java.lang.UnsupportedOperationException JavaFX ArrayList<String> to ObservableList<StringProperty>

Question

I'm having trouble with Java FX i'm currently trying to serialize an object and for that i'm creating a class that convert object from javaFX to serializable object. But when i'm trying to load back object i get

  Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.control.MenuItem.fire(MenuItem.java:462)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$343(ContextMenuContent.java:1358)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.Trampoline.invoke(Unknown Source)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1771)
    ... 43 more


 Caused by: java.lang.UnsupportedOperationException
    at java.util.AbstractList.add(Unknown Source)
    at java.util.AbstractList.add(Unknown Source)
    at view.OverviewInterroController.handleLoad(OverviewInterroController.java:172)
    ... 53 more

The code that cause it :

package model;

import java.io.Serializable;
import java.util.ArrayList;

import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;

public class QuestionSerializable implements Serializable {

    private final String question;
    private final String typeReponse;
    private final int nbLignesReponse;
    private final ArrayList<String> reponseData = new ArrayList<String>();


    public QuestionSerializable(QuestionModel model)
    {
        this.question = model.getQuestion().getValue();
        this.typeReponse = model.getTypeReponse().getValue();
        this.nbLignesReponse = model.getNbLignesReponse().getValue();
        for(StringProperty val : model.getReponseData().getValue())
        {
            reponseData.add(val.getValue());
        }
    }

    public QuestionModel convert()
    {
        QuestionModel qm = new QuestionModel(question);
        qm.getNbLignesReponse().setValue(this.nbLignesReponse);
        qm.getTypeReponse().setValue(typeReponse);
        ObjectProperty<ObservableList<StringProperty>> reponseData2 =qm.getReponseData();
        for(String val : reponseData)
        {
            reponseData2.getValue().add(new SimpleStringProperty(val));
        }
        return qm;
    }
}

And specially :

ObjectProperty<ObservableList<StringProperty>> reponseData2 =qm.getReponseData();
for(String val : reponseData)
{
    reponseData2.getValue().add(new SimpleStringProperty(val));
}

And the OverviewController

package view;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;

import com.itextpdf.text.xml.simpleparser.handler.NeverNewLineHandler;

import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Label;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.FileChooser;
import model.QuestionModel;
import model.QuestionSerializable;
import principale.Main;

public class OverviewInterroController {

    @FXML
    private TableView<QuestionModel> questionTable;
    @FXML
    private TableColumn<QuestionModel,String> questionColumn; 
    @FXML
    private Label questionLabel;
    @FXML
    private Label typeLabel;
    @FXML
    private Label nbLigneLabel;
    @FXML
    private TableView<StringProperty> reponseTable;
    @FXML
    private TableColumn<ObservableList<StringProperty>,String> reponseColumn;

    // Reference to the main application.
    private Main mainApp;

    @FXML
    private void initialize()
    {
        questionColumn.setCellValueFactory(cellData -> cellData.getValue().getQuestion());
        showQuestionDetails(null);

        questionTable.getSelectionModel().selectedItemProperty().addListener(
                (observable,oldvalue,newValue)-> showQuestionDetails(newValue));
    }

    public void showReponseTable(QuestionModel question)
    {
        if(question.getTypeReponse().getValue().equals("Cocher"))
        {
            reponseTable.setItems(question.getReponseData().getValue());
            reponseColumn.setCellValueFactory(new PropertyValueFactory<>("value"));
            reponseTable.setVisible(true);
        }else
        {
            this.reponseTable.setVisible(false);
        }
    }

    public void setMainApp(Main mainApp) {
        this.mainApp = mainApp;
        questionTable.setItems(mainApp.getQuestionData());
    }


    public void handleImprimer()
    {
        mainApp.showImprimerDialog();
    }

    public void handleClose()
    {
        System.exit(0);
    }


    public void showQuestionDetails(QuestionModel question)
    {
        if(question != null)
        {
            questionLabel.setText(question.getQuestion().getValue());
            typeLabel.setText(question.getTypeReponse().getValue());
            nbLigneLabel.setText(Integer.toString(question.getNbLignesReponse().getValue()));
            reponseTable.setItems(FXCollections.emptyObservableList());
            showReponseTable(question);
        }else
        {
            questionLabel.setText("");
            typeLabel.setText("");
            nbLigneLabel.setText("0");
            reponseTable.setVisible(false);
        }
    }



    public void handleDelete()
    {
        int selectedIndex = questionTable.getSelectionModel().getSelectedIndex();
        if(selectedIndex>=0)
        {
        questionTable.getItems().remove(selectedIndex);
        }else
        {
            Alert alert = new Alert(AlertType.ERROR);
            alert.initOwner(mainApp.getPrimaryStage());
            alert.setTitle("Aucune question séléctionnée !");
            alert.setContentText("Veuillez séléctionner une question valide !");

            alert.showAndWait();
        }
    }

    public void handleSave() throws IOException
    {
        FileChooser fileChooser = new FileChooser();

        //Set extension filter
        FileChooser.ExtensionFilter extFilter = new FileChooser.ExtensionFilter("CTRL Files (*.ctrl)", "*.ctrl");
        fileChooser.getExtensionFilters().add(extFilter);

        //Show save file dialog
        File file = fileChooser.showSaveDialog(this.mainApp.getPrimaryStage());

        if(file != null){
            FileOutputStream fout = new FileOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(fout);
            ArrayList<QuestionSerializable> qs = new ArrayList<QuestionSerializable>();
            for(QuestionModel qm : this.mainApp.getQuestionData())
            {
                qs.add( new QuestionSerializable(qm));
            }

            oos.writeObject(new ArrayList<QuestionModel>(this.mainApp.getQuestionData()));
            oos.close();
            fout.close();
        }
    }

    @SuppressWarnings("unchecked")
    public void handleLoad() throws Exception
    {
        FileChooser fileChooser = new FileChooser();

        //Set extension filter
        FileChooser.ExtensionFilter extFilter = new FileChooser.ExtensionFilter("CTRL Files (*.ctrl)", "*.ctrl");
        fileChooser.getExtensionFilters().add(extFilter);

        //Show save file dialog
        File file = fileChooser.showSaveDialog(this.mainApp.getPrimaryStage());

        if(file != null){
            FileInputStream fout = new FileInputStream(file);
            ObjectInputStream oos = new ObjectInputStream(fout);
            ArrayList<QuestionSerializable> qm = (ArrayList<QuestionSerializable>) oos.readObject();
            ObservableList<QuestionModel> qo = FXCollections.emptyObservableList();
            for(QuestionSerializable q : qm)
            {
                qo.add(q.convert());
            }
            this.mainApp.setQuestionData(qo);
            this.questionTable.refresh();
            this.showQuestionDetails(null);
            oos.close();
            fout.close();
        }
    }

    public void handleNew()
    {
        QuestionModel tempQuestion = new QuestionModel("");
        tempQuestion.getReponseData().getValue().add(new SimpleStringProperty(""));
        boolean okClicked = mainApp.showPersonEditDialog(tempQuestion);
        if (okClicked) {
            mainApp.getQuestionData().add(tempQuestion);
        }

    }

    public void handleEdit()
    {
        QuestionModel selectedQuestion = questionTable.getSelectionModel().getSelectedItem();
        if(selectedQuestion!=null)
        {
            boolean okClicked = mainApp.showPersonEditDialog(selectedQuestion);
            if (okClicked) {
                showQuestionDetails(selectedQuestion);
                this.reponseTable.refresh();
            }
        }else
        {
            Alert alert = new Alert(AlertType.ERROR);
            alert.initOwner(mainApp.getPrimaryStage());
            alert.setTitle("Aucune question séléctionnée !");
            alert.setContentText("Veuillez séléctionner une question valide !");

            alert.showAndWait();
        }
    }

}

And line 172 is :

ObservableList<QuestionModel> qo = FXCollections.emptyObservableList();
for(QuestionSerializable q : qm)
{
    qo.add(q.convert());
}

QuestionModelClass :

package model;

import java.io.Serializable;

import javafx.beans.property.IntegerProperty;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;

public class QuestionModel{

    private final StringProperty question;
    private final StringProperty typeReponse = new SimpleStringProperty("Remplir Ligne");
    private final IntegerProperty nbLignesReponse = new SimpleIntegerProperty(1);
    private ObjectProperty<ObservableList<StringProperty>> reponseData = new SimpleObjectProperty<ObservableList<StringProperty>>(FXCollections.observableArrayList());



    /**
     * @return the reponseData
     */
    public ObjectProperty<ObservableList<StringProperty>> getReponseData() {
        return reponseData;
    }

    public void setReponseData(ObjectProperty<ObservableList<StringProperty>> reponseData)
    {
        this.reponseData = reponseData;
    }

    public QuestionModel(String question)
    {
        this.question = new SimpleStringProperty(question);
    }

    /**
     * @return the nbLignesReponse
     */
    public IntegerProperty getNbLignesReponse() {
        return nbLignesReponse;
    }

    /**
     * @return the question
     */
    public StringProperty getQuestion() {
        return question;
    }

    /**
     * @return the typeReponse
     */
    public StringProperty getTypeReponse() {
        return typeReponse;
    }
}

Answer 1

FXCollections.emptyObservableList() returns a unmodifiable empty ObservableList, which is why you get the UnsupportedOperationException when you call add.

Use FXCollections.observableArrayList() to create the list instead:

ObservableList<QuestionModel> qo = FXCollections.observableArrayList();

This creates a list that can be modified. This list is initially empty.

Answer 2

Apparently the reponseData and qm.getReponseData().getValue() should have a type of ObjectProperty<List<StringProperty>>.

The FXCollections documentation specifies that the method

FXCollections.emptyObservableList()

will return an "empty unmodifiable observable list".

Therefore, the loop

for(QuestionSerializable q : qm)
{
    qo.add(q.convert());
}

will throw an UnsupportedOperationException, since the qo object is created by calling the aforementioned method.

To get a modifiable empty list, the method

FXCollections.observableArrayList()

should be called, as per the above documentation and fabian's earlier answer.