Preferred Locale on AppFuse

The solution provided here are based on locale issues on AppFuse JIRA, specifically, APF-141 which is further refined in APF-142.

Here are the steps to change the request-based locale to user-preferred locale, i.e., implement a session-based locale on AppFuse:
1. Add session-scope PREFERRED_LOCALE and optional request scope DEFAULT_LOCALE constants.
2. Use LoginServlet to set locale session. The parameter, locale, is passed from loginForm.jsp, a selected locale from a dropdown for example.

public final class LoginServlet extends HttpServlet {
  ...
  public void execute(HttpServletRequest request, HttpServletResponse response)
  throws IOException, ServletException {
    ...
    request.getSession().setAttribute(Constants.PREFERRED_LOCALE, request.getParameter("locale"));
    ...
  }
}

3. Persist preferredLocale for user in ActionFilter:

public class ActionFilter implements Filter {
  public void doFilter(ServletRequest req, ServletResponse resp,
          FilterChain chain)
         throws IOException, ServletException {
    ...
    if ((username != null) && (user == null)) {
      ...
      String preferredLocale = session.getAttribute(Constants.PREFERRED_LOCALE).toString();
      if (preferredLocale != null) {
        if (preferredLocale  "") {
          if (user.getPreferredLocale()  null) {
                      user.setPreferredLocale(Constants.DEFAULT_LOCALE);
          }
        } else {
                  user.setPreferredLocale(preferredLocale);
        }
      }
    }      
    session.setAttribute(Constants.PREFERRED_LOCALE, user.getPreferredLocale());
  }
}

4. Add locale filter, LocaleFilter:

public class LocaleFilter implements Filter {
  private static final transient Log log = LogFactory.getLog(LocaleFilter.class);
  public void init(FilterConfig filterConfig) {
  }

  public void destroy() {
  }
  public void doFilter(ServletRequest request, ServletResponse response,
                                      FilterChain chain)
           throws IOException, ServletException {
      HttpServletRequest servletRequest = (HttpServletRequest) request;
      HttpSession session = servletRequest.getSession(false);

      if (log.isDebugEnabled()) {
          log.debug(servletRequest.getRequestURL());
      }
      Locale preferredLocale = null;

      if (session!=null){          
          if (session.getAttribute(Constants.PREFERRED_LOCALE) != null) {
              String localeKey = session.getAttribute(Constants.PREFERRED_LOCALE).toString();
              if (localeKey != null) {
                  if (localeKey.equals("")) {
                      String[] keys = Constants.DEFAULT_LOCALE.split("-");
                      preferredLocale = new Locale(keys[0],keys[1]);
                  } else {
                      String[] keys = localeKey.split("-");
                      preferredLocale = new Locale(keys[0],keys[1]);
                  }
              }    
          }
      }
      if (null != preferredLocale
              && !(request instanceof LocaleResponseWrapper)) {
          request = new LocaleResponseWrapper(servletRequest, preferredLocale);
      }

      chain.doFilter(request, response);
   }
}

5. The associated LocaleResponseWrapper is equivalent to LocaleRequestWrapper:

public class LocaleResponseWrapper extends HttpServletRequestWrapper {
  private final Locale preferredLocale;
  private Enumeration locales;

  public LocaleResponseWrapper(HttpServletRequest request, Locale sessionLocale) {
       super(request);
       preferredLocale = sessionLocale;
  }

  public Locale getLocale() {
      if (null != preferredLocale) {
          return preferredLocale;
      } else {
          return super.getLocale();
      }
  }
  public Enumeration getLocales() {
      if (null != preferredLocale) {
          return setLocales();
      } else {
          return super.getLocales();
      }
  }
  private Enumeration setLocales() {
      if (null == locales) {
          List l = Collections.list(super.getLocales());
          l.add(0, preferredLocale);
          locales = Collections.enumeration(l);
      }
      return locales;
  }
} 

6. Put the locale filter in web.xml or appfuse/metadata/web/filters.xml:

<filter>
  <filter-name>localeFilter</filter-name>
  <display-name>Locale Filter</display-name>
  <filter-class>org.appfuse.webapp.filter.LocaleFilter</filter-class>
</filter>

7. Modify JSP’s: add page-scope locale setting:

<fmt:setLocale value="${preferredLocale}" /> 

Now AppFuse is powered by preferred locale! 
¶ 9:41 AM