如何从SqlServer填充JComboBox

Question

I am trying to populate a JComboBox from data in SqlServer. I am using WindowBuilder if that makes a difference. This is the code I have so far. I am very new to Java so I don't have any idea what to do.

import java.awt.EventQueue;
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTable;

public class Customer extends  JFrame{

private JFrame frame;
private JTable table;
private JTable tblInformation;
private JTable tblHistory;

/**
 * Launch the application.
 */
public static void NewScreen()
{
    EventQueue.invokeLater(new Runnable() {
        public void run() {
            try {
                Customer window = new Customer();
                window.frame.setVisible(true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
}
/**
 * Create the application.
 */
public Customer() {
    initialize();
}

/**
 * Initialize the contents of the frame.
 */
private void initialize() {
    frame = new JFrame();
    frame.setBounds(100, 100, 819, 656);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.getContentPane().setLayout(null);

    JComboBox comboBox = new JComboBox();
    comboBox.setBounds(372, 28, 152, 22);
    frame.getContentPane().add(comboBox);

    JLabel lblCustomer = new JLabel("Select customer");
    lblCustomer.setFont(new Font("Tahoma", Font.PLAIN, 16));
    lblCustomer.setBounds(245, 30, 121, 16);
    frame.getContentPane().add(lblCustomer);

    JLabel lblCustomerInformation = new JLabel("Information");
    lblCustomerInformation.setFont(new Font("Tahoma", Font.PLAIN, 16));
    lblCustomerInformation.setBounds(12, 74, 92, 16);
    frame.getContentPane().add(lblCustomerInformation);

    JLabel lblHistory = new JLabel("History");
    lblHistory.setFont(new Font("Tahoma", Font.PLAIN, 16));
    lblHistory.setBounds(12, 334, 56, 16);
    frame.getContentPane().add(lblHistory);

    JButton btnEdit = new JButton("Edit");
    btnEdit.setBounds(12, 569, 97, 25);
    frame.getContentPane().add(btnEdit);

    JButton btnExit = new JButton("Exit");
    btnExit.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            Welcome.main(null);
        }
    });
    btnExit.setBounds(690, 569, 97, 25);
    frame.getContentPane().add(btnExit);

    JButton btnAdd = new JButton("Add");
    btnAdd.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent arg0) 
        {
            String custIDString, firstName, lastName, companyName, phoneNumber, street, city, state, zip;
            int custID; 

            custIDString = JOptionPane.showInputDialog(null,"Enter customer ID", "Customer ID", JOptionPane.INFORMATION_MESSAGE);
            custID = Integer.parseInt(custIDString);

            firstName = JOptionPane.showInputDialog(null,"Enter first name", "First Name", JOptionPane.INFORMATION_MESSAGE);
            lastName = JOptionPane.showInputDialog(null,"Enter last name", "Last Name", JOptionPane.INFORMATION_MESSAGE);
            companyName = JOptionPane.showInputDialog(null,"Enter company name", "Company Name", JOptionPane.INFORMATION_MESSAGE);
            phoneNumber = JOptionPane.showInputDialog(null,"Enter phone number (xxx-xxx-xxx)", "Phone Number", JOptionPane.INFORMATION_MESSAGE);
            street = JOptionPane.showInputDialog(null,"Enter street", "Street", JOptionPane.INFORMATION_MESSAGE);
            city = JOptionPane.showInputDialog(null,"Enter city", "City", JOptionPane.INFORMATION_MESSAGE);
            state = JOptionPane.showInputDialog(null,"Enter state", "State", JOptionPane.INFORMATION_MESSAGE);
            zip = JOptionPane.showInputDialog(null,"Enter zip", "Zip", JOptionPane.INFORMATION_MESSAGE);
        }


    });
    btnAdd.setBounds(235, 569, 97, 25);
    frame.getContentPane().add(btnAdd);

    table = new JTable();
    table.setBounds(257, 168, 137, -66);
    frame.getContentPane().add(table);

    tblInformation = new JTable();
    tblInformation.setBounds(12, 96, 422, 156);
    frame.getContentPane().add(tblInformation);

    tblHistory = new JTable();
    tblHistory.setBounds(12, 357, 422, 177);
    frame.getContentPane().add(tblHistory);

    JButton btnDelete = new JButton("Delete");
    btnDelete.setBounds(474, 569, 97, 25);
    frame.getContentPane().add(btnDelete);
}
public class TestComboBox extends JComboBox
{
    private Connection sqlCon;
    private Statement st;

    public TestComboBox()
    {
        super();

        initComponents();
    }
    private void initComponents()
    {
        try
        {
            st = sqlCon.createStatement();
            loadComboBox();
        }
        catch (SQLException sqle)
        {
            System.out.println(sqle);
        }
    }
    public void loadComboBox()
    {
        this.removeAllItems();
        this.addItem("Please select");
        try
        {
            ResultSet rs = st.executeQuery("select FirstName, LastName from Customer");
            while (rs.next())
            {
                this.addItem(rs.getString("FirstName") + "" + rs.getString("LastName"));
            }
        }
        catch (SQLException sqle)
        {
            System.out.println(sqle);
        }
    }

}
}

Answer 1

public void loadCombo(){
    Vector vec = new Vector();

        try {
            resultset = //"resultst from database";
            while (resultset.next()) {
                vec.add(resultset.getString("table column"));
                }
                 yourCombo.setModel(new DefaultComboBoxModel(vec)); 
        } catch (Exception ex) {
            ex.printStackTrace();
        }

    }

well here is an example, what im doing here is getting values from resultset putting the values into a vector then im adding the vector inside the combobox try this.

Answer 2

Have you heard about overriding toString method in classes? I'll try to explain.

If you have a class named Customers and attributes for this class are firstName and lastName (with setters and getters), then you could override toString method in Customers class like this:

@Override
public String toString() {
    return firstName;
}

Then you could create a class Example that returns a DefaultComboBoxModel like this:

public static DefaultComboBoxModel getCustomerModel() {
    DefaultComboBoxModel model = new DefaultComboBoxModel();
    ResultSet rs = st.executeQuery("select FirstName, LastName from Customer");
    while (rs.next()) {
        Customer c = new Customer();
        c.setFirstName(rs.getString("FirstName"));
        c.setLastName(rs.getString("LastName"));
        model.addElement(c);
    }
    return model;
}

Finally set your combobox model like this:

myComboBox.setModel(Example.getCustomerModel());

So in myComboBox you will see only the firstName of the customer and if you want to obtain a Customer from myComboBox object, then:

Customer c = (Customer) myComboBox.getSelectedItem();

Regards.