How to pass java var to bpmn?

I need to get data from one rest api to another using camunda build a orchestrator with all json format.
I get input variable value from postman, then try to pass that value to another rest api via the Connector in bpmn.
I keep getting err: ENGINE-16004 Exception while closing command context: org.camunda.spin.impl.json.jackson.JacksonJsonNode cannot be cast to java.lang.String.
in java code I have a listener implements ExecutionListener:
@Override
public void notify(DelegateExecution execution) throws Exception {
Object employeeDataObj = (String)execution.getVariable(“employeeData”);
Gson gson = new GsonBuilder().create();
Object employeeDataObjGson = gson.toJson(employeeDataObj);
execution.setVariable(employeeDataGson, employeeDataObjGson);
System.out.println(“execution.getVariable(employeeDataGson): |”+execution.getVariable(“employeeDataGson”)+"|");
in log I see:
execution.getVariable(employeeDataGson): |"{“PersonNumber”:“955160008184099”,“FirstName”: “Jocob”,“LastName”: “George”,“EffectiveStartDate”: “2016-04-13”,";BusinessUnitId":300100083931674,“LegalEntityId”:40010,“assignments”:[{ “ActionCode”:“HIRE”,“AssignmentName”: “Jocob_Assignment_1",“BusinessUnitId”:202,“AssignmentStatus”:“ACTIVE”,“AssignmentId”: 300100083931690,“EffectiveStartDate”:“2016-04-13”,“PrimaryAssignmentFlag”: true}]}”|

in bpmn I use payload as javascript. in Script value I put this way:
S(execution.getVariable(“employeeDataGson”), ‘application/json’);

can anyone help me here?