无法序列化对象。杰克逊因JsonMappingException而崩溃

Question

这是我的代码：

  try {

        String route = mItems.get(position);
        ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        String tripString = mapper.writeValueAsString(tempTrip);
        Intent i = new Intent(activity, PSRouteDetailsActivity.class);
        i.putExtra("route", route);
        i.putExtra("trip", tripString);
        i.putExtra("address", address);
        if (null != completedTripDepartureTime) {
            i.putExtra("completedTripDepartureTime", completedTripDepartureTime);
        } else if (mustChooseDepartureTime) {
            i.putExtra("mustChooseDepartureTime", true);
        }
        if (checkout) {
            i.putExtra(PSRouteDetailsActivity.SHOULD_CHECKOUT_EXTRA_KEY, true);
        }
        activity.startActivity(i);
    } catch (Exception e) {
        Utils.appendLog("pressed on details Container" + e.getMessage(), "E", Constants.PLANNER);
    }

tempTrip是一个PSTrip对象。我创建空，然后在里面添加所需的数据。 崩溃是这样的：

com.fasterxml.jackson.databind.JsonMappingException: Attempt to invoke virtual method 'boolean java.lang.String.contentEquals(java.lang.CharSequence)' on a null object reference (through reference chain: nl.hgrams.passenger.model.trip.PSTrip["active"])

当我尝试从对象创建String时，会发生这种情况：

  ObjectMapper mapper = new ObjectMapper();
        mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
        String tripString = mapper.writeValueAsString(tempTrip);

为什么会这样？我已经设置了不包含NULL对象

这是我的PSTrip对象的外观（没有方法和getter设置器）

 @RealmClass
public class PSTrip extends RealmObject implements Serializable {

private static String TAG = PSTrip.class.getName();

private int update_interval;
private String travel_mode;
@PrimaryKey
private String id;
private String icon;
private String status;
private String notes;
private Destination destination;
private Destination origin;
private Long departure_time, arrival_time;
private Route route;
private Owner_data owner;
private String vehicle;
private Flight flight;
private double last_updated;
private MileageExpenses mileage_expenses;
private RealmList<TripStep> steps;
private RealmList<TripStop> pendingTripStops = new RealmList<>();
private RealmList<Tag> tags = new RealmList<>();
private RealmList<RealmInt> usedVehicles = new RealmList<>();
private Planned_Route planned_route;
private Group group;
private Stats stats;
private String icon_small;
private Integer revised;
private double avgspeed;
private float delay;
private boolean deleted = false;

public final static String STATUS_ACTIVE = "active";
public final static String STATUS_COMPLETED = "completed";
public static boolean isCheckingOut = false, isAddingPitstop = false, isUpdatingLocation = false, isAborting = false;
public static Float kPSMinRoundTripLength = 250f, kPSInterPitStopDistance = 150f, kPSMinDistanceCheckout = 100f;
public static Long kPSLongTimeForCheckout = 900l, kPSShortTimeForCheckout = 300l;
public static final Double kPSminTripLength = 100d;
public static final int kPSFrequentCheckoutPlace = 5;

public static double minDistanceToDestination = 999999999;
}