如何为我的项目实现 Serializable 以具有持久性？

Question

我的主要方法：

public class ToDoList extends Application{

public static void main(String[] args) {
    launch(args);
}

public void start(Stage primaryStage) throws Exception {

    Pane pane = FXMLLoader.load(getClass().getResource("ToDoList.fxml"));

    Scene scene = new Scene(pane);
    scene.getStylesheets().add(getClass().getResource("ToDoListStyle.css").toExternalForm());
    primaryStage.setScene(scene);
    primaryStage.setTitle("Plan yourself");
    primaryStage.show();
}

}

然后是控制器的一部分：

    ObservableList<EventsBean> dataList = FXCollections.observableArrayList();

@Override
public void initialize(URL location, ResourceBundle resources) {
    System.out.println("The pane loaded");

    List<String> myList;
    try {
        myList = Files.lines(Paths.get("src/com/todolist/EventsList.txt")).collect(Collectors.toList());
        eventsSelector.setItems(FXCollections.observableArrayList(myList));
    } catch (IOException e) {
        System.out.println("Don t find file");
    }

    removeCol.setCellFactory(CheckBoxTableCell.forTableColumn(removeCol));
    eventCol.setCellValueFactory(new PropertyValueFactory<EventsBean, String>("event"));
    dateCol.setCellValueFactory(new PropertyValueFactory<EventsBean, LocalDate>("date"));
    doneCol.setCellValueFactory(new PropertyValueFactory<EventsBean, String>("done"));
    doneCol.setCellFactory(TextFieldTableCell.<EventsBean>forTableColumn());
    doneCol.setOnEditCommit((CellEditEvent<EventsBean, String> t) -> {
        ((EventsBean) t.getTableView().getItems().get(t.getTablePosition().getRow()))
                .setDone(t.getNewValue());
    });
    observationCol.setCellValueFactory(new PropertyValueFactory<EventsBean, String>("observation"));
    removeCol.setCellValueFactory(cellData -> cellData.getValue().selectedProperty());
    observationCol.setCellFactory(TextFieldTableCell.<EventsBean>forTableColumn());
    observationCol.setOnEditCommit((CellEditEvent<EventsBean, String> t) -> {
        ((EventsBean) t.getTableView().getItems().get(t.getTablePosition().getRow()))
                .setObservation(t.getNewValue());
    });
    observationCol.setSortable(false);

    eventsTable.setItems(dataList);
    eventsTable.setEditable(true);

    bttnAddEvent.setOnAction((ActionEvent e) -> {
        try {
            text = eventsSelector.getValue().toString();
            dataList.add(new EventsBean(text, isoDate, "",  "", false));
        } catch (Exception e1) {
            System.out.println("Nothing selected");
        }
    });

    bttnRemove.setOnAction((ActionEvent e) -> {
        ObservableList<EventsBean> dataListToRemove = FXCollections.observableArrayList();
        for (EventsBean bean : dataList) {
            if (bean.getSelected()) {
                dataListToRemove.add(bean);
            }
        }
        dataList.removeAll(dataListToRemove);

        // Below code it is for delete a focused row
        // EventsBean selectedItem = eventsTable.getSelectionModel().getSelectedItem();
        // eventsTable.getItems().remove(selectedItem);
    });

}

然后是EventsBean：

public class EventsBean {


private SimpleStringProperty event;
private SimpleObjectProperty<LocalDate> date;
private SimpleStringProperty done;
private SimpleStringProperty observation;
private SimpleBooleanProperty selected;

public EventsBean(String event, LocalDate date, String done, String observation, boolean selected) {
    this.event = new SimpleStringProperty(event);
    this.date = new SimpleObjectProperty<LocalDate>(date);
    this.done = new SimpleStringProperty(done);
    this.observation = new SimpleStringProperty(observation);
    this.selected = new SimpleBooleanProperty(selected);
}
// Getters and Setters ...

我想序列化表中的数据。我认为可序列化的对象是 ObservableList 中的 dataList。我的问题是在哪里实现 Serializable 接口？这是我持久性的最佳解决方案吗？

提前谢谢你！

Answer 1

您应该首先问自己是否真的想在这里使用对象序列化。使用不同的持久性方法可能会更好：例如使用 JSON 封送库，例如 GSON。大多数此类库仅使用对象的 get 和 set 方法来查找数据，因此很可能与您的 EventsBean 类一起使用，几乎不需要额外的代码。

如果您确实想使用 Java 对象序列化，则需要将 EventsBean 类设为 Serializable。通常这很简单，但您会遇到的问题是 JavaFX 属性类没有实现 Serializable，所以天真地让 EventsBean 实现 Serializable 并尝试序列化它的实例会产生运行时异常。您需要使用自定义序列化来执行此操作。

首先，将 JavaFX 属性设为transient，这样默认的序列化机制不会尝试对其进行序列化，然后定义自定义的readObject 和writeObject 方法来定义对象应如何序列化：

public class EventsBean implements Serializable {


    private transient SimpleStringProperty event;
    private transient SimpleObjectProperty<LocalDate> date;
    private transient SimpleStringProperty done;
    private transient SimpleStringProperty observation;
    private transient SimpleBooleanProperty selected;

    // constructors...

    // example get/set/property methods:
    public StringProperty eventProperty() {
        return event ;
    }

    public final String getEvent() {
        return eventProperty().get();
    }

    public final void setEvent(String event) {
        eventProperty().set(event);
    }

    // etc. for other properties...


    // custom serialization:
    private void writeObject(ObjectOutputStream s) throws IOException {
        s.defaultWriteObject();
        s.writeObject(getEvent()); // write event as a plain String
        s.writeObject(getDate()); 
        s.writeObject(getDone());
        s.writeObject(getObservation());
        s.writeBoolean(isSelected());
    }

    // custom deserialization:
    private void readObject(ObjectInputStream s) throws IOException {
        s.defaultReadObject();
        this.event = new SimpleStringProperty((String)s.readObject());
        this.data = new SimpleObjectProperty<>((LocalDate)s.readObject());
        this.done = new SimpleStringProperty((String)s.readObject());
        this.observation = new SimpleStringProperty((String)s.readObject());
        this.selected = new SimpleBooleanProperty(s.readBoolean());
    }
}

最后，您还需要注意ObservableList 实现通常是不可序列化的，因此您需要序列化一个“常规”列表才能序列化数据，即：

ObjectOutputStream s = ... ;
s.writeObject(new ArrayList<EventsBean>(dataList));

然后再读一遍：

ObjectInputStream s = ... ;
dataList.setAll((List<EventsBean>)s.readObject());