How to constrain to a set of locales?

answered 2019-02-26 18:14:36 +0800

cor3000
6280 ● 2 ● 7

The mechanism how ZK determines the current locale are described here:

https://www.zkoss.org/wiki/ZK%20Developer's%20Reference/Internationalization/Locale

You can choose any of the options described there, but as I understood you'd prefer a different solution a a lower level.

Obviously you could remove the language files directly from the jars - however that's not really nice.

At a lower level you can implement a ServletFilter and override the getLocale method using a ServletRequestWrapper

This allows you to limit the potential values returned by request.getLocale().

Here some untested code that how the ServletRequestWrapper can be used:

package zk.support.potential;

import javax.servlet.*;
import java.io.IOException;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;

public class RestrictLocaleFilter implements Filter {
    Set<Locale> allowedLocales = new HashSet<>();

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        //do some init here, e.g. read system properties or 
        //filter config parameter from web.xml
        allowedLocales.add(Locale.getDefault());
        allowedLocales.add(Locale.GERMAN);
        allowedLocales.add(Locale.FRENCH);
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, 
            FilterChain filterChain) throws IOException, ServletException {
        filterChain.doFilter(new ServletRequestWrapper(servletRequest) {
            @Override
            public Locale getLocale() {
                Locale requestedLocale = super.getLocale();
                if(allowedLocales.contains(requestedLocale)) {
                    return requestedLocale;
                } else {
                    return Locale.getDefault();
                }
            }
        }, servletResponse);
    }

    @Override
    public void destroy() { }
}