@Override
    public String telnet(Channel channel, String message) {
        if (StringUtils.isEmpty(message)) {
            return "Please input service name, eg: \r\ncd XxxService\r\ncd com.xxx.XxxService";
        }
        StringBuilder buf = new StringBuilder();
        if ("/".equals(message) || "..".equals(message)) {
            String service = (String) channel.getAttribute(SERVICE_KEY);
            channel.removeAttribute(SERVICE_KEY);
            buf.append("Cancelled default service ").append(service).append('.');
        } else {
            boolean found = false;
            for (Exporter<?> exporter : DubboProtocol.getDubboProtocol().getExporters()) {
                if (message.equals(exporter.getInvoker().getInterface().getSimpleName())
                        || message.equals(exporter.getInvoker().getInterface().getName())
                        || message.equals(exporter.getInvoker().getUrl().getPath())) {
                    found = true;
                    break;
                }
            }
            if (found) {
                channel.setAttribute(SERVICE_KEY, message);
                buf.append("Used the ")
                        .append(message)
                        .append(" as default.\r\nYou can cancel default service by command: cd /");
            } else {
                buf.append("No such service ").append(message);
            }
        }
        return buf.toString();
    }
@Test
    void testChangeCancel() throws RemotingException {
        String result = change.telnet(mockChannel, "..");
        assertEquals("Cancelled default service org.apache.dubbo.rpc.protocol.dubbo.support.DemoService.", result);
    }