i18n

package az.etibarli.i18n.config;

import org.springframework.context.MessageSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.support.ResourceBundleMessageSource;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;
import org.springframework.web.servlet.LocaleResolver;
import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;

import java.util.Arrays;
import java.util.Locale;

@Configuration
public class I18nConfig {

    private static final Locale LOCALE_AZ = Locale.of("az");
    private static final Locale LOCALE_EN = Locale.of("en");
    private static final Locale LOCALE_RU = Locale.of("ru");

    @Bean
    public MessageSource messageSource() {
        ResourceBundleMessageSource resourceBundleMessageSource = new ResourceBundleMessageSource();
        resourceBundleMessageSource.setBasename("i18n/messages");
        resourceBundleMessageSource.setDefaultEncoding("UTF-8");
        resourceBundleMessageSource.setUseCodeAsDefaultMessage(true);
        return resourceBundleMessageSource;
    }

    @Bean
    public LocaleResolver localeResolver() {
        AcceptHeaderLocaleResolver localeResolver = new AcceptHeaderLocaleResolver();
        localeResolver.setDefaultLocale(LOCALE_RU);
        localeResolver.setSupportedLocales(Arrays.asList(LOCALE_AZ, LOCALE_EN, LOCALE_RU));
        return localeResolver;
    }

} 

package az.etibarli.i18n.config;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.MessageSource;
import org.springframework.context.NoSuchMessageException;
import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.stereotype.Component;

@Slf4j
@Component
@RequiredArgsConstructor
public class MessageSourceUtil {

    private final MessageSource messageSource;

    public String getMessage(String key, Object... args) {
        final var locale = LocaleContextHolder.getLocale();
        try {
            return messageSource.getMessage(key, args, locale);
        } catch (NoSuchMessageException ex) {
            log.warn("Could not find message for key '{}' and locale '{}'", key, locale, ex);
        }
        return key;
    }

}

package az.etibarli.i18n.exception;

import static az.etibarli.i18n.config.ErrorMessageAttribute.ALREADY_EXISTS;

public class NotFoundException extends RuntimeException {

    public NotFoundException() {
        super(ALREADY_EXISTS);
    }

}

package az.etibarli.i18n.exception;

import az.etibarli.i18n.config.MessageSourceUtil;
import lombok.RequiredArgsConstructor;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
@RequiredArgsConstructor
public class GlobalExceptionHandler {

    private final MessageSourceUtil messageSourceUtil;

    @ExceptionHandler(NotFoundException.class)
    public ResponseEntity<Object> handleNotFoundException(NotFoundException ex) {
        String message = messageSourceUtil.getMessage(ex.getMessage());
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(message);
    }

}