How to get selected data in table from button click event ?

Hi guys. I want to get selected item in table.

var oModel = new sap.ui.model.odata.ODataModel("http://myserver/sap/opu/odata/sap/MySRV/");
  oTable.setModel(oModel);
  oTable.bindRows({
  path : "/GetPersonsSet"
  });

Button click event function :

readItem : function(oEvent) { 
  var oModel = new sap.ui.model.odata.ODataModel("http://myserver/sap/opu/odata/sap/MySRV/");
  var m = oTable.getModel();
        var data = m.getData();
  }

But data is null.

How to get data ?