code: protected URL isProxied(URI uri) throws MalformedURLException
      {
          // Is this a proxy request?
          if (isForbidden(uri))
              return null;
  
          // OK return URI as untransformed URL.
          return new URL(uri.toString());
      }
docs: Is URL Proxied. Method to allow derived handlers to select which URIs are proxied and to
  where.
  
  @param uri The requested URI, which should include a scheme, host and port.
  @return The URL to proxy to, or null if the passed URI should not be proxied. The default
  implementation returns the passed uri if isForbidden() returns true.