Handling exceptions

Question

Hi all,
i have this slight problem, i'm trying to handle accessing a databse from a button click, i'm trying to simulate somebody logging on to a network. the code is as follows;
*@author James Taylor
*@version 30-11-2003
*Logon gui
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.sql.*;
public class LogonUI extends JFrame {
     //instance variables
     private JLabel userNameL;
     private JPasswordField password;
     private JButton logon;
     ButtonHandler handler;
     Connection con;
     Statement stmt;
      *Constructor initialises and creates UI, adds functionality to the button.
     public LogonUI() throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException{
          super("Employee Logon");
          Container c = getContentPane();
          c.setLayout(new FlowLayout() );
          //handles what happens when user presses the button
           handler = new ButtonHandler();
          userNameL = new JLabel("Please Enter Password:");
          c.add(userNameL);
          password = new JPasswordField(15);
          c.add(password);
          logon = new JButton( "Logon" );
          //anonymous inner class that is created once the button is pressed.
          //it connects to database to validate user
          logon.addActionListener( handler );
          c.add(logon);
          c.setBackground( Color.pink );
          setDefaultCloseOperation(DISPOSE_ON_CLOSE);
          setSize(250,150);
          setVisible(true);
      *class that opens connection to validate user
     private class ButtonHandler implements ActionListener {
          public void actionPerformed(ActionEvent ae)throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException{
               try{
                    boolean isValidUser = false;
                    //Load mysql driver
                     Class.forName("com.mysql.jdbc.Driver").newInstance();
                     //make a connection
                    String url = "jdbc:mysql://localhost/flight";
                    con = DriverManager.getConnection(url)
                    //Create and instantiate a statement obj
                    stmt = con.createStatement();
                    //get a result set
                    ResultSet rs = stmt.executeQuery("SELECT Password FROM employees");
                    //Iterate through the result set
                    while ( rs.next() ){     
                         String savedPassword = rs.getString("Password");
                         if (password.getText().equals(savedPassword) ){
                              isValidUser = true;
                              JOptionPane.showMessageDialog(null,"Yipeeeee");
                    if (isValidUser == false){
                         JOptionPane.showMessageDialog(null,"Invalid Password");     
                    stmt.close();
                    con.close();
               }catch(Exception e){ e.printStackTrace();}
          public static void main (String[] args) throws SQLException, ClassNotFoundException, IllegalAccessException, InstantiationException{
          LogonUI testAirApp = new LogonUI();
}When the user presses the button the app tries to validate the user.
I have not been able to test the code due to SQL Exceptions thrown in the handler class, and when i try and throw them up from here i get;
LogonUI.java:52: actionPerformed(java.awt.event.ActionEvent) in LogonUI.ButtonHandler cannot implement actionPerformed(java.awt.event.ActionEvent) in java.awt.event.ActionListener; overridden method does not throw java.lang.InstantiationExceptionAny ideas on my code and how to handle these exceptions will be very appreciated. Regards, James

Answer 1

More your public void actionPerformed(ActionEvent ae) does not throw SQLException, ClassNotFoundException and IllegalAccessException.
You catches exceptions in method code.
Remove any exceptions from method declaration