使用来自 MySQL 的数据填充 JComboBox

Question

I have a table called 'supplier' which has two columns 'suppID' and 'suppName'.

I want to pull the data from suppName and fill it into a JComboBox in a way that will keep the contents up to date, meaning if a new row inserted or deleted the JComboBox will be showing the data exactly as it is stored in the table at the time of opening it

        addStock.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent ae) {
            int result = JOptionPane.showConfirmDialog(null,addStockPanel,"Add new stock", JOptionPane.OK_CANCEL_OPTION);
            try{
                //Connect to DB
                Connection conn = CatalogueDB.getConnection();
                //Prepare statement to pull data
                Statement pull = conn.createStatement();


            } catch(Exception e){System.out.println("Error adding supplier");}
            //Finish by printing a message to say the insert has worked.
            finally{
                System.out.println("Insert Completed.");

The only idea that comes to mind with my level of knowledge is to do a select statement from the table then store that in a string, but as I insert data I would constantly have to add more strings to accommodate the extra information.

Answer 1

I have no idea how you created your combobox since you neglected to post the code, but in short, to keep the combobox updated every time you add a new supplier, you can use the following logic (actual implementation is up to you):

In your try statement (where you are actually attempting to add a new supplier to your table), follow the execution of the SQL statement with something like:

try
{
    //Connect to DB
    Connection conn = CatalogueDB.getConnection();
    //Prepare statement to push new supplier data
    Statement push = conn.createStatement();

    // adds new supplier name
    model.addElement(<name of supplier>);
    // notifies combobox that the underlying model has changed
    // box will be repainted automatically
    model.fireContentsChanged();
}
catch(Exception e)
{
    e.printStackTrace();
    // other handling as necessary
}

where model is the model used for your JComboBox , and obviously, the name of the supplier is obtained from whatever variable stores the name of the new supplier you're trying to add.

If an exception prevents the supplier from being added, the part where you add the supplier's name to the combobox will not run, since control passes immediately to the catch portion of your try/catch.

There is no point in running an extraneous select statement to repopulate your combobox after successfully inserting a new supplier when you already have all the data you need.