code: protected String getResourceBundleString(String key) {
          ResourceBundle rb = getResourceBundle();
          // This is one of the rare cases where we can use logging in order
          // to report errors from within log4j.
          if (rb == null) {
              // if(!hierarchy.emittedNoResourceBundleWarning) {
              // error("No resource bundle has been set for category "+name);
              // hierarchy.emittedNoResourceBundleWarning = true;
              // }
              return null;
          } else {
              try {
                  return rb.getString(key);
              } catch (MissingResourceException mre) {
                  error("No resource is associated with key \"" + key + "\".");
                  return null;
              }
          }
      }
docs: Returns the string resource coresponding to <code>key</code> in this category's inherited resource bundle. See also
  {@link #getResourceBundle}.
  
  <p>
  If the resource cannot be found, then an {@link #error error} message will be logged complaining about the missing resource.