code: public static final DefaultTupleMapper newObjectDefaultTupleMapper( ) {
          final ObjectMapper mapper = new ObjectMapper();
          return new DefaultTupleMapper(new TupleMapper<String>() {
              @Override
              public String map(Tuple input) {
                  try {
                      return mapper.writeValueAsString(input.getValueByField(FIELD_SOURCE));
                  } catch (JsonProcessingException e) {
                      throw new MappingException("Error happen while processing json on object", e);
                  }
              }
          });
      }
docs: Returns a new {@link DefaultTupleMapper} that accept Object as source field value.