返回JSONObject后，“ HttpMessageNotWritableException：无法写入内容：”引发此异常吗？

Question

// 控制器

@RequestMapping(value ="/getCount", method = RequestMethod.GET,produces=MediaType.APPLICATION_JSON_VALUE)
public  ResponseEntity <?> getCount() {

    Long activeCount = cameraMasterServiceImpl.getCount();
    return new ResponseEntity (activeCount, HttpStatus.OK);

}

// dao

public JSONObject getCount() {
    // TODO Auto-generated method stub
    Session session = null;
    Transaction transaction = null;
    Long countActive = null;
    Long countInactive = null;
    Long allCameraCount = null;

    JSONObject jsonobject = new JSONObject();
    try {
        session = sessionfactory.openSession();
        transaction = session.beginTransaction();

        //counting all active
        Criteria criteriaA = session.createCriteria(CameraMaster.class);
        criteriaA.add(Restrictions.eq("cameraStatus", "Active"));
        criteriaA.setProjection(Projections.rowCount());                        
        List<?> dataA = criteriaA.list();
        if (dataA!=null) {
            countActive = (Long) dataA.get(0);
        }

        //counting all inactive
        Criteria criteriaI = session.createCriteria(CameraMaster.class);
        criteriaI.add(Restrictions.eq("cameraStatus", "Inactive"));
        criteriaI.setProjection(Projections.rowCount());                        
        List<?> dataI = criteriaI.list();
        if (dataI!=null) {
            countInactive = (Long) dataI.get(0);
        }

        jsonobject.put("countActive",countActive);
        jsonobject.put("countInactive",countInactive);
        System.out.println(jsonobject);

        transaction.commit();
        session.close();
    } catch (Exception ex) {
        transaction.rollback();
        session.close();
        ex.printStackTrace();
    }
    return jsonobject;

}

///同时检索数据（jsonobject）“ http://localhost:8080/sample/count/getCount” // 引发以下异常

  

org.springframework.http.converter.HttpMessageNotWritableException：无法写入内容：没有为类找到序列化程序   org.json.JSONObject，没有发现要创建的属性   BeanSerializer（为避免异常，请禁用   SerializationFeature.FAIL_ON_EMPTY_BEANS））;嵌套异常为   com.fasterxml.jackson.databind.JsonMappingException：没有序列化程序   为类org.json.JSONObject找到，没有发现任何属性   创建BeanSerializer（为避免异常，请禁用   SerializationFeature.FAIL_ON_EMPTY_BEANS））