populating a jcombobox with database information

Question

I know I am missing something simple, I think in getting the combobox to access the array.

package my.freelancebillingapp;

import java.sql.; import java.sql.Connection; import java.sql.DriverManager; import java.util.ArrayList; import javax.swing.;

public class billingInfoUI extends javax.swing.JFrame {

public billingInfoUI() {
    initComponents();
}

@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    hoursWorked = new javax.swing.JTextField();
    jLabel1 = new javax.swing.JLabel();
    flatRate = new javax.swing.JTextField();
    jScrollPane1 = new javax.swing.JScrollPane();
    workType = new javax.swing.JList();
    jScrollPane2 = new javax.swing.JScrollPane();
    jList2 = new javax.swing.JList();
    jButton1 = new javax.swing.JButton();
    jButton2 = new javax.swing.JButton();
    jButton3 = new javax.swing.JButton();
    jComboBox1 = new javax.swing.JComboBox();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jPanel1.setBorder(javax.swing.BorderFactory.createTitledBorder(null, "Billing Information", javax.swing.border.TitledBorder.CENTER, javax.swing.border.TitledBorder.ABOVE_BOTTOM, new java.awt.Font("Bleeding Cowboys", 0, 48))); // NOI18N

    javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
    jPanel1.setLayout(jPanel1Layout);
    jPanel1Layout.setHorizontalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 457, Short.MAX_VALUE)
    );
    jPanel1Layout.setVerticalGroup(
        jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 0, Short.MAX_VALUE)
    );

    hoursWorked.setHorizontalAlignment(javax.swing.JTextField.CENTER);
    hoursWorked.setText("Hours Worked");
    hoursWorked.setBorder(null);

    jLabel1.setText("Or");

    flatRate.setHorizontalAlignment(javax.swing.JTextField.CENTER);
    flatRate.setText("Flat Rate");
    flatRate.setBorder(null);

    workType.setBorder(javax.swing.BorderFactory.createTitledBorder(javax.swing.BorderFactory.createEtchedBorder(), "Work Type", javax.swing.border.TitledBorder.CENTER, javax.swing.border.TitledBorder.TOP));
    workType.setModel(new javax.swing.AbstractListModel() {
        String[] strings = { "Web Design", "Graphic Design", "Consulting" };
        public int getSize() { return strings.length; }
        public Object getElementAt(int i) { return strings[i]; }
    });
    workType.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
    jScrollPane1.setViewportView(workType);

    jList2.setBorder(javax.swing.BorderFactory.createTitledBorder(javax.swing.BorderFactory.createEtchedBorder(), "Any Extras?", javax.swing.border.TitledBorder.CENTER, javax.swing.border.TitledBorder.TOP));
    jList2.setModel(new javax.swing.AbstractListModel() {
        String[] strings = { "Blog", "Forum", "Templating", "Rush Delivery" };
        public int getSize() { return strings.length; }
        public Object getElementAt(int i) { return strings[i]; }
    });
    jScrollPane2.setViewportView(jList2);

    jButton1.setText("Save");
    jButton1.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseClicked(java.awt.event.MouseEvent evt) {
            jButton1MouseClicked(evt);
        }
    });

    jButton2.setText("Invoice");

    jButton3.setText("Close");
    jButton3.addMouseListener(new java.awt.event.MouseAdapter() {
        public void mouseClicked(java.awt.event.MouseEvent evt) {
            jButton3MouseClicked(evt);
        }
    });
    jButton3.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton3ActionPerformed(evt);
        }
    });

    jComboBox1.setModel(customers);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(89, Short.MAX_VALUE)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                    .addComponent(hoursWorked, javax.swing.GroupLayout.PREFERRED_SIZE, 83, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(48, 48, 48)
                    .addComponent(jLabel1)
                    .addGap(1, 1, 1))
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                    .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 142, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(31, 31, 31)))
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createSequentialGroup()
                    .addGap(18, 18, 18)
                    .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 120, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(layout.createSequentialGroup()
                    .addGap(49, 49, 49)
                    .addComponent(flatRate, javax.swing.GroupLayout.PREFERRED_SIZE, 56, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addGap(79, 79, 79))
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addGap(62, 62, 62)
            .addComponent(jButton1)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 103, Short.MAX_VALUE)
            .addComponent(jButton2)
            .addGap(79, 79, 79)
            .addComponent(jButton3)
            .addGap(52, 52, 52))
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(134, Short.MAX_VALUE)
            .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 238, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(107, 107, 107))
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(30, 30, 30)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(hoursWorked, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(flatRate, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel1))
            .addGap(20, 20, 20)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 86, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 100, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 40, Short.MAX_VALUE)
            .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addGap(51, 51, 51)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jButton2)
                .addComponent(jButton3)
                .addComponent(jButton1))
            .addContainerGap())
    );

    pack();
}// </editor-fold>

private void jButton3ActionPerformed(java.awt.event.ActionEvent evt) {                                        

}                                        

private void jButton3MouseClicked(java.awt.event.MouseEvent evt) {                                      
    new FreelanceBillingUI().setVisible(true);
    setVisible(false);
}                                    

private void jButton1MouseClicked(java.awt.event.MouseEvent evt) {

String hoursWorkedtxt = hoursWorked.getText(); String flatRatetxt = flatRate.getText(); workType.getSelectedValue(); workType.toString(); Object workTypetxt = workType.getSelectedValue();

if(hoursWorkedtxt.contains("H")){ hoursWorkedtxt = "0"; }else{ flatRatetxt = "0"; }

}

public class CustomerData {

private static final String JDBC_CONNECTION_URL    = "jdbc:mysql://localhost/test";

private static final String DATABASE_USER         = "root";

private static final String DATABASE_PASSWORD    = "root";

private static final String SQL_FETCH_CUSTOMERS = "SELECT custName FROM customers";

private Connection connection = null;


public CustomerData(){
    initConnection();
}


private void initConnection() {
    try {
        //load the mysql driver
        Class.forName("com.mysql.jdbc.Driver");
        //create the database connection
        connection = DriverManager.getConnection(JDBC_CONNECTION_URL, DATABASE_USER, DATABASE_PASSWORD);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }

}

public void closeConnection(){
    if (connection != null) {
        try {
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            connection = null;
        }
    }
}

public ArrayList fetchCustomerData(){
    if (connection != null){
        Statement statement = null;
        try {
            statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(SQL_FETCH_CUSTOMERS);
            return convertResultSetToCustomersArray(resultSet);
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {

            if (statement != null){
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }else{
        System.out.println("NO VALID DATABASE CONNECTION, CAN'T FETCH CUSTOMER DATA!");
    }
    return new ArrayList();
}

private ArrayList convertResultSetToCustomersArray(ResultSet results) throws SQLException{
    ArrayList customers = new ArrayList();

    while (results.next()){
        customers.add(results.getString("custName"));
    }
    return customers;
}

}

private void initData(){
    CustomerData customerData = new CustomerData();

    ArrayList custArrayList = customerData.fetchCustomerData();

    customers = (String[]) custArrayList.toArray(new String[0]);
}

/**
* @param args the command line arguments
*/
public static void main(String args[]) {
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new billingInfoUI().setVisible(true);
        }
    });
}
private String[] customers = null;
private javax.swing.JTextField flatRate;
private javax.swing.JTextField hoursWorked;
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JButton jButton3;
private javax.swing.JComboBox jComboBox1;
private javax.swing.JLabel jLabel1;
private javax.swing.JList jList2;
private javax.swing.JPanel jPanel1;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JList workType;

}

Answer 1

There is too much code there to look at 90% of it is NOT related to adding data in a combo box. You have a dozen other components which clutter the code so we can't see what actually happening with the comobo box.

It you really need help then post a SSCCE.

That is, create a simple frame and load hard coded data into the combo box.

Then create a simple program to read data from the database and use System.out.println(...) to display each value.

Once you've mastered the two basic steps, then put the two programs together to load a combobox dynamically from a database.

Finally add the rest of you components to the frame.

Break you problem down into small, manageable steps and you will be able to debug it easier.

Answer 2

A few points:

• Wading through your code, I don't see a call to initData being made anywhere. Without that call, you wont call your database code. Without the database call, you wont get the data.
• JComboBox does not have a setModel method that takes an array. You can wrap your array in a DefaultComboBoxModel and set that on the model.
• It is good to keep in mind that blocking calls like database access should not be made in the AWT painting thread, and neither should calls that update the GUI be made outside of the AWT thread. You should look into creating your GUI and grabbing your data in separate threads, and making use of SwingUtlities.invokeLater or similar tools to update your GUI.