Question

I’m trying to create a GUI program, simple LOGIN maintenance. I have 4 gui components namely: jlabel, jtextfield, jpasswordfield and jbutton. so far, this is my code:

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.swing.*;


public class BankGui extends JApplet implements ActionListener{

// GUI components
JLabel lblUser, lblPass;
JTextField txtUser;
JPasswordField txtPass;
JButton btnOk, btnClear;

// connections to MYSQL
private static Connection connection = null;
private static Statement statement = null;
private static ResultSet resultSet = null;
//public static Scanner in = new Scanner(System.in);

public void init(){
    Container c = getContentPane();
    c.setLayout( new FlowLayout() );

    lblUser = new JLabel( "Username: " );
    c.add( lblUser );
    txtUser = new JTextField( 10 );
    c.add( txtUser );

    lblPass = new JLabel( "Password:" );
    c.add( lblPass );
    txtPass = new JPasswordField( 10 );
    c.add( txtPass );

    btnOk = new JButton( "OK" );
    btnOk.addActionListener( this );
    c.add( btnOk );
}

@Override
public void actionPerformed(ActionEvent e) {
    // TODO Auto-generated method stub
    if( btnOk ){

    }
}

public void connect(){

    try {
        Class.forName("com.mysql.jdbc.Driver");
        connection = DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/USERS", "root", "root");
        statement = connection.createStatement();
        resultSet = statement
                .executeQuery("SELECT lname, fname FROM employees");

    } catch (Exception e) {
        e.printStackTrace();
    }

}


}

But I’m stuck in the method actionperformed and my connect method. I don’t know what to put there to validate if that person who logged in is an authorized user or not.

Answer 1

You can’t perform SQL operation with Applet please change it to Java application (extends the Frame/JFrame). Read this article – What Applets Can and Cannot Do.

You have to write SELECT statement with WHERE clause.

String sql="SELECT userName FROM employees WHERE UserName=? and Password=?";

EDIT:

Register the JDBC driver in static block

 static {
   try{
       Class.forName("com.mysql.jdbc.Driver");
   }catch(Exception ex) { 
       System.err.println(ex);
   }
 }

and write code in actionPerformed method:

PreparedStatement stmt=null;
boolean isFound=false;
try{
   connection = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/USERS", "root", "root");
   String sql="SELECT userName FROM employees WHERE UserName=? and Password=?";
   stmt=connection.prepareStatement(sql);
   stmt.setString(1,txtUser.getText());
   stmt.setString(2,txtPass.getPassword());             
   resultSet=stmt.executeQuery();
   if(resultSet.next()){
     isFound=true;
   }
  //     
}catch(SQLException ex){
   System.err.println(ex);
}finally{
  if(stmt!=null){
      try{ 
         stmt.close();
      }catch(Exception ex) { /* */ }
  }
 if(connection!=null){
      try{ 
         connection.close();
      }catch(Exception ex) { /* */ }
  }
}