
public class AbstractExceptionHandler {
private static Logger logger = LoggerFactory.getLogger(AbstractExceptionHandler.class);
#Autowired
private MessageSource messageSource;
protected String localizeErrorMessage(String errorCode, Object args[]) {
Locale locale = LocaleContextHolder.getLocale();
logger.debug("locale: " + locale);
return messageSource.getMessage(errorCode, args, locale);
}
protected String localizeErrorMessage(String errorCode) {
return localizeErrorMessage(errorCode, null);
}
protected String extractAdminIdFromUrl(String url) {
String adminId = null;
try {
URI uri = new URI(url);
String path = uri.getPath();
adminId = path.substring(path.lastIndexOf('/') + 1);
} catch (URISyntaxException e1) {
e1.printStackTrace();
}
return adminId;
}
}
And here is my test:
#Test
public void testExceptionLocalizedMessage() throws Exception {
HttpHeaders httpHeaders = Common.createAuthenticationHeaders("stephane" + ":" + PASSWORD);
MvcResult resultGet = this.mockMvc.perform(
get("/error/npe").headers(httpHeaders)
.param("lang", "fr")
.accept(MediaType.APPLICATION_JSON)
)
.andExpect(status().isInternalServerError())
.andExpect(jsonPath("$.message").value("Une erreur inconnue s'est produite. Veuillez nous excuser."))
.andReturn();
httpHeaders.add("Accept-Language", "fr");
resultGet = this.mockMvc.perform(
get("/error/npe").headers(httpHeaders)
.accept(MediaType.APPLICATION_JSON)
)
.andExpect(status().isInternalServerError())
.andExpect(jsonPath("$.message").value("Une erreur inconnue s'est produite. Veuillez nous excuser."))
.andReturn();
}
I would like to handle the locale argument in the url as in ?lang=en and the Accept-Language header as a fall back.
As a REST application I was thinking of using the AcceptHeaderLocaleResolver class but it does not support the setting of the locale via the url parameter.
I reckoned using the SessionLocaleResolver class makes little sense in a REST application.
That leaves my with the CookieLocaleResolver class which I'm not specially convinced is the one that should be used in a REST application.
Anyway, the retrieved locale is still en and not fr as I expect it to be.
EDIT:
In the test, using the statement:
httpHeaders.add("Accept-Language", Locale.FRENCH.getLanguage());
does not set the locale.
But using the locale() does.
This test passes:
this.mockMvc.perform(
get("/error/npe").headers(httpHeaders).locale(Locale.FRENCH)
.accept(MediaType.APPLICATION_JSON))
.andDo(print()
)
.andExpect(status().isInternalServerError())
.andExpect(jsonPath("$.message").value(localizeErrorMessage("error.npe", Locale.FRENCH)))
.andReturn();

Answer 1

I found the solution. Now the Accept-Language header is being used and the cookie as well.
public class WebConfiguration extends WebMvcConfigurerAdapter {
#Bean
public LocaleResolver localeResolver() {
return new SmartLocaleResolver();
}
}
public class SmartLocaleResolver extends CookieLocaleResolver {
#Override
public Locale resolveLocale(HttpServletRequest request) {
String acceptLanguage = request.getHeader("Accept-Language");
if (acceptLanguage == null || acceptLanguage.trim().isEmpty()) {
return super.determineDefaultLocale(request);
}
return request.getLocale();
}
}
UPDATE: Following Thor's comment, here is a resolver that checks first for the cookie, and if not found checks for the request header:
#Override
public Locale resolveLocale(HttpServletRequest request) {
Locale locale = super.determineDefaultLocale(request);
if (null == locale) {
String acceptLanguage = request.getHeader("Accept-Language");
if (acceptLanguage != null && !acceptLanguage.trim().isEmpty()) {
locale = request.getLocale();
}
}
return locale;
}
Or with a simpler implementation (not tested):
private AcceptHeaderLocaleResolver acceptHeaderLocaleResolver = new AcceptHeaderLocaleResolver();
#Override
public Locale resolveLocale(HttpServletRequest request) {
Locale locale = super.determineDefaultLocale(request);
if (null == locale) {
locale = acceptHeaderLocaleResolver.resolveLocale(request);
}
return locale;
}
UPDATE: This above solution is not working any longer.
I'm now trying to pass the accepted language in a header:
httpHeaders.add(HttpHeaders.ACCEPT_LANGUAGE, "fr_FR");
and retrieve it in this locale resolver:
#Override
public Locale resolveLocale(HttpServletRequest request) {
for (String httpHeaderName : Collections.list(request.getHeaderNames())) {
logger.debug("===========>> Header name: " + httpHeaderName);
}
String acceptLanguage = request.getHeader(HttpHeaders.ACCEPT_LANGUAGE);
logger.debug("===========>> acceptLanguage: " + acceptLanguage);
Locale locale = super.resolveLocale(request);
logger.debug("===========>> acceptLanguage locale: " + locale.getDisplayCountry());
if (null == locale) {
locale = getDefaultLocale();
logger.debug("===========>> Default locale: " + locale.getDisplayCountry());
}
return locale;
}
But there is no Accept-Language in the output of the ===========>> Header name logger, and the acceptLanguage logger is empty.

Answer 2

when we are using
#Bean
public SessionLocaleResolver localeResolver(){
SessionLocaleResolver localeResolver = new SessionLocaleResolver();
localeResolver.setDefaultLocale(Locale.US);
return localeResolver;
}
#Bean
public LocaleChangeInterceptor localeChangeInterceptor() {
LocaleChangeInterceptor localeChangeInterceptor = new LocaleChangeInterceptor();
localeChangeInterceptor.setParamName("language");
return localeChangeInterceptor;
}
it is able to accept locale from query parameter
{{url}}/com-manh-cp-ext-order/api/ext/ex23order/greeting?language=es