Spring - I18n - Access MessageSource over static class?

Question

I followed some tutorials like this one:

http://www.concretepage.com/spring-4/spring-4-mvc-internationalization-i18n-and-localization-l10n-annotation-example

to get i18n work in my spring(boot) project. It's working so far, but I don't like it to always autowire the MessageSource bean to my current class, just to get some Strings translated.

My idea is a easy wrapper class with a static call like

I18n.translate("some.identifier") 

or

I18n.translate("some.identifier",param,param,param...).

But I can't inject the MessageSource into a class which is not handled by Spring, huh?

Any idea how to solve this?

Answer 1

You could (not sure if you should) do something like this:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;

@Component
public class StaticContextAccessor {

    private static StaticContextAccessor instance;

    @Autowired
    private ApplicationContext applicationContext;

    @PostConstruct
    public void registerInstance() {
        instance = this;
    }

    public static <T> T getBean(Class<T> clazz) {
        return instance.applicationContext.getBean(clazz);
    }

}

and then use it like this:

SomeOtherwiseAutowiredClass someObject = StaticContextAccessor.getBean(SomeOtherwiseAutowiredClass.class);

Answer 2

I had the same Idea as I develop also with Vaadin and the solution which works for me is to use a StaticContextInitializer Bean. Therefore do the following:

First make your field for the Message class static and provide the getter and setter methods:

private static MessageSource messageSource;

private TextSource() {
}

public static String getText(String key, Locale locale) {
    return messageSource.getMessage(key,null, ensureLocale(locale));
}



public static String getText(String key, Locale locale, Object[] parameter) {
    return messageSource.getMessage(key, parameter, ensureLocale(locale));
}

private static Locale ensureLocale(Locale locale) {
    if (locale == null)
        locale = Locale.getDefault();
    return locale;
}

Add the static setter method to the class:

public static void setMessageSource(MessageSource messageSource) {
    TextSource.messageSource = messageSource;
}

Write your StaticInitializer Bean with a @PostConstruct annotation and inject the MessageSource with @Autowired annotation.

@Component
public class FrontendStaticContextInitializer {

@Autowired
private MessageSource messageSource;

@PostConstruct
public void initialize() {
    TextSource.setMessageSource(messageSource);
}
}

After that you'll be able to call the class like that in your Views: TextSource.getText("login.textfield.placeholder.benutzername", getLocale())

Answer 3

You have two possibilities:

1. Non-static setter for static property/field;
2. Using org.springframework.beans.factory.config.MethodInvokingFactoryBean to invoke a static setter.

Examples you can find follow by link How to make spring inject value into a static field

P.S. What is problem with autowire MessageSource into your beans?

Answer 4

Create a static message source wrapper, for example like https://github.com/chelu/jdal/blob/master/core/src/main/java/org/jdal/beans/StaticMessageSource.java

and declare it in bean configuration file:

<!-- Message Source -->
<bean id="messageSource"
        class="org.springframework.context.support.ResourceBundleMessageSource">
    <property name="basenames" value="i18n/jdal,i18n/i18n" />
</bean>

<bean id="staticMessageSource" class="org.jdal.beans.StaticMessageSource">
        <constructor-arg ref="messageSource" />
</bean>

Note that you can use depend-on if you need that the wrapper is instantiated before some other bean.

Answer 5

Just implement MessageSourceAware and set it to the static variable. But, it will only work if spring.main.lazyInitialization is false.

@Component
public final class MessageUtils implements MessageSourceAware {

    private static MessageSource messageSource;

    @Override
    public void setMessageSource(MessageSource messageSource) {
        MessageUtils.messageSource = messageSource;
    }

    public static String getMessage(String key, String... params) {
        return messageSource.getMessage(key, params, new Locale("PT", "br"));
    }

}

If spring.main.lazyInitialization is true, will need to force the injection:

public class App {

    @Autowired
    private MessageUtils messageUtils;

    public static void main(String[] args) {
        SpringApplication.run(App .class, args);
    }

}

Spring will automatically inject, see class: ApplicationContextAwareProcessor.invokeAwareInterfaces(Object bean)

Answer 6

here is a sample Utils, without DI concept, without Bean configuration:

import java.util.Locale;

import org.apache.commons.lang3.Validate;
import org.springframework.context.MessageSource;
import org.springframework.context.support.ReloadableResourceBundleMessageSource;

public class I18n {
    private static MessageSource MESSAGE_SOURCE;
    static {
        I18nUtils.MESSAGE_SOURCE = messageSource();
    }

    public static String translate(Locale locale, String key, Object... args) {
        Validate.notNull(locale, "locale require not null");
        Validate.notEmpty(key, "key require not empty");
        return MESSAGE_SOURCE.getMessage(key, args, locale);
    }

    private static MessageSource messageSource() {
        ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
        messageSource.addBasenames("classpath:Messages");
        messageSource.setDefaultEncoding("UTF-8");
        return messageSource;
    }
}