Converting from Map<String, String> to POJO

Question

I'm creating a CSV loader class which reads records from CSV files and returns a List<T> where T is the target POJO class.

Sample CSV:

From the extracted records from CSV, it is possible to get 0 value for a Date field of a POJO class. From the sample CSV, record #2 where the value of createdDate is 0. How do I change 0 to a valid date (e.g 1970-01-01 09:00:00) first before the actual deserialization happens?

I have successfully created the process of reading a CSV file to conversion to returning List<T>.

1. Parsing: org.apache.commons.csv
2. Conversion: com.fasterxml.jackson.databind.ObjectMapper I am thinking of overriding some functions of my ObjectMapper to manipulate the values, but I have no idea how to do it.

private List<T> convertToObjectList(List<Map<String, String>> csvRecordMapList, Class<T> targetClass) {
  List<T> csvRecordObjList = new ArrayList<>();
  SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  ObjectMapper objectMapper = new ObjectMapper();
  objectMapper.setDateFormat(dateFormat);        
  objectMapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
  for(Map<String, String> recordMap : csvRecordMapList)
    csvRecordObjList.add(objectMapper.convertValue(recordMap, targetClass));

  return csvRecordObjList;
}

If I have 0 for a Date field for the target POJO class, I get the error message below (which is already expected):

Can not construct instance of java.util.Date from String value '0': not a valid representation (error: Failed to parse Date value '0': Unparseable date: "0")

Answer 1

Instead of using ObjectMapper, I used org.apache.commons.beanutils.BeanUtils and ConvertUtils. I found out that you can add a customized converter. Below are my updated source codes:

private List<T> convertToObjectList(List<Map<String, String>> csvRecordMapList, Class<T> targetClass)
    throws IllegalAccessException, InvocationTargetException, InstantiationException {
    List<T> csvRecordObjList = new ArrayList<>();
    ConvertUtils.register(getDateConverter(), Date.class);
    for (Map<String, String> recordMap : csvRecordMapList) {
        T targetClassObj = targetClass.newInstance();
        BeanUtils.populate(targetClassObj, recordMap);
        csvRecordObjList.add(targetClassObj);
    }

    return csvRecordObjList;
}

And this is my customized converter:

private static Converter getDateConverter() {
    return new Converter() {
        @SuppressWarnings({ "unchecked", "rawtypes" })
        @Override
        public Object convert(Class classType, Object value) {
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = null;
            try {
                date = value.equals("0") ? new Date(0) : sdf.parse((String) value);
            } catch (ParseException e) {
                // Do nothing
            }
            return date;
        }
    };
}