code: public static void registerRequestHandler(RequestHandler<? extends Request> rh) {
  		if (rh == null) {
  			throw new NullPointerException("rh is null");
  		}
  
  		if (rh.handles() == null) {
  			throw new NullPointerException("rh.handles() returns null");
  		}
  
  		if (sRequestHandlers == null) {
  			initializeDefaultHandlers();
  		}
  
  		if (sRequestHandlers.containsKey(rh.handles())) {
  			throw new RuntimeException("RequestHandler already registered for "
  					+ rh.handles());
  		}
  
  		sRequestHandlers.put(rh.handles(), rh);
  	}
docs: Register a custom request handler.
  
  @param rh