How do I save the state of my program?

Question

For my program I have two buttons, "Add" and "Save". When I click "Add" a button is added to the JPanel. My question is, how do I save the current state of my program with all the buttons the user added? Do I use serialization? Here is a snippet of my code:

public class saveButton
{
   //JFrame and JPanels have been declared earlier

   class ClickListener implements ActionListener
   {
       public void actionPerformed(ActionEvent e)
       {
           String str = JOptionPane.showInputDialog("Name of button");
           JButton b = new JButton(str);
           frame.add(b);
       }
   }
   ActionListener addButtonClicked = new ClickListener();
   b.addActionListener(addButtonClicked);

   class ClickListenerTwo implements ActionListener
   {
       public void actionPerformed(ActionEvent f)
       {
           //save all of the program 
       }

   } 

}

Answer 1

You can only serialize (meaning straight Java serialization) if your object and every non-transient member within the class supports serialization. This is not always possible.

However, you could define your own configuration object that contains the necessary state information and save it whenever (could be just before closing app, could be every time the state changes, it's up to you) and serialization might be a way to do it

Answer 2

It depends on how you save it. You can write the state onto a file and then recover it from there by reading it. The number of buttons and the order etc. You have to decide on the format on how you want to save it too. For example you may want to store in one line

Save,JButton,imageSrc,xpos,ypos

So when you read that line and split on ',' you know that Save is the text, JButton is the class, etc.

Hope this helps

Answer 3

I would write my own file format rather than deal with the overhead of Java's serialization. This has the benefit of being more easily readable in other languages and of slightly better performance. Furthermore, as @MadProgrammer pointed out the Serialization of Swing object is not currently supported and will not be compatible with future releases:

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.

(link)

Here is an example:

public void saveState(){
    File stateFile = new File("./stateFile");
    FileOutputStream fos = new FileOutputStream(stateFile);
    DataOutputStream dos = new DataOutputStream(fis);

    for(JButton button : jButtons){ //store the buttons in an arraylist when they are created (you could also iterate over the added components and use instanceof)
        dos.writeUTF(button.getText());
    }

    dos.writeUTF("end"); //have some sort of end marker

    dos.flush();
    dos.close();
    fos.flush();
    fos.close()
}

public void loadState(){
    File stateFile = new File("./stateFile");
    FileInputStream fis = new FileInputStream(stateFile);
    DataInputStream dis = new DataInputStream(fis);
    String name;

    while(!(name = dis.readUTF()).equals("end")){
        add(new JButton(name));
    }

    fis.close();
}