Where to place i18n key strings in Java

Question

When doing internationalization in Java, you assign a string key to each message. What\'s the best practice, on where to place those string keys. Goal is to allow easy refactori

Answer 1

I've devised this method long time ago for the shortest amount of typing necessary to get localized version of given strings and to easily add new entries as well. I think it is useful for many type of Java projects as well.

1. An enum class ME (Short for MessagesEnum) has all the definitions and its constructor converts LOREM_IPSUM to lorem.ipsum so that you don't have to type constructor parameter.

2. An I18NManager class which is responsible for getting the Locale from the context and constructing/caching ResourceBundles, preferably a Spring @Component.

3. An optional ServiceRegistry class for static access to I18NManager instance, from ME.get() method to complete the cycle.

The enum:

public enum ME {

    USERNAME,
    PASSWORD,
    LOGIN,
    LOGOUT,
    DASHBOARD,
    MENU,
    OK,
    CANCEL,
    YES,
    NO,
    CONFIRM,
    DELETE,
    CREATE,
    NEW,
    EDIT,
    ONLINE,
    OFFLINE,
    SALES_REPORTS,
    ...;

    private String key;

    ME(String key){
        this.key = key;
    }

    ME(){
        this.key = name().toLowerCase(Locale.ENGLISH).replace("_", ".");
    }

    public String get(){
        return ServiceRegistry.get().getI18nManager().getMessage(key);
    }

    public String get(Object ...args ){
        return ServiceRegistry.get().getI18nManager().getMessage(key, args);
    }

    public String key(){
        return key;
    }

}

I18NManager:

import java.text.MessageFormat;
import java.util.Locale;
import java.util.ResourceBundle;

public interface I18nManager {

    Locale getCurrentUserLocale();

    ResourceBundle getResourceBundle(Locale locale);

    default String getMessage(String key) {
        return getResourceBundle(getCurrentUserLocale()).getString(key); //FIXME add error handling
    }

    default String getMessage(String key, Object... args) {
        return MessageFormat.format(getMessage(key), args);
    }
}

Usage is simply:

ME.SALES_REPORTS.get()