code: @Override
  	public synchronized void register(final String key, final WComponent ui) {
  		if (isRegistered(key)) {
  			throw new SystemException("Cannot re-register a component. Key = " + key);
  		}
  
  		registry.put(key, ui);
  	}
docs: Registers the given user interface with the given key.
  
  @param key the registration key.
  @param ui the user interface to register.