Spring framework: No message found under code for locale

For spring boot you need something like this:

@Bean
public MessageSource messageSource() {
     ReloadableResourceBundleMessageSource messageSource = new ReloadableResourceBundleMessageSource();
     messageSource.setBasename("/WEB-INF/classes/messages");
     return messageSource;
}

In general such issue appears not because of non-existence locale, but because MessageBundle is configured improperly. In your case you seem to need to remove "/" in your basename.

<bean id="messageSource"
     class="org.springframework.context.support.ReloadableResourceBundleMessageSource"
     p:basename="/WEB-INF/messages" />

Why it is so:

If you have messages.properties and messages_en.properties bundle, then bundle name is messages. If you have them in the WEB-INF folder, then basename is /WEB-INF/messages, i.e. according to /path/to/bundle/bundlename. If you have messages.properties within /WEB-INF/messages folder, then corresponding basename is /WEB-INF/messages/messages.