通过jList从数据库中删除对象

Question

I am building a Java GUI application in Netbeans intended to represent a digital till system (or ePOS till).

I need to be able to view a list of users through a jList, as well as modify and remove them. Each user is an object built with a User model class and represents a record on a mySQL accdb database.

I have successfully managed to add users to the database, and populate the jList with the contents of an ArrayList containing User objects, but I don't understand how to remove the user I have selected in jList from the database.

The following is code to remove users from the db:

//  removes users from the database
public void removeUser (User dbUser) {

    try (Connection conn = setupConnection()) {

        // create SQL statement
        Statement stmt = conn.createStatement();

        // SQL query in string variable
        String sql = "DELETE FROM Users " +
                    "WHERE employee_number = " +
                     dbUser.getEmployeeNumber();

       // execute query on database
        stmt.executeUpdate(sql); 

    } catch (Exception ex) {

        String message = ex.getMessage();
        System.out.println("dbUser error: " + message);

    }

}

I understand this somewhat, but being able to target a specific user through jList and remove it from the database is something I cannot get my head around.

I won't post my code for adding users and populating the jList unless asked, for the sake of clarity.

Thank you.

Answer 1

I was able to solve my issue with this solution:

1. Save the index of item in the list I wanted to remove to a variable.
2. Get the model element at the same index position by targeting the variable.
3. Creating an instance of the user object based on the selected index, remembering to cast the the User object type.
4. Finally, removing the database entry and the list entry.

This is the code:

// validate that an item is selected
    if (user_lst.isSelectionEmpty()) {

        JOptionPane.showMessageDialog(null, "You haven't selected an account to remove from the list.");

    } else {



        // target object at list index
        int index = user_lst.getSelectedIndex();

        // remove object at list index
        model.getElementAt(index);

        // create instance of user based on selected index
        User u = (User) model.getElementAt(index);


        if (index < 0) {

            System.out.println("jList error: There are no items");

        } else {

            db.removeUser(u);
            model.remove(index);

        }

        // refresh list model
        user_lst.setModel(model);

        // confirm user was removed
        JOptionPane.showMessageDialog(null, "Account removed");

    }