Defining MessageSource and LocaleResolver beans in Spring MVC for adding i18n support

Question

I'm trying to add i18n support to a Spring MVC project(3.2.0.RELEASE). I have two bundles below /src/main/resources/bundle:

messageBundle_en.properties
messageBundle_vi.properties

And the configurations for spring mvc as below:

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="cache" value="false" />
    <property name="prefix" value="/WEB-INF/jsp/" />
    <property name="suffix" value=".jsp" />
</bean>

<bean class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
    <property name="basename" value="classpath:bundle/messageBundle" />
</bean>
<bean class="org.springframework.web.servlet.i18n.CookieLocaleResolver">
    <property name="defaultLocale" value="vi" />
</bean>
<mvc:interceptors>
    <bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
        <property name="paramName" value="lang" />
    </bean>
</mvc:interceptors>

with above configurations the application is not working. The error was

org.apache.jasper.JasperException: javax.servlet.ServletException: javax.servlet.jsp.JspTagException: No message found under code 'message.home.header.welcome' for locale 'en_US'.
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:549)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:455)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)

I spent many hours comparing with tutorials of adding i18n support. I saw that there is only one difference: bean definitions of CookieLocaleResolver and ReloadableResourceBundleMessageSource have id attributes. So I changed the configurations to

<bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
    <property name="basename" value="classpath:bundle/messageBundle" />
</bean>
<bean id="localeResolver" class="org.springframework.web.servlet.i18n.CookieLocaleResolver">
    <property name="defaultLocale" value="vi" />
</bean>

Now it's working well!

Do ReloadableResourceBundleMessageSource and CookieLocaleResolver require to have ids in their definitions?

Why doesn't InternalResourceViewResolver need an id?

Wondering if anyone can give me an explanation in details.

Solution

DispatcherServlet.java

public static final String LOCALE_RESOLVER_BEAN_NAME = "localeResolver";

private void initLocaleResolver(ApplicationContext context) {
    try {
        this.localeResolver = context.getBean(LOCALE_RESOLVER_BEAN_NAME, LocaleResolver.class);
        if (logger.isDebugEnabled()) {
            logger.debug("Using LocaleResolver [" + this.localeResolver + "]");
        }
    }
    catch (NoSuchBeanDefinitionException ex) {
        // We need to use the default.
        this.localeResolver = getDefaultStrategy(context, LocaleResolver.class);
        if (logger.isDebugEnabled()) {
            logger.debug("Unable to locate LocaleResolver with name '" + LOCALE_RESOLVER_BEAN_NAME +
                    "': using default [" + this.localeResolver + "]");
        }
    }
}

Spring uses some conventional bean name to intialize DispatcherServlet.

In your case, spring will use a default one if no bean named "localeResolver" is found (therefore your custom LocaleResover is ignored).

UPDATE

In messageSource case,

"When an ApplicationContext is loaded, it automatically searches for a MessageSource bean defined in the context. The bean must have the name messageSource. If such a bean is found, all calls to the preceding methods are delegated to the message source. If no message source is found, the ApplicationContext attempts to find a parent containing a bean with the same name. If it does, it uses that bean as the MessageSource. If the ApplicationContext cannot find any source for messages, an empty DelegatingMessageSource is instantiated in order to be able to accept calls to the methods defined above."

quoted from spring doc.

Comments

[Martin Frey]

The same counts for messageSource. Spring fetches it by name.

[Tuna]

messageSource is initialized in AbstractApplicationContext.java