code: protected void fireCommandRegistered(AbstractCommand command) {
          
          Assert.notNull(command, "command");
          
          if (commandRegistryListeners.isEmpty()) {
              return;
          }
          
          CommandRegistryEvent event = new CommandRegistryEvent(this, command);
          
          for (Iterator i = commandRegistryListeners.iterator(); i.hasNext();) {
              ((CommandRegistryListener)i.next()).commandRegistered(event);
          }
          
      }
docs: Fires a 'commandRegistered' {@link CommandRegistryEvent} for the given command to all
  registered listeners.
  
  @param command The command that has been registered. Must not be null.
  
  @throws IllegalArgumentException if {@code command} is null.