0

the objective of my code is to bring up the "Gestionnaire" window or to return the error message "Invalid Username / Password" however when I click on login in my Login_form instead of sending me the error "Invalid Username / Password "it returns the error :

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException at javaapplicationhotel2.Login_Form.jButton_LoginActionPerformed(Login_Form.java:426) at javaapplicationhotel2.Login_Form$8.actionPerformed(Login_Form.java:206) at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967) at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308) at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405) at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262) at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279) at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297) at java.desktop/java.awt.Component.processMouseEvent(Component.java:6636) at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342) at java.desktop/java.awt.Component.processEvent(Component.java:6401) at java.desktop/java.awt.Container.processEvent(Container.java:2263) at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012) at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321) at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844) at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918) at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4547) at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488) at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307) at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2762) at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844) at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772) at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721) at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715) at java.base/java.security.AccessController.doPrivileged(AccessController.java:391) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95) at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745) at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743) at java.base/java.security.AccessController.doPrivileged(AccessController.java:391) at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85) at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742) at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203) at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124) at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113) at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109) at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101) at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)

here my code :

    PreparedStatement st;
    ResultSet rs;

    // donnez l'username et le password 
    String username = jTextField_Username.getText();
    String password = String.valueOf(jPasswordField.getPassword());

    // requete indiquant si les identifiants existent 
    String query = "SELECT * FROM 'users' WHERE 'username' = ? AND 'password' = ?";


    try {
        st = (PreparedStatement) Connecter.getConnection().prepareStatement(query);

        st.setString(1, username);
        st.setString(2, password);
        rs = st.executeQuery();

        if(rs.next())
        {
            //ouvrir le gestionnaire 
            Gestionnaire form = new Gestionnaire();
            form.setVisible(true);
            form.pack();
            form.setLocationRelativeTo(null);

            this.dispose();

        }else{
            //erreur  
            JOptionPane.showMessageDialog(null, " Invalid Username / Password", "Login Error",2);
        }

    } catch (SQLException ex) {
        java.util.logging.Logger.getLogger(Login_Form.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }

here my connector : 

package javaapplicationhotel2;

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
import java.sql.*;

/**
 *
 * @author camil
 */




public class Connecter {

  public static Connection getConnection() {
    return con;
}
static Connection con; 


    public Connecter() {
      try{
      Class.forName("com.mysql.cj.jdbc.Driver");
      }catch(ClassNotFoundException e){
          System.err.println(e);


    }
    try{
    con=DriverManager.getConnection("jdbc:mysql://localhost:3306/hotel","root","");
    }catch(SQLException e){System.err.println(e);}
    }
    Connection obtenirconnexion(){return con;}

    PreparedStatement prepareStatement(String select__from_classe) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.



    }


}
javadevfr
  • 7
  • 4

1 Answers1

0

it should be,

public static Connection getConnection() {
   if (instance.con == null)
       instance.con = DriverManager.getConnection("jdbc:mysql://localhost:3306/hotel", "root", "");
 return instance.con;
}
static Connecter instance = new Connecter();
static Connection con;

or 

public static Connecter getConnection(){
   if (connecter == null)
      connecter = new Connecter();
   return connecter;
}

static Connecter connecter;
static Connection con;
//rest of the code
Erwin
  • 460
  • 2
  • 6