jackson json date format convert

Question

Please help to change date format.

**Source** json file

**Target** Employee Object

I need support for converting file json date to Object. from file

{
 "dateOfBirth": {
    "year": 1980,
    "month": "MAY",
    "monthValue": 5,
    "dayOfMonth": 4,
    "dayOfYear": 124,
    "dayOfWeek": "WEDNESDAY",
    "chronology": {
      "calendarType": "iso8601",
      "id": "ISO"
    },
    "era": "CE",
    "leapYear": false
  }
}

to Object

{"dateOfBirth": "1980-05-04"}

Object

public class Employee {   
    private LocalDate dateOfBirth;
    //setter
    //getter
}

Library "com.fasterxml.jackson.datatype:jackson-datatype-jsr310"

Date: java.time.LocalDate

My goal is to read json data from file and map it to object.

Answer 1

You can use custom deserializer.

public class EmployeeBirthDateDeserializer extends StdDeserializer<LocalDate> {

  public EmployeeBirthDateDeserializer() {
    super(LocalDate.class);
  }

  @Override
  public LocalDate deserialize(JsonParser parser, DeserializationContext context) throws IOException {
    JsonNode root = parser.getCodec().readTree(parser);
    return LocalDate.of(root.get("year").asInt(), root.get("monthValue").asInt(), root.get("dayOfMonth").asInt());
  }
}

Then apply it only to dateOfBirth field in Employee using @JsonDeserialize :

public class Employee {

  @JsonDeserialize(using = EmployeeBirthDateDeserializer.class)
  private LocalDate dateOfBirth;

  //getters and setter
}

Test:

public class Temp {

  public static void main(String[] args) throws IOException {
    ObjectMapper mapper = new ObjectMapper();
    Employee employee = mapper.readValue(ClassLoader.getSystemResourceAsStream("strange-date.json"), Employee.class);
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    System.out.println(formatter.format(employee.getDateOfBirth()));
  }
}

Prints: 1980-05-04 .