Update Jtable using Defaulttablemodel

Question

I understand that the use of Defaulttablemodel is almost abhorrent, however, I used this model and now I have no time to change to a Tablemodel (which I haven’t learned to use yet), is there any way to update a table of a class in the View, after a create method in Dao? The system is in Java, using Javax.Swing MVC.

Creation of the main screen and Jtable data

@Override
public void actionPerformed(ActionEvent ae) {
    if (ae.getSource().equals(btnentrar)) {

        if (txtsenha.getPassword().length == 0 || txtuser.getPassword().length == 0) {
            JOptionPane.showMessageDialog(frame, "Preencha os campos");
        } else {

            UserDao userDao = new UserDao();
            Usuario usuario = new Usuario();
            usuario = userDao.Login(new String(txtuser.getPassword()), new String(txtsenha.getPassword()));

            if (usuario != null) {
                JOptionPane.showMessageDialog(frame, "Conectado");
                Principal principal = new Principal();
                principal.initComponents(usuario);
                principal.carregarDadosProdutosJTable();
                frame.dispose();
            } else {
                JOptionPane.showMessageDialog(frame, "Não foi possível efetuar login.");
            }

        }

    }
}

Package:View Class:Login

A simple login screen, this is the Login button action.

Method to load data to Jtable

public void carregarDadosProdutosJTable() {
    ItemDao itemDao = new ItemDao();
    DefaultTableModel model = (DefaultTableModel) table.getModel();
    model.setRowCount(0);
    ArrayList<Item> itens = (ArrayList<Item>) itemDao.listarProdutos();
    for (Item c : itens) {
        model.addRow(new Object[]{c.getCodigo(), c.getDescricao(), c.getCategoria(), c.getEstoque()});
    }
}

Package:View Class:Home

If I just try to call this method again, Netbeans displays a Null error in the third line of that code (Defaultablemodel model = ...)

Save New Item Method

public void salvarItem(Item item) {
    try {
        // cria um preparedStatement
        pstm = con.prepareStatement("insert into produto (prodescricao,procategoria,proestoque) values (?,?,?)");

        pstm.setString(1, item.getDescricao());
        pstm.setString(2, item.getCategoria());
        pstm.setInt(3, item.getEstoque());
        pstm.execute();
        pstm.close();
        con.close();
        JOptionPane.showMessageDialog(null, "Item registrado com sucesso.");
    } catch (SQLException erro) {
        JOptionPane.showMessageDialog(null, "Erro de sql " + erro.getMessage());
    }
}

Package:Dao Class:Itemdao

Ideally, I think it would be to update after saving a new item, since it would change the list of products, or items, and the old table would no longer be correct. Is there any way to do this without having to implement a Tablemodel? I am aware of how much better it is to use a Tablemodel, but I do not have much time on this project. I am a beginner in the area, if you can simplify the explanation thank you.

Answer 1

First, I recommend declaring the Jtable model in the class, so whenever you need it, just do it table.getModel(model) The error is due to not having declared Jtable in the constructor (public (classe utilizada)) In class you must do DefaultTableModel model = new DefaultTableModel(String[](Seus campos) and in the builder do (nomedatabela) = new JTable(model) This should solve the problem. If not solve, I beg no excuse but I am also beginner

`

Answer 2

public void carregarDadosProdutosJTable() {
    ItemDao itemDao = new ItemDao();

    table.getColumnModel().getColumn(0).setPreferredWidth(4);
    table.getColumnModel().getColumn(1).setPreferredWidth(220);
    table.getColumnModel().getColumn(2).setPreferredWidth(40);
    table.getColumnModel().getColumn(3).setPreferredWidth(40);            
    DefaultTableModel model = (DefaultTableModel) table.getModel();
    model.setRowCount(0);
    ArrayList<Item> itens = (ArrayList<Item>) itemDao.listarProdutos();

    try{
        for (Item c : itens) {
        model.addRow(new Object[]{c.getCodigo(), c.getDescricao(), c.getCategoria(), c.getEstoque()});
    }
    }catch(Exception erro){
        erro.printStackTrace();
         JOptionPane.showMessageDialog(null, "A tabela não pôde ser carregada");
     }
}

See which error will appear, or thing, puts your method that lists the items