Transparent web-app I18N - WebWork

As of WebWork 2.2, this interceptor is included with the normal distribution as the I18n Interceptor

Consider adding transparent i18 with simple on-the-fly locale switching to your appliction via I18NInterceptor.

The main idea:
Interceptor could track locale switch requests, persist selection in current session and set locale for all (or appropriate) actions invoked.

package neuro.util.xwork;

import com.opensymphony.xwork.ActionSupport;
import com.opensymphony.xwork.ActionInvocation;
import com.opensymphony.xwork.interceptor.Interceptor;

import java.util.Locale;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * I18nInterceptor
 * @author Aleksei Gopachenko
 */
public class I18nInterceptor implements Interceptor
{
    protected static final Log log = LogFactory.getLog(I18nInterceptor.class);

    public static final String DEFAULT_SESSION_ATTRIBUTE = "WW_TRANS_I18N_LOCALE";
    public static final String DEFAULT_PARAMETER = "request_locale";

    protected String parameterName = DEFAULT_PARAMETER;
    protected String attributeName = DEFAULT_SESSION_ATTRIBUTE;

    /**
     */
    public I18nInterceptor()
    {
        if(log.isDebugEnabled()) log.debug("new I18nInterceptor()");
    }

    public void setParameterName(String parameterName) {
        this.parameterName = parameterName;
    }

    public void setAttributeName(String attributeName) {
        this.attributeName = attributeName;
    }

    /**
     */
    public void init() {
        if(log.isDebugEnabled()) log.debug("init()");
    }

    /**
     */
    public void destroy() {
        if(log.isDebugEnabled()) log.debug("destroy()");
    }

    /**
     */
    public String intercept(ActionInvocation invocation) throws Exception {
        if(log.isDebugEnabled()) log.debug("intercept '"
            +invocation.getProxy().getNamespace()+"/"
            +invocation.getProxy().getActionName()+"' { ");

        //get requested locale
        Object requested_locale = invocation.getInvocationContext().getParameters().get(parameterName);
        if(requested_locale!=null && requested_locale.getClass().isArray() && ((Object[])requested_locale).length==1) {
            requested_locale=((Object[])requested_locale)[0];
        }
        if(log.isDebugEnabled()) log.debug("requested_locale="+requested_locale);
        //save it in session
        if (requested_locale!=null) {
            Locale locale = (requested_locale instanceof Locale)? 
              (Locale) requested_locale : localeFromString(requested_locale.toString());
            if(log.isDebugEnabled()) log.debug("store locale="+locale);
            if(locale!=null)invocation.getInvocationContext().getSession().put(attributeName,locale);
        }
        //set locale for action
        Object locale = invocation.getInvocationContext().getSession().get(attributeName);
        if (locale!=null && locale instanceof Locale) {
            if(log.isDebugEnabled()) log.debug("apply locale="+locale);
            invocation.getInvocationContext().setLocale((Locale)locale);
        }

        if(log.isDebugEnabled()) log.debug("before Locale="+((ActionSupport)invocation.getAction()).getLocale());
        final String result = invocation.invoke();
        if(log.isDebugEnabled()) log.debug("after Locale="+((ActionSupport)invocation.getAction()).getLocale());

        if(log.isDebugEnabled()) log.debug("intercept } ");
        return result;
    }

    Locale localeFromString(String localeStr) {
        if ((localeStr == null) || (localeStr.trim().length() == 0) || (localeStr.equals("_"))) {
            return Locale.getDefault();
        }
        int index = localeStr.indexOf('_');
        if (index < 0) {
            return new Locale(localeStr);
        }
        String language = localeStr.substring(0,index);
        if (index == localeStr.length()) {
            return new Locale(language);
        }
        localeStr = localeStr.substring(index +1);
        index = localeStr.indexOf('_');
        if (index < 0) {
            return new Locale(language,localeStr);
        }
        String country = localeStr.substring(0,index);
        if (index == localeStr.length()) {
            return new Locale(language,country);
        }
        localeStr = localeStr.substring(index +1);
        return new Locale(language,country,localeStr);
    }

}

Can be enabled for whole package via something like:

<interceptor name="i18n" class="neuro.util.xwork.I18nInterceptor">
    <!-- on which request parameter we should react, optional, defaults to "request_locale" ->
    <param name="parameterName">set_locale</param>
    <!- under which session attribute locale should be stored, optional, defaults to "WW_TRANS_I18N_LOCALE" ->
    <param name="attributeName">ww_locale</param>
</interceptor>

<interceptor-stack name="i18nStack">
    <interceptor-ref name="i18n"/>
    <interceptor-ref name="defaultStack"/>
</interceptor-stack>

<default-interceptor-ref name="i18nStack"/>

...and invoked in web-app just by adding few links to menu:

<a href="?set_locale=en">EN</a>
<a href="?set_locale=ru">RU</a>
<!- etc -->

Of course you still need to move all explisitly defined messages or labels to appropriate ResourceBundles and make translations. Be sure to check out your

Actions - to use getText(...)
*-validation.xml files - to use <message key=...>
results/views - to use WW i18n services by <webwork:text ...> tag, or directly by evaluating getText(...) OGNL expression on current stack.

If this Interceptor is generally useful, may be it should go into codebase?