public void setConnectTimeout(int connectTimeout) {
        if (connectTimeout <= 0) {
            throw new IllegalArgumentException("Illegal value of connection number [" + connNum
                                               + "], must be a positive integer].");
        }
        this.connectTimeout = connectTimeout;
    }
Get property value according to property key

@param key property key
@return property value
src/main/java/com/alipay/remoting/Url.java