Custom Gson Deserialization

custom_gson_deserialization

public class CarVO implements Serializable {

    @Retention(RetentionPolicy.RUNTIME)
    @Target({ElementType.FIELD})
    public @interface SkipThis {
        // Field tag only annotation
    }

    private static final long serialVersionUID = 1824858721250363381L;

    @SkipThis
    private List<SeatVO> seats;

    private String name;

    private String description;
    
    public CarVO() {}
    
    public void setSeats(List<SeatVO> seats) {
      this.seats = seats;
    }
    
    public List<SeatVO> getSeats() {
      return this.seats;
    }
    
    public void setName(String name) {
      this.name = name;
    }
    
    public String getName() {
      return this.name;
    }
    
    public void setDescription(String description) {
      this.description = description;
    }
    
    public String getDescription() {
      return this.description;
    }
}

/**
 * Custom Gson Deserializer to exclude seats that have no buckles
 *
 * @return Gson
 */
private Gson getGson() {
    GsonBuilder b = new GsonBuilder();
    b.setExclusionStrategies(new SkipThisAnnotationExclusionStrategy());
    b.registerTypeAdapter(CarVO.class, new JsonDeserializer<CarVO>() {
        @Override
        public CarVO deserialize(JsonElement json, Type arg1,
                                      JsonDeserializationContext arg2) throws JsonParseException {
            JsonObject carsJSON = json.getAsJsonObject();
            JsonArray seatsJSON = carsJSON.getAsJsonArray("seats");

            Gson g = new Gson();
            CarVO carVO = g.fromJson(json, CarVO.class);
            List<SeatVO> res = new ArrayList<SeatVO>();

            for (JsonElement elem : seatsJSON) {
                JsonArray bucklesJSON = elem.getAsJsonObject().getAsJsonArray("buckles");
                if (!bucklesJSON.isJsonNull() && bucklesJSON.size() > 0) {
                    res.add(g.fromJson(elem, SeatVO.class));
                }
            }

            carVO.setSeats(res);

            return carVO;
        }
    });

    return b.create();
}

private static class SkipThisAnnotationExclusionStrategy implements ExclusionStrategy {
    public boolean shouldSkipClass(Class<?> clazz) {
        return clazz.getAnnotation(CarVO.SkipThis.class) != null;
    }

    public boolean shouldSkipField(FieldAttributes f) {
        return f.getAnnotation(CarVO.SkipThis.class) != null;
    }
}