How to serialize ObservableList

Question

I am working on a javaFx project where we have to use ObservableList to add Listners. ObservableList includes Model of persons. But I want to store the whole ObservableList Object in a file through serialization. But it gives me an Exception. I also implimented Serialization on the object Model but no luck. Is there any method to serialize ObservableList?

EmployeeModel

package com.company.Model;

import javax.persistence.*;
import java.io.Serializable;

/**
 * Created by Sunny on 1/8/2016.
 */
@Entity
@Table(name = "Employee", schema = "", catalog = "PUBLIC")
public class EmployeeEntity implements Serializable {
    private String empId;
    private String empAddress;
    private String empNumber;
    private String empFirstName;
    private String empLastName;

    public EmployeeEntity(String empId, String empAddress, String empNumber, String empFirstName, String empLastName) {
        this.empId = empId;
        this.empAddress = empAddress;
        this.empNumber = empNumber;
        this.empFirstName = empFirstName;
        this.empLastName = empLastName;
    }

    public EmployeeEntity() {

    }

    @Id
    @Column(name = "emp_ID")
    public String getEmpId() {
        return empId;
    }

    public void setEmpId(String empId) {
        this.empId = empId;
    }

    @Basic
    @Column(name = "emp_address")
    public String getEmpAddress() {
        return empAddress;
    }

    public void setEmpAddress(String empAddress) {
        this.empAddress = empAddress;
    }

    @Basic
    @Column(name = "emp_number")
    public String getEmpNumber() {
        return empNumber;
    }

    public void setEmpNumber(String empNumber) {
        this.empNumber = empNumber;
    }

    @Basic
    @Column(name = "emp_firstName")
    public String getEmpFirstName() {
        return empFirstName;
    }

    public void setEmpFirstName(String empFirstName) {
        this.empFirstName = empFirstName;
    }

    @Basic
    @Column(name = "emp_lastName")
    public String getEmpLastName() {
        return empLastName;
    }

    public void setEmpLastName(String empLastName) {
        this.empLastName = empLastName;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        EmployeeEntity that = (EmployeeEntity) o;

        if (empId != null ? !empId.equals(that.empId) : that.empId != null) return false;
        if (empAddress != null ? !empAddress.equals(that.empAddress) : that.empAddress != null) return false;
        if (empNumber != null ? !empNumber.equals(that.empNumber) : that.empNumber != null) return false;
        if (empFirstName != null ? !empFirstName.equals(that.empFirstName) : that.empFirstName != null) return false;
        if (empLastName != null ? !empLastName.equals(that.empLastName) : that.empLastName != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = empId != null ? empId.hashCode() : 0;
        result = 31 * result + (empAddress != null ? empAddress.hashCode() : 0);
        result = 31 * result + (empNumber != null ? empNumber.hashCode() : 0);
        result = 31 * result + (empFirstName != null ? empFirstName.hashCode() : 0);
        result = 31 * result + (empLastName != null ? empLastName.hashCode() : 0);
        return result;
    }
}

Serialization

 public void write(ObservableList<EmployeeEntity> personObservalble) {
        try {
            // write object to file
            FileOutputStream fos = new FileOutputStream("Objectsavefile.ser");
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(personsObservable);
            oos.close();


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

Exception

java.io.NotSerializableException: com.sun.javafx.collections.ObservableListWrapper
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
    at FileWriter.write(FileWriter.java:14)
    at Main.main(Main.java:12)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

Process finished with exit code 0

Northern

"I also implimented Serilization on object Model but no luck" Do you mean that you added implements Serializable to that class? Do you know that doesn't actually guarantee that instances can be serialized? – Centigram

Actually im new to programming. so my concepts are weak about serilization. Now i understands. serilization not always actually works on instences – Northern

Could you actually try the code I posted in the answer and see if it works? – Kinser

Answer 1

ObservableList implementations are not Serializable (Essentially there's no sensible way to define the behavior for serializing the listeners, and not serializing the listeners at all is just the same as serializing a non-observable list with the same data, which I think is what you want to do here.) Assuming your Person class is Serializable (and that instances can actually be serialized), you can do:

 public void write(ObservableList<EmployeeEntity> personObservalble) {
    try {
        // write object to file
        FileOutputStream fos = new FileOutputStream("Objectsavefile.ser");
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(new ArrayList<EmployeeEntity>(personsObservable));
        oos.close();


    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

To read it back in, you would do:

ObjectInputStream ois = ... ;
List<EmployeeEntity> list = (List<EmployeeEntity>) ois.readObject();
personsObservable = FXCollections.observableList(list);

Here is a complete test. I ran this and it worked (I removed the persistence annotations, as I didn't have javax.persistence on the classpath in my test environment, but that should make no difference).

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;

public class SerializeObservableListTest {

    public static void main(String[] args) throws IOException {
        EmployeeEntity bill = new EmployeeEntity("1000", "Seattle, WA", "1000", "Bill", "Gates");
        EmployeeEntity tim = new EmployeeEntity("2000", "Mobile, AL", "2000", "Tim", "Cook");

        ObservableList<EmployeeEntity> staff = FXCollections.observableArrayList(bill, tim);

        Path temp = Files.createTempFile("employees", "ser");
        write(staff, temp);

        ObservableList<EmployeeEntity> listFromFile = read(temp);
        System.out.println("Lists equal? "+listFromFile.equals(staff));
    }

    private static void write(ObservableList<EmployeeEntity> employees, Path file) {
        try {

            // write object to file
            OutputStream fos = Files.newOutputStream(file);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(new ArrayList<EmployeeEntity>(employees));
            oos.close();


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static ObservableList<EmployeeEntity> read(Path file) {
        try {
            InputStream in = Files.newInputStream(file);
            ObjectInputStream ois = new ObjectInputStream(in);
            List<EmployeeEntity> list = (List<EmployeeEntity>) ois.readObject() ;

            return FXCollections.observableList(list);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return FXCollections.emptyObservableList();
    }
}

Kinser

But youn can see i have implements seriilization on EmployeeModel. still i cant do serilization. – Northern

It ran just fine for me. See updated answer. Post the stack trace in your question if it's really not working using this technique. – Kinser

But the exception you posted doesn't use the code I wrote for you. – Kinser

That exception says you are still trying to serialize the observable list. Please try it like I suggested. – Kinser

Same Exception presist on the main code. Actually i have converted ObservalbleList to ArrayList for serilization in my code... – Northern

Seriously, it is impossible to get that exception using the code I posted. Just read the error message: it says you are serializing an observable list. Line 14 of FileWriter has oos.writeObject(new ArrayList<EmployeeEntity>(personsObservable));? – Kinser

thank you for the correction. I have understand that ObservableList cannot be serilize. We have to convert it to arrayList then serilize it. After that we can again covert it back to ObservableList. – Northern

@James_D, if a class contains an ObservableList and it implements serializable, when exporting an object of this class to a file it does not seem to raise any exception. Why and what is the state of the ObservableList content? – Satiny