java JDBC ArrayIndexOutOfBoundsException when delete, update

Question

So i try to create a JTable which connect to SQL server database by JBDC, and have a function like insert, delete, and edit the data. It work well with insert but update, delete. Can you guys show me why i got ArrayIndexOutOfBoundsException: -1 and how to fix it. Here 's my code. Book here is a class extends JFRAME

public Book() {
    initComponents();

    model.addColumn("ID");
    model.addColumn("Name");
    model.addColumn("Type");

    jTable1.setModel(model);
    displayTable();
    jTable1.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
        @Override
        public void valueChanged(ListSelectionEvent e) {
            int row = jTable1.getSelectedRow();

            txtName.setText(jTable1.getValueAt(row, 1).toString());
            txtType.setText(jTable1.getValueAt(row, 2).toString());

        }
    });

}

public void displayTable() {
    try {
        model.setRowCount(0);
        ConnectToSQL sql = new ConnectToSQL();
        connection = sql.getConnection();
        st = connection.createStatement();
        ResultSet result = st.executeQuery("SELECT * FROM BOOK");
        while (result.next()) {
            model.addRow(new Object[]{result.getInt("id"), result.getString("name"), result.getString("type")});
        }

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }
}

private void btnUpdateActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    int row = jTable1.getSelectedRow();
    String id = jTable1.getValueAt(row, 0).toString();
    try {
        // TODO add your handling code here:
        st.executeUpdate("Update Book set name ='" + txtName.getText() + "',type='" + txtType.getText() + "' where id =" + id);
        displayTable();

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }

}

private void btnDeleteActionPerformed(java.awt.event.ActionEvent evt) {
    // TODO add your handling code here:
    int row = jTable1.getSelectedRow();
    String id = jTable1.getValueAt(row, 0).toString();
    try {
        // TODO add your handling code here:
        st.executeUpdate("Delete from book where id =" + id);
        displayTable();

    } catch (SQLException ex) {
        Logger.getLogger(Book.class.getName()).log(Level.SEVERE, null, ex);
    }

}

Answer 1

You get this error, because you don't select any row, so to avoid this problem you have to use :

if(jTable1.getSelectedRow() != -1){
   int row = jTable1.getSelectedRow();
   String id = jTable1.getValueAt(row, 0).toString();
   //rest of your code here
}else{
   //show an error for example, no row is selected
}

---

Note

Instead of :

st.executeUpdate("Update Book set name ='" + txtName.getText() + "',type='" + txtType.getText() + "' where id =" + id);

You have to use PreparedStatement to avoid any syntax error or SQL Injection

For example :

String query = "Update Book set name = ?, type=? where id =?";

try (PreparedStatement update = connection.prepareStatement(query)) {

    update.setString(1, txtName.getText());
    update.setString(2, txtType.getText());
    update.setInt(3, id);

    update.executeUpdate();
}

Another thing, your id is an int so you can't set a String to your query like you do you have to set an int :

String id = jTable1.getValueAt(row, 0).toString();

Instead you have to use :

int id = Integer.parseInt(jTable1.getValueAt(row, 0).toString());