You need to store the selected locale in the session scope and set it in the viewroot in two places: once by UIViewRoot#setLocale() immediately after changing the locale (which changes the locale of the current viewroot and thus get reflected in the postback; this part is not necessary when you perform a redirect afterwards) and once in the locale attribute of the <f:view> (which sets/retains the locale in the subsequent requests/views).
Here's an example how such a LocaleBean should look like:
package com.example.faces;
import java.util.Locale;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.context.FacesContext;
@ManagedBean
@SessionScoped
public class LocaleBean {
private Locale locale;
@PostConstruct
public void init() {
locale = FacesContext.getCurrentInstance().getExternalContext().getRequestLocale();
}
public Locale getLocale() {
return locale;
}
public String getLanguage() {
return locale.getLanguage();
}
public void setLanguage(String language) {
locale = new Locale(language);
FacesContext.getCurrentInstance().getViewRoot().setLocale(locale);
}
}
And here's an example of the view should look like:
<!DOCTYPE html>
<html lang="#{localeBean.language}"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html">
<f:view locale="#{localeBean.locale}">
<h:head>
<title>JSF/Facelets i18n example</title>
</h:head>
<h:body>
<h:form>
<h:selectOneMenu value="#{localeBean.language}" onchange="submit()">
<f:selectItem itemValue="en" itemLabel="English" />
<f:selectItem itemValue="nl" itemLabel="Nederlands" />
<f:selectItem itemValue="es" itemLabel="Espa?ol" />
</h:selectOneMenu>
</h:form>
<p><h:outputText value="#{text['some.text']}" /></p>
</h:body>
</f:view>
</html>
Note that <html lang> is not required for functioning of JSF, but it's mandatory how search bots interpret your page. Otherwise it would possibly be marked as duplicate content which is bad for SEO.
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