java GUI simple login back end mysql

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.

For anyone in the future, here's a simple tutorial on how to create a simple GUI login screen using java and mysql — ThePCWizard
– ThePCWizard, Commented Jan 4, 2013 at 11:03

KV Prajapati · Accepted Answer · 2012-07-12 06:49:11Z

2

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) { /* */ }
  }
}

edited Jul 12, 2012 at 6:49

answered Jul 12, 2012 at 6:29

KV Prajapati

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2 Comments

user1410081 Over a year ago

am I to put that string sql in my connect method or actionperformed?

user1410081 Over a year ago

I already changed it to JFrame, how am I going to display my textfields and button?

Rahul Agrawal · Accepted Answer · 2012-07-12 06:58:59Z

0

Change your code to this

        @Override
        public void actionPerformed(ActionEvent e) {
            // TODO Auto-generated method stub
            if (e.getActionCommand().equals("OK")){
                     if(connect(txtUser.getText(), txtPass.getText())) {
                                // Valid
                     }
                     else {
                           //Invalid
                     }

            }
        }

        public boolean connect(String usr, String pwd){

            try {
                Class.forName("com.mysql.jdbc.Driver");
                connection = DriverManager.getConnection(
                            "jdbc:mysql://localhost:3306/USERS", "root", "root");
                 PreparedStatement ps= connection.prepareStatement("SELECT lname, fname FROM employees where username=? and password =?");
                 ps.setString(1,usr);
                 ps.setString(2,pwd);

                resultSet = ps.executeQuery();

              if(resultSet.next()) {
                       return true;
              }

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

    return false;
        }

edited Jul 12, 2012 at 6:58

answered Jul 12, 2012 at 6:35

Rahul Agrawal

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10 Comments

Lion Over a year ago

Be careful. You're wide open for SQL attacks without using PrepareStatement.

user1410081 Over a year ago

Hi thanks for the reply. I got an error in if ( btnOk ) . my btnOk is jbutton. not boolean

user1410081 Over a year ago

@Lion What am I going to do to prevent sql attacks?

Lion Over a year ago

You should always use parameterized query with the help of PrepareStatement that will prevent you SQL query from SQL injection like SELECT lname, fname FROM employees WHERE UserName=? and Password=?.

Rahul Agrawal Over a year ago

check above changed code, also use PrepareStatement to execute select query to get rid from SQL Injection.

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