Using Spring IoC to set up enum values

Question

Is there a way to set up such enum values via Spring IoC at construction time?

What I would like to do is to inject, at class load time, values that are hard-coded i

Answer 1

I have faced the same issue when I was working to localize my enum label in different locales.

Enum Code:

public enum Type {
   SINGLE("type.single_entry"),
   MULTIPLE("type.multiple_entry"),
   String label;

   Type(String label) {
     this.label = label;
   }

   public String getLabel() {
     String translatedString = I18NTranslator.getI18NValue(getLocale(), label);
     return StringUtils.isEmpty(translatedString) ? label : translatedString;
   }
}

My I18NTranslator class which basically load the message source to get localized content. I18Ntransalator class depends on springContext if you don't write you might face a peculiar bug. Some time might face a dependency related which causes null pointer exception. I had put a lot of effort to resolve this issue.

@Component
@DependsOn({"springContext"})
public class I18NTranslator {

    private static MessageSource i18nMessageSource;

    public static String getI18NValue(Locale locale, String key) {
        if (i18nMessageSource != null)
            return i18nMessageSource.getMessage(key, null, locale);
        return key;
    }

    @PostConstruct
    public void initialize() {
        i18nMessageSource = SpringContext.getBean("i18nMessageSource", MessageSource.class);
    }
}

We have to set the spring context

@Component
@Slf4j
public class SpringContext implements ApplicationContextAware {

    private static ApplicationContext context;

    public static  T getBean(Class beanClass) {
        return context.getBean(beanClass);
    }

    public static  T getBean(String beanClassName, Class beanClass) {
        return context.getBean(beanClassName, beanClass);
    }

    @Override
    public void setApplicationContext(ApplicationContext context) throws BeansException {
        SpringContext.context = context;
    }
}

Now it is time to define the bean for I18NMessageSource.

@Configuration
public class LocaleConfiguration implements WebMvcConfigurer {

    @Bean(name = "i18nMessageSource")
    public MessageSource getMessageResource() {
        ReloadableResourceBundleMessageSource messageResource = new ReloadableResourceBundleMessageSource();
        messageResource.setBasename("classpath:i18n/messages");
        messageResource.setCacheSeconds(3600);
        messageResource.setDefaultEncoding("UTF-8");
        return messageResource;
    }

    @Bean(name = "localeResolver")
    public LocaleResolver getLocaleResolver() {
        return new UrlLocaleResolver();
    }

    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //UrlLocalInterceptor is custom locale resolver based on header paramter.
        UrlLocaleInterceptor localeInterceptor = new UrlLocaleInterceptor();
        registry.addInterceptor(localeInterceptor);
    }
}

PS: if you need the custom interceptor code I can share in the comment. Defines all local properties files inside resources/i18n folder with messages prefix like messages_en.properties for english and messages_fr.properties fro french.