No data found Java exception

Question

I'm new to Java and working on a project. i am trying to retrieve data from MS Access with the use of Netbeans. It was all working fine untill i reinstalled my operating system. Now wen i run the code I get this error. Your help and advice would be much appreciated

java.sql.SQLException: No data found
    at sun.jdbc.odbc.JdbcOdbc.standardError(JdbcOdbc.java:7138)
    at sun.jdbc.odbc.JdbcOdbc.SQLDriverConnect(JdbcOdbc.java:3073)
    at sun.jdbc.odbc.JdbcOdbcConnection.initialize(JdbcOdbcConnection.java:323)
    at sun.jdbc.odbc.JdbcOdbcDriver.connect(JdbcOdbcDriver.java:174)
    at java.sql.DriverManager.getConnection(DriverManager.java:582)
    at java.sql.DriverManager.getConnection(DriverManager.java:185)
    at connect.ConnectDB(connect.java:24)
    at StaffLogin.formWindowOpened(StaffLogin.java:125)
    at StaffLogin.access$000(StaffLogin.java:13)
    at StaffLogin$1.windowOpened(StaffLogin.java:47)
    at java.awt.Window.processWindowEvent(Window.java:1859)
    at javax.swing.JFrame.processWindowEvent(JFrame.java:279)
    at java.awt.Window.processEvent(Window.java:1820)
    at java.awt.Component.dispatchEventImpl(Component.java:4630)
    at java.awt.Container.dispatchEventImpl(Container.java:2099)
    at java.awt.Window.dispatchEventImpl(Window.java:2475)
    at java.awt.Component.dispatchEvent(Component.java:4460)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
    at  java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
    at  java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

This is the code, I have left out the 'generated code' and the 'look and feel' also. please let me know if these are needed. Thanks.

import java.sql.*;
import javax.swing.*;

public class StaffLogin extends javax.swing.JFrame {

Connection conn = null;
ResultSet rs = null;
PreparedStatement pst = null;

/**
 * Creates new form StaffLogin
 */
public StaffLogin() {
    initComponents();
}
   private void formWindowOpened(java.awt.event.WindowEvent evt)  {                                  
    // TODO add your handling code here:
    conn = connect.ConnectDB();
}                                 

private void cmdloginMouseClicked(java.awt.event.MouseEvent evt)  {                                      
    // TODO add your handling code here:
    conn = connect.ConnectDB();
   String u = txtusername.getText();
   String p = txtpassword.getText();

    String sql = "SELECT * FROM Staff_Table WHERE Firstname='" + u+"' and Password='"+ p+"'";
    try{
        pst = conn.prepareStatement(sql);
        rs = pst.executeQuery();
        if (rs.next()){
            JOptionPane.showMessageDialog(null,"Correct Password");
            Interface i = new Interface();
            i.setVisible(true);

        }
        else
            JOptionPane.showMessageDialog(null,"Invalid Username or Password");
    }
    catch(Exception e){
        JOptionPane.showMessageDialog(null, e);
    }
}                                     

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {

        public void run() {
            new StaffLogin().setVisible(true);
        }
    });
}
// Variables declaration - do not modify                     
private javax.swing.JButton cmdlogin;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JPanel jPanel1;
private javax.swing.JPasswordField txtpassword;
private javax.swing.JTextField txtusername;
// End of variables declaration                   

}

Answer 1

It is not central to your problem, but this line

String sql = "SELECT * FROM Staff_Table WHERE Firstname='" + u+"' and Password='"+ p+"'";

is a major security hole. Even though you are "using" PreparedStatements, as you are "text" building strings with parameter passed values, you are setting yourself up for a SQL injection attack.

Instead do

String sql = "SELECT * FROM Staff_Table WHERE Firstname=? and Password=?"
try{
    pst = conn.prepareStatement(sql);
    pst.setString(1, u);
    pst.setString(2, p);
    rs = pst.executeQuery();
    if (rs.next()){
        JOptionPane.showMessageDialog(null,"Correct Password");
        Interface i = new Interface();
        i.setVisible(true);

    }
    else
        JOptionPane.showMessageDialog(null,"Invalid Username or Password");
}
catch(Exception e){
    JOptionPane.showMessageDialog(null, e);
}

That way users with names or passwords like "Robert'; DROP TABLE Staff_Table; --" won't become a nightmare in the future.

If you don't understand why this is an issue, consider the scenario where the above "Robert..." user exists.

String u = "Robert'; DROP TABLE Staff_Table; --";
String p = "haha";
String sql = "SELECT * FROM Staff_Table WHERE Firstname='" + u+"' and Password='"+ p+"'";

becomes

String sql = "SELECT * FROM Staff_Table WHERE Firstname='" 
  + "Robert'; DROP TABLE Staff_Table; --" 
  + "' and Password='"+ p+"'";

or simply

String sql = "SELECT * FROM Staff_Table WHERE Firstname='Robert'; DROP TABLE Staff_Table; --' and Password='haha';

which gets executed as a compound SQL statement, consisting of the three SQL statements

SELECT * FROM Staff_Table WHERE Firstname='Robert';
DROP TABLE Staff_Table;
--' and Password='haha';

(note the last line is a SQL comment, as it starts with --).

Answer 2

This typically occurs when you try to read the value of a column multiple times. For example, this may throw "No data found":

ResultSet rs = statement.executeQuery(sql);
while (rs.next()) {
    if ("value1".equals(rs.getString("mycolumn")) || "value2".equals(rs.getString("mycolumn"))) {

This way it works fine:

ResultSet rs = statement.executeQuery(sql);
while (rs.next()) {
    String value = rs.getString("mycolumn");
    if ("value1".equals(value) || "value2".equals(value)) {

Answer 3

My best guess is that someone else created the ODBC data source on your old machine, and you haven't created it on your new machine.

Go here:

Control Panel -> System & Security -> Administrative Tools -> Data Sources (ODBC)