Question

Framework: Spring, Hibernate. O/S: Windows

I am trying to implement hibernate’s Custom message interpolator following the direction of this Link.

When implementing the below class, it gives an error “Cannot make a static reference to the non-static type Locale”.

public class ClientLocaleThreadLocal<Locale> {
  private static ThreadLocal tLocal = new ThreadLocal();

  public static void set(Locale locale) {
    tLocal.set(locale);
  }

  public static Locale get() {
    return tLocal.get();
  }

  public static void remove() {
    tLocal.remove();
  } 

}

As I do not know generics enough, not sure how < Locale > is being used by TimeFilter class below and the purpose of definition in the above class.

public class TimerFilter implements Filter {
public void destroy() {
}

public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException {
    try {
        ClientLocaleThreadLocal.set(req.getLocale());       
        filterChain.doFilter(req, res);
    }finally {
        ClientLocaleThreadLocal.remove();
    }
}
public void init(FilterConfig arg0) throws ServletException {
}

}

Will doing the following be okay?

1. Change static method/field in ClientLocaleThreadLocal to non-static method/fields

2. In TimeFilter, set locale by instantiating new object as below.
   new ClientLocaleThreadLocal().set(req.getLocale())

Thanks for your help in advance

Answer 1

public class ClientLocaleThreadLocal<Locale>

declares a generic class ClientLocaleThreadLocal with a type parameter called Locale. Since the ClientLocaleThreadLocal always contains a Locale, there is no need for a type parameter here.

private static ThreadLocal tLocal = new ThreadLocal();

A ThreadLocal in contrast is a generic type, and has as type parameter the type of object it holds. In your case, this is Locale. Your code should therefore read:

public class ClientLocaleThreadLocal {
    private static ThreadLocal<Locale> tLocal = new ThreadLocal<Locale>();

As for what a ThreadLocal is, read its Javadoc or google its name.

Whether res.getLocale() is the “client locale” is something we can’t know, since “client locale” is a little vague.