Dirty check when inserting POJO into DB

Example.java

//Anotation for fields need to check
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ModifiableField {

}

public abstract class PersistedObject {

	public static final long UNSET_PRIMARY_KEY = 0L;
	protected long primaryKey = UNSET_PRIMARY_KEY;

	public PersistedObject() {
	}
  
  	public long getPrimaryKey() {
		return primaryKey;
	}

	public void setPrimaryKey(long primaryKey) {
		this.primaryKey = primaryKey;
	}

	public void blankPrimaryKey() {
		primaryKey = UNSET_PRIMARY_KEY;
	}

	public boolean inDatabase() {
		return primaryKey != UNSET_PRIMARY_KEY;
	}

  
}


/**
* ModifiableObject with ModifiableField need to be checked if it's drity
*/

public class ModifiableObject extends PersistedObject {

	private boolean dirty = false;

	private Map<String, Field> modifiableFields = new HashMap<>();

	public boolean isDirty() {
		return dirty;
	}

	public void setDirty(boolean dirty) {
		this.dirty = dirty;
	}

	public ModifiableObject() {
		getModifiableFields();
	}

	protected boolean setPersistedField(String fieldName, Object newValue) {

		boolean changed = false;
		Field field = modifiableFields.get(fieldName);
		if (field == null) {
			throw new IllegalArgumentException("Field " + fieldName + " is not persisted for class" + getClass().getCanonicalName());
		}

		try {
			Object currentValue = field.get(this);
			if (currentValue == null && newValue != null || currentValue != null && !currentValue.equals(newValue)) {
				this.dirty = true;
				changed = true;
			}
			field.set(this, newValue);

		} catch (Exception e) {
			throw new IllegalStateException("Could not modify field " + fieldName, e);
		}

		return changed;
	}

	private void getModifiableFields() {

		List<Field> allFields = new ArrayList<>();
		getAllFields(allFields, this.getClass());

		for (Field field : allFields) {
			if (field.getAnnotation(ModifiableField.class) != null) {
				field.setAccessible(true);
				modifiableFields.put(field.getName(), field);
			}
		}
	}

	private static void getAllFields(List<Field> fields, Class<?> type) {
		fields.addAll(Arrays.asList(type.getDeclaredFields()));

		if (type.getSuperclass() != null) {
			getAllFields(fields, type.getSuperclass());
		}
	}

}

//----------POJO--------------
public static class Meeting extends ModifiableObject {

		@ModifiableField
		private LocalDate meetingDate;

		@ModifiableField
		private String trackCondition;

		Getter, Setter toString...

	}
  
//-------Service------
@Service
public class CanonicalServiceImpl implements CanonicalService {

  @Autowired
	private MeetingDAO meetingDAO;

  @Override
	public void saveMeeting(Meeting meeting) {
    if (meeting == null) {
			throw new IllegalArgumentException("Must provide a non-null meeting");
		}

		if (meeting.inDatabase()) {
			if (meeting.isDirty()) {
				meetingDAO.update(meeting);
			}

		} else {
			meetingDAO.insert(meeting);
		}
  }
}

//---------DAO---------
@Repository
public class MybatisMeetingDAO implements MeetingDAO {
 
  @Override
	public Meeting insert(Meeting meeting) {

		MeetingStub stub = new MeetingStub(meeting, gson.toJson(meeting));
		mapper.insertMeeting(stub);
		meeting.setPrimaryKey(stub.getMeetingId());
		meeting.setDirty(false);

		return meeting;
	}
  
  @Override
	public Meeting update(Meeting meeting) {

		MeetingStub stub = new MeetingStub(meeting, gson.toJson(meeting));
		mapper.updateMeeting(stub);
		meeting.setDirty(false);

		return meeting;
	}
 
 }