Java で Jackson ライブラリを使用して日付をフォーマットするにはどうすればよいですか?

public ObjectMapper setDateFormat(DateFormat dateFormat)

import java.io.*;
import java.text.*;
import java.util.*;
import com.fasterxml.jackson.databind.*;

public class JacksonDateformatTest {
   final static ObjectMapper mapper = new ObjectMapper();
   public static void main(String[] args) throws Exception {
      JacksonDateformatTest jacksonDateformat = new JacksonDateformatTest();
      DateFormat df = new SimpleDateFormat("yyyy-MM-dd");
      mapper.setDateFormat(df);
      jacksonDateformat.dateformat();
}
   public void dateformat() throws Exception {
      String json = "{\"birthDate\":\"1980-12-08\"}";
      Reader reader = new StringReader(json);
      Employee emp = mapper.readValue(reader, Employee.class);
      System.out.println(emp);
   }
}

// Employee class
class Employee implements Serializable {
   private Date birthDate;
   public Date getBirthDate() {
      return birthDate;
   }
   public void setBirthDate(Date birthDate) {
      this.birthDate = birthDate;
   }
   @Override
   public String toString() {
      return "Employee [birthDate=" + birthDate + "]";
   }
}

Employee [birthDate=Mon Dec 08 00:00:00 IST 1980]