code: public static String toJson(Object obj) {
          StringWriter sw = new StringWriter();
          ObjectMapper mapper = getDefaultObjectMapper();
          try {
              JsonGenerator jg = mapper.getFactory().createGenerator(sw);
              mapper.writeValue(jg, obj);
          } catch (JsonMappingException e) {
              e.printStackTrace();
          } catch (JsonGenerationException e) {
              e.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
          return sw.toString();
      }
docs: Convert object to json. If object contains fields of type date, they will
  be converted to strings using lightblue date format.
  
  @param obj
  @return