Example of using message resources in Spring Boot service layer code, in as simple way as possible (hopefully!). NOTE: this approach supports only a single locale, not dynamically changing it.

Messages.java

package com.company.project.components;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.MessageSource;
import org.springframework.context.support.MessageSourceAccessor;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import java.util.Locale;

/**
 * Helper to simplify accessing i18n messages in code.
 * 
 * This finds messages automatically found from src/main/resources (files named messages_*.properties)
 * 
 * This example uses hard-coded English locale.
 *
 * @author Joni Karppinen
 * @since 2015-11-02
 */
@Component
public class Messages {

    @Autowired
    private MessageSource messageSource;

    private MessageSourceAccessor accessor;

    @PostConstruct
    private void init() {
        accessor = new MessageSourceAccessor(messageSource, Locale.ENGLISH);
    }

    public String get(String code) {
        return accessor.getMessage(code);
    }

}

messages_en.properties

default.title = Title

SomeServiceImpl.java

package com.company.project.services;

import com.company.project.components.Messages;
import org.springframework.beans.factory.annotation.Autowired;

@Service
public class SomeServiceImpl implements SomeService {

    @Autowired
    Messages messages;
    
    // ... 
   
    private String getDefaultTitle() {
        return messages.get("default.title"));
    }

}

@kannangce, yes this one uses heard coded English as the locale value. If you have a spring-boot application just replace the Locale.ENGLISH with LocaleContextHolder.getLocale() and send the Accept-Language header.

If the locale specified in the accept-language value is not found then, it will fall back on classpath:src/main/resources/messages.properties file.

Have you tested this in an actual setup? My hunch said that this would always return the default locale and wouldn't dynamically change with the "Accept-Language" header simply because the construction of Components happens once at the start of the application when LocaleContextHolder.getLocale()) will return the default locale. Any later change of the Locale would have no effect on the already constructed Messages Component.

Tested this with a simple Spring Boot setup and confirmed my assumption above.

As far as I can see, this solution as it stands can only support a single Locale.

Thanks, very helpful and cleared up some confusion for me

But for my spring boot app, i still needed to over-ride the messageSource bean and set basename to messages

otherwise I get the "NoSuchMessageException"

@Bean
public ResourceBundleMessageSource messageSource() {
    ResourceBundleMessageSource messageSource = new ResourceBundleMessageSource();
    messageSource.addBasenames("messages");
    return messageSource;
}

LocaleContextHolder.getLocaleContext()

is it LocaleContextHolder.getLocale() instead?

Thanks! very helpfull

Im getting NullPointerException that MessageSource is null

Can you provide a simple unit test for this configuration? I cannot generate a dynamic locale change via this configuration.