public String cmd(List<String> configs, List<List<String>> cfgParams, List<String> params) {
		if (null == this.handler) {
			throw new LackOfHandlerException();
		}

		if (configs.size() != cfgParams.size()) {
			throw new LackOfParamsException();
		}
		
		int index = 0;
		for (String cfg : configs) {
			Config config = this.configs.get(cfg);
			if (null == config) {
				System.err.println(String.format("lack of config, %s", cfg));
			}
			config.cfg(cfgParams.get(index++), handler);
		}
		
		return this.handler.fn(params);
	}