Java FileStream-ObjectOutputStream ObjectInputStream

Question

I am creating a little GUI for a "movie manager" with Java and Swing.

I have a class MovieTableModel that extends AbstractTableModel and has the data for the rows of the table in an Object[][]data. A second class MovieUI manages the JFrame and well, the GUI in general. The last class MovieManager is actually just a main function to create an instance of movieui and make it visible.

Now my problem is that by now, data is "saved" in my code. I want it to be able to be loaded and saved. If there is no save-file, one should be created and I should be able to add or delete rows of it (the actionlisteners are already set up, I just need a way to handle the file).

So the GUI looks like this: MovieManager

This is kinda what I tried:

        File tabledata = new File("tabledata.class");
    if (!tabledata.exists()) {
        try {
            tabledata.createNewFile();
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }
    }
    tabledata.



    FileInputStream in = new FileInputStream("tabledata.class");
    ObjectInputStream input = new ObjectInputStream(in);
    Object data = input.readObject();
    System.out.print(data);

Both didn't work - I think I do understand how this works in general, but I don't know how to make it to the data in my table, especially as it is saved as an Object[][] but the file is an Object. And if that works out - how can I add or delete single rows?

Thanks for your help in advance! :)

Answer 1

If you serialize you tablemodel or the object that backs your tablemodel, then you can read it later and restore it to the JTable.

When you read the object again from the ObjectInputStream, I think you are missing the cast to the right type you are saving:

FileInputStream in = new FileInputStream("tabledata.class");
ObjectInputStream input = new ObjectInputStream(in);
Object[][] data = (Object[][])input.readObject();

Answer 2

After you create new file you need to write the data using ObjectOutputStream and then read it with ObjectInputStream .

Object[][] data;
//save
File tabledata = new File("tabledata.dat"); //I wouldn't use class extension (class is for compiled Java)
//creation of file omitted
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(tabledata));
out.writeObject(data);
out.close();

//load
ObjectInputStream  in = new ObjectInputStream(new FileInputStream(tabledata));
data = (Object[][]) in.readObject(); //explict cast required
in.close();

Because this stores all data as one big chunk I don't think it is possible to just read/write one element. You would have to resort to counting bytes of stored objects and then skip to right position. If you would really need to store huge amount of table data I would use some relational database as backend. Otherwise I wouldn't bother with such optimization. Just rewrite everything on save.