public static Integer getInteger(final String key) {
        String value = System.getProperty(key, null);
        return value != null ? Integer.parseInt(value) : null;
    }
get configs through system properties prior to default value

@author tsui
@version $Id: ConfigManager.java, v 0.1 2017-08-03 19:21 tsui Exp $
src/main/java/com/alipay/remoting/config/ConfigManager.java