public class NacosNamingService implements NamingService {
    private static final String DEFAULT_PORT = "8080";
    private static final long DEFAULT_HEART_BEAT_INTERVAL = TimeUnit.SECONDS.toMillis(5);

    /**
     * Each Naming instance should have different namespace.
     */
    private String namespace;

    private String endpoint;

    private String serverList;

    private String cacheDir;

    private String logName;

    private HostReactor hostReactor;

    private BeatReactor beatReactor;

    private EventDispatcher eventDispatcher;

    private NamingProxy serverProxy;

    //......

    @Override
    public ListView<String> getServicesOfServer(int pageNo, int pageSize) throws NacosException {
        return serverProxy.getServiceList(pageNo, pageSize, Constants.DEFAULT_GROUP);
    }

    @Override
    public ListView<String> getServicesOfServer(int pageNo, int pageSize, String groupName) throws NacosException {
        return getServicesOfServer(pageNo, pageSize, groupName, null);
    }

    @Override
    public ListView<String> getServicesOfServer(int pageNo, int pageSize, AbstractSelector selector)
        throws NacosException {
        return getServicesOfServer(pageNo, pageSize, Constants.DEFAULT_GROUP, selector);
    }

    @Override
    public ListView<String> getServicesOfServer(int pageNo, int pageSize, String groupName, AbstractSelector selector) throws NacosException {
        return serverProxy.getServiceList(pageNo, pageSize, groupName, selector);
    }

    //......
}

public class NamingProxy {

    private static final int DEFAULT_SERVER_PORT = 8848;

    private int serverPort = DEFAULT_SERVER_PORT;

    private String namespaceId;

    private String endpoint;

    private String nacosDomain;

    private List<String> serverList;

    private List<String> serversFromEndpoint = new ArrayList<String>();

    private long lastSrvRefTime = 0L;

    private long vipSrvRefInterMillis = TimeUnit.SECONDS.toMillis(30);

    private Properties properties;

    //......

    public ListView<String> getServiceList(int pageNo, int pageSize, String groupName) throws NacosException {
        return getServiceList(pageNo, pageSize, groupName, null);
    }

    public ListView<String> getServiceList(int pageNo, int pageSize, String groupName, AbstractSelector selector) throws NacosException {

        Map<String, String> params = new HashMap<String, String>(4);
        params.put("pageNo", String.valueOf(pageNo));
        params.put("pageSize", String.valueOf(pageSize));
        params.put(CommonParams.NAMESPACE_ID, namespaceId);
        params.put(CommonParams.GROUP_NAME, groupName);

        if (selector != null) {
            switch (SelectorType.valueOf(selector.getType())) {
                case none:
                    break;
                case label:
                    ExpressionSelector expressionSelector = (ExpressionSelector) selector;
                    params.put("selector", JSON.toJSONString(expressionSelector));
                    break;
                default:
                    break;
            }
        }

        String result = reqAPI(UtilAndComs.NACOS_URL_BASE + "/service/list", params);

        JSONObject json = JSON.parseObject(result);
        ListView<String> listView = new ListView<String>();
        listView.setCount(json.getInteger("count"));
        listView.setData(JSON.parseObject(json.getString("doms"), new TypeReference<List<String>>() {
        }));

        return listView;
    }

    //......
}

public class ListView<T> {

    private List<T> data;
    private int count;

    public List<T> getData() {
        return data;
    }

    public void setData(List<T> data) {
        this.data = data;
    }

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    @Override
    public String toString() {
        return JSON.toJSONString(this);
    }
}