Issue on QueryText when using RIDC GET_SEARCH_RESULTS service

I am using http protocal to connect to local VM UCM in 12c.

and when perform GET_SEARCH_RESULTS, if QueryText is empty, I can get results back.

But if I put QueryText, got the following error:

oracle.stellent.ridc.protocol.ServiceException: Unable to retrieve search results. The query text is invalid.

Here is my sample code:

try {

    //connectionURL= "http://localhost:7777/cs/idcplg";

    IdcClientManager manager = new IdcClientManager();                

    IdcClient idcClient = manager.createClient(connectionURL);          

    idcClient.getConfig ().setProperty ("http.library", "oracle");          

    IdcContext userContext = new IdcContext(user,pass);

    

    idcClient.getConfig().setSocketTimeout(60000);

    DataBinder binder = idcClient.createBinder ();

    binder.putLocal("IdcService", "GET_SEARCH_RESULTS");          

    //binder.putLocal("QueryText", ""); -- this works fine and can get results back.